Research ArticleAdsorption Cooling System Using Metal-Impregnated Zeolite-4A
Somsuk Trisupakitti Jindaporn Jamradloedluk and Songchai Wiriyaumpaiwong
Faculty of Mechanical Engineering Mahasarakham University Kantharawichai District Maha Sarakham 44150 Thailand
Correspondence should be addressed to Somsuk Trisupakitti somsuk rmuyahoocom
Received 28 February 2016 Revised 19 May 2016 Accepted 19 May 2016
Academic Editor Luigi Nicolais
Copyright copy 2016 Somsuk Trisupakitti et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited
The adsorption cooling systems have been developed to replace vapor compression due to their benefits of being environmentallyfriendly and energy savingWe prepared zeolite-4A and experimental cooling performance test of zeolite-water adsorption systemThe adsorption cooling test-rig includes adsorber evaporator and condenser which perform in vacuumatmosphereThemaximumand minimum water adsorption capacity of different zeolites and COP were used to assess the performance of the adsorptioncooling systemWe found that loading zeolite-4A with higher levels of silver and copper increased COPThe Cu6zeolite-4A hadthe highest COP at 056 while COP of zeolite-4A alone was 038 Calculating the acceleration rate of zeolite-4A when adding 6of copper would accelerate the COP at 46
1 Introduction
Cooling systems play important roles in our daily lifelike food preservation air-conditioning system and medi-cal treatment However popular vapor compression refrig-eration systems have a destructive effect on the globalenvironmentmdashthe greenhouse effect [1] This damages theozone level in Earthrsquos atmosphere due to emission of HFCsHCFCs and CFCs commonly used in vapor compressionsystems and use of these refrigerants is perceived as acritical contributor to global warming [1] Therefore alter-native adsorption cooling systems may help to reduce thegreenhouse effect and this alternative technology has someadditional benefits as it can use waste heat sources includingsolar power industrial factories or automobiles [1 2]
Adsorption cooling systems are environmentally friendlyin that the system does not destroy ozone and add to globalwarming [2] because an adsorption cooling system usesnatural refrigerants such as water ammonia methanol andethanol However there are some disadvantages Adsorptionsystems cool in a noncontinuous cycle and the adsorptionrate between the working pairs is not constant That is inthe initial stage the adsorption rate is fast as the surface areaof adsorbent is adequate but after some time the workingpairs reach equilibrium and the surface area is fully occupiedSo the working substance cannot reach the inner regionsof adsorbent and thus leads to slower adsorption rate This
directly leads to lowCoefficient of Performance (COP)Thereare two ways to solve these problems One is to develop a newadsorbent which has better adsorption capacity The other isto improve the physical structure of adsorbent The zeolite-water pair is generally regarded as one of the most suitableadsorbent-adsorbate pairs in these devices [1ndash3]
Accordingly researchers have put extensive efforts tofurther study and develop adsorption refrigeration system toenhance the COP A family of the new composite adsorbentsformed by impregnating inorganic salts into the pores ofzeolite has been developed [1 2] Chan et al reported thata 13XCaCl
2composite adsorbent for adsorption cooling
systems with an ideal COP for a 13XCaCl2-water pair is 078
compared to 054 for zeolite-13X-water pair [4] SimilarlyGrenier et al [5] studied a system using a 20m2 simplesolar collector containing 360 kg of NaX zeolite for a coldstorage plant it transferred only about 188MJm2 when theincident radiation was 178 KJm2 The operation conditionswere a 305K condensation temperature 274K evaporatingtemperature and 391 K regeneration temperatureThe systemcould attain a net solar COP of 011 while its cycle COPwas 038 Tatlier and Erdem-Senatalar also used zeolite-wateras working pair and reported that the system could operatesuccessfully if the ambient temperature is less than 293K[6] Pons and Guilleminot tried to use zeolite composites toreplace zeolite as an adsorbent and two different composites
Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2016 Article ID 4283271 8 pageshttpdxdoiorg10115520164283271
2 Advances in Materials Science and Engineering
(i) 65 zeolite + 35metallic foam and (ii) 70 zeolite + 30natural expanded graphiteThe latter combination performedbetter [7] A similar performance was noted by Hu et al whofound that if the evaporation temperature is set to 269K therequired condition temperature should not exceed 303K [8]
Biloe et al used polyvinyl alcohol mixed with polyethy-lene glycol as bonding agent and graphite mixed with acti-vated carbon as adsorbent in a methane adsorption systemThey found that adsorption of methane was improved dueto the increased ratio of graphite [9] Restuccia et al [10]used 20 bentonite as bonding agent for zeolite Y particlesto enhance heat transfer in a heat exchange tube They foundthat bentonite had no effect on adsorption of zeolite Y andimproved heat transfer rate Zhao et al [11] investigatedzeolite 13X by loading sodium silicate in different portionsfor an adsorption system They found that an increased levelof sodium silicate led to increased heat transfer In additionHu et al developed an adsorption system using heat froman exhaust pipe with an adsorption device based on zeolitemixed with aluminium They found that zeolite-aluminiumfoam augmented the COP of an adsorption system comparedto zeolite alone [8]
Our present work investigated experimentally theadsorption capacity of water on zeolite-4A from Thai claywith silver and copper loading to determine the COP foradsorption and desorption processes
2 Materials and Methods
21 Raw Material Clay was supplied by Mineral ResourcesDevelopment Co Ltd sourced from Ranong Thailand(9∘5710158404310158401015840N 98∘3810158402010158401015840E) Laboratory Reagent (LR) gradesodium hydroxide was used for ion exchange procedure
22 Preparation of Zeolite Type-4A Zeolite-4A was syn-thesized from clay in two processes metakaolinisation andzeolitisation following Chandrasekhar et al [12]
Metakaolinisation heats the clay to a high tempera-ture until it transforms its crystal structure and turns intometakaolinite Zeolitisation drives Na+ ions into the crystalstructure to form zeolite-4A
For our experiments we performed synthesis by calcina-tion at 873K for 3 h until the clay turned into metakaoliniteThen 05 kg of metakaolinite was mixed with 25 L of 35Msodium hydroxide at 363K for 3 h to insert Na+ ions intothe metakaolinite structure The slurry of metakaolinite wasthen filtered and washed several times with distilled water toremove excess unreacted NaOH Then it was filtered againand dried in an air oven at 373K overnight We had studiedthe maximum yield (70) in previous work [13] Thereforethe preparation was done in the same condition before metalloading in this work The chemical reaction in this step is
2Al2Si2O5(OH)4997888rarr 2Al
2Si2O7+ 4H2O (1)
6Al2Si2O7+ 12NaOH
997888rarr Na12(AlO2)12(SiO2)12sdot 27H2O + 6H
2O
(2)
23 Preparation of Metal-Impregnated Zeolite-4A 05 kg ofzeolite-4A was mixed with 25 L of silver nitrate or coppersulfate solution at the desired concentration at 323K for30mins After that the mixture was dried at 343K for 4 daysFinally the calcined material was heated at 573K for 2 h
24 Characterization of RawMaterial and Zeolite-4A Chem-ical compositions of raw kaolin samples were determinedby X-ray fluorescence spectroscopy using a Bruker AXS SRS3400
The crystallinity of the inorganic components was ana-lyzed by XRD (Bruker D8 Germany) with Cu-K
120572radiation
used to record the diffraction spectra The tube voltageand current were 30 kV and 30mA The area of 8 strongdiffraction peaks of the sample was compared to the patternof standard zeolite which was set to be 100
The morphology of samples was observed using a Scan-ning Electron Microscope (Leo 1455 VP UK) using anaccelerating voltage of 15 kV
Brunauer-Emmett-Teller (BET) analysis used aMicrome-ritics surface analyzer (ASAP2020 USA) to determine thespecific surface area of the zeolite and the pore size wascalculated by the Barrett-Joyner-Halenda (BJH) method viadesorption-adsorption of nitrogen gas at 78K
25 Basic Adsorption Cycle A complete adsorption coolingcycle that consists of adsorption (evaporation + cooling)and desorption (condensation + heating) can be explainedwith the help of the Clapeyron diagram in Figure 1 Theidealized cycle begins at point 1 where the maximum amountof refrigerant is adsorbedThe adsorbent is at low temperatureand low pressure at point 1 Along line 1-2 the adsorbentis heated and desorbs refrigerant vapor isosterically Thisstep is isosteric because there will be no refrigerant flowuntil the pressure inside the adsorbent bed becomes equalto or greater than the pressure of the condenser and theamount of desorbed refrigerant is small relative to the totalamount adsorbed Continued heating (line 2-3) desorbsmorerefrigerant forcing it to the condenser until state 3 is attainedat which desorption ceases This second step is isobaricdesorption Then the hot adsorbent is cooled isostericallycausing adsorption and depressurization (line 3-4)When thepressure drops below 119875ev refrigerant in the evaporator startsto boil and flows to the adsorbent bed producing the coolingeffect Cooling of the adsorbent continues until the bed issaturated with refrigerant completing the cycle This process(line 4-1) is isobaric adsorption
The COP of the system can be calculated as reportedin Cacciola and Restuccia [14] As seen from Figure 1 thethermodynamic cycle consists of 4 processes
4 rarr 1 isobaric adsorption (heat of adsorption +sensible cooling)
Advances in Materials Science and Engineering 3
P
Pcond
Pev
Desorption
Resorption
1
2 3
4
Isostericheating
Isostericcooling
Ta1Tg1Ta2 Tg2
T
Wmax Wmin
Figure 1 P-T-W diagram of the basic adsorption cycle [14]
In isosteric heating (1rarr 2) and isobaric desorption (2rarr3) heat is added to the adsorbent bedThe heat supplied to theadsorbent bed for its isosteric heating (1rarr 2) is
11987612= 119898119911(119862119901119911+ 119862119901119908119882max) (1198791198921 minus 1198791198862) (3)
where 119898119911is the mass of adsorbent in kg 119862
119901119911is the specific
heat of adsorbent in kJkg-K and 119862119901119908
is the specific heat ofadsorbate in the adsorbed phase in kJkg-K
The heat necessary for the desorption phase (2rarr 3) hastwo components
The useful refrigeration effect which is the energy thatmust be supplied to the evaporator 119876
119890 is calculated as the
latent heat of evaporation of the cycled adsorbate minus thesensible heat of the adsorbate that is entering the evaporatorat condensation temperature
119876119890= 119898119911(119882max minus119882min) [119871 minus 119862119901119897 (119879119888 minus 119879119890)] (7)
where119862119901119897is the specific heat of adsorbate in liquid phase and
119871 is the heat of evaporation of adsorbate in kJkgFrom the previous equations the COP for cooling opera-
tion can be calculated as the ratio of useful refrigeration effectproduced and heat input to the adsorbent bed
COP =119876119890
11987612+ 11987623
(8)
Table 1 Chemical composition of clay at Ranong province
Component SiO2
Al2O3
SO3
K2O Fe
2O3
CuO weight 522 433 036 218 161 025
26 Experimental Setup Before starting the experiments thelaboratory was prepared according to the procedure givenby Cacciola and Restuccia [14] An overview of the rigcomponents is shown in Figure 2 A known mass of zeolitewas put into the adsorber The adsorber line was connectedto the evaporator and condenser line
System preparation steps before activating the systemare as follows
(1) Turn off every valve(2) Put 01 kg of zeolites into adsorber(3) Put 03 L of water into evaporator(4) Adjust vacuumpressure value of evaporator at 73 kPa(5) For adsorber and condenser adjust vacuum pressure
value at 87 kPa within 20mins
Desorption system tests are as follows
(1) Valve V1
opened slowly to allow the water vaporto flow into the adsorber for 30mins after whichthe system reaches thermodynamic equilibrium ofadsorption
(2) Turn off valve V1
(3) Then begin desorption process by generating heat foradsorber at the designated temperature
(4) After that turn on valves V2 V3 and V
4to allow the
water vapor into condenser which contains refriger-ant to condense vapor into liquid
(5) Collectively store it at evaporator for 30mins afterwhich the system reaches thermodynamic equilib-rium of desorption process
(6) All valves closed
Adsorption system testing valve V1opened slowly to
allow the water vapor to flow into the adsorber for 30minsafter which the system reaches thermodynamic equilibriumof adsorption process and turn off valve V
1
For all steps temperature was recorded by a data loggerThe total amount of water desorbed and adsorbed by zeolitewas read from the balance
3 Results and Discussions
31 Properties of Zeolite-4A The chemical composition ofclay from Ranong province in Thailand is in Table 1 Themain components of the clay samples were oxides of Si andAl but they contain sulfur potassium iron and copperimpurities Therefore zeolite-4A prepared from this clay isalways contaminated with these elements
The XRD patterns of the solid samples are shown andcompared to the pattern of standard zeolite in Figure 3 it can
4 Advances in Materials Science and Engineering
Adsorber
Condenser
Evaporator
V1
V2
V3
V4
Figure 2 Photograph of adsorption refrigeration system
Ranong kaolinSyn Z4AStd Z4A
0100200300400500600700800900
1000
5 10 15 20 25 30 35 40 45 50 55 6002Φ
Figure 3 X-ray diffraction patterns of clay and zeolite-4A
be seen that synthesized clay for zeolite-4A (Z4A) compriseskaolinite as main element and when it was heated at 773Kkaolinite became more crystalized showing a higher peakvalue because organic compounds had evaporated at 773Kand made kaolinite purer Also peak was found along 2axes at the same position as a zeolite-4A reference so weconcluded that clay was transformed to zeolite-4A
When examining microstructure attributes of clay usingScanning Electron Microscope (SEM) we found crystallinestructures arranged in layers see Figure 4(a) Figure 4(b)shows the prepared zeolite-4A which has crystalline angles
Table 2 Specific surface area total pore volume and average porediameter
that corresponded with sharp peaks in the XRD spectrumhaving the crystalline attributes of zeolite-4A
Figure 5 shows the zeolite-4A surface filled with copper(Cu6Z4A) (a) and silver (Ag15Z4A) (b) at 5000xmagnification It can be clearly seen that silver particles werethinly dispersed on the zeolite-4A surface whereas copperparticles aggregated into larger clumps on the surface (a)
Synthesized zeolite-4A was analyzed for quality of poros-ity using adsorption of nitrogen at 78K with Micromeriticschemisorption analyzer model ASAP2020 Pore surface areawas determined using the Brunauer-Emmett-Teller (BET)formula to total pore volume at 119875119875
119900= 097 and average
pore diameter calculated by equation (4 times total pore vol-ume)surface
Figure 6 shows the N2adsorption isotherm of zeolite-4A
at 78Kwhich indicated that the adsorption isothermwas sim-ilar to type IV in the nomenclature IUPAC for mesoporousmaterials Table 2 shows that for synthesized zeolite-4Awhen sodium ions (Na+) were replaced with copper (Cu2+)or silver (Ag+) ions the total pore volume and pore diameterincreased relatively to pure zeolite-4A Cu6Z4A showedthe highest value for surface area (182m2g) total porevolume (00428mLg) and average pore diameter (939 nm)IUPAC defines three types of pore diameter micropore(lt2 nm) mesopore (2ndash50 nm) and macropore (gt50 nm)Our analysis showed that all synthesized zeolite-4A sampleswere mesopore and this indicates that this zeolite-4A couldadsorb water with diameter 028 nm and average poresmaller than the diameter of all zeolites
32 Adsorption and Desorption Behavior Testing adsorptionunder vacuum conditions involved two processes adsorp-tion and desorption Five samples of synthesized adsorbentwere tested Z4A Cu4Z4A Cu6Z4A Ag4Z4A andAg15Z4A Maximum adsorption (119882max) and minimumadsorption (119882min) of zeolite-4A are shown in Figures 7ndash9
Physical adsorption depended on pore diameter andpore volume Generally good adsorption occurred at lowtemperature due to the exothermic process So when the tem-perature was increased the degree of adsorption decreasedFigure 7 shows the water adsorptionmass during adsorptionwe found that when the adsorber temperature increasedadsorption performance ofwater decreased from008 at 315Kto 003 at 318 K and the COP reduced correspondingly
During evaporation after providing heat to adsorber attemperatures from 393 to 478K for 30mins heat from
Advances in Materials Science and Engineering 5
(a) (b)
Figure 4 SEM photograph of clay (a) and zeolite-4A (b)
Figure 7 Effect of adsorption temperature on119882max and COP
007004
002
018
035038
393 435 478
COP
000
005
010
015
020
025
030
035
040
COP
K
Wmin
Figure 8 Effect of desorption temperature on119882min and COP
adsorber was transferred to zeolite-4A until it reached thestable stage After that vapor was expelled from the zeolite-4A and shifted to condenser vapor condensed and collectedin the evaporator
From Figure 8 we see the lowest adsorption weightfor working pairs (zeolite-4A and water) it was found thatheat must be increasingly supplied for adsorber at 478K togain the maximum evaporation from zeolite Kinetic energyof vapor held unequal value when temperature changedWhen the temperature increased vapor mobility increasedso better desorption performance was observed Water wasevaporated faster from adsorber during desorption and ahigher water volume was adsorbed in the absorption step
001 002 002
042
038 038
285 289 294
COP
000
005
010
015
020
025
030
035
040
045
COP
K
Wmin
Figure 9 Effect of condenser temperature on119882min and COP
Figure 9 shows that the water mass adsorbed duringthe exothermic process was little effected by temperaturebetween 285 and 294K Water molecules adsorbed in thezeolite-4A pores could be condensed to liquid at a tem-perature higher than boiling point in the process calledcapillary condensation When the condensation temperatureincreased the saturated vapor pressure within the condenserwas also increased blocking (or hindering) transfer of vaporinto the condenser This led to ineffective desorption and themass of vapor being desorbed was also reducedThese resultswere based on a small-scale experiment so the adsorbedwater mass and COP showed little significant differencebetween 285 and 294K therefore to save energy in vaporcondensation step the condensation temperature was set tomatch the very slightly larger COP at 294K
33 COP of Adsorption Cooling System Investigating adsorp-tion cooling system using referential equation of Cacciolaand Restuccia [14] could determine the COP of the systemThe parameters obtained from maximum and minimumadsorption were adsorber at 305K during adsorption andadsorber at 478K during desorption
Figure 10 shows that copper and silver added to thezeolite-4A significantly affected systemCOPbecause a highermass of water was adsorbed by copper or silver filled zeolite-4A compared to pure zeolite-4A This maximum adsorption(119882max) was increased because size and volume of poreswere also increased However minimum adsorption (119882min)showed no significant difference because the increase ofaverage pore diameter allowed vapor to be evaporated easilyfrom the pores when receiving heat at temperature higherthan the boiling point Our results showed that COPs were056 for Cu6Z4A and 052 for Ag15Z4A whereas COPof Z4A was only 038 showing that adding copper and silvereffectively increased the systemCOP COP of zeolite-4A filledwith Cu yielded higher value than zeolite-4A filled with Ag
Advances in Materials Science and Engineering 7
038
044
056
048052
008 009
019
013
019
Z4A Cu4Z4A Cu6Z4A Ag4Z4A Ag15Z4A
COP
000
010
020
030
040
050
060
COP
Wmax
Figure 10 Effect of zeolite type COP
This is because of the ion exchange between sodium ion(Na+) and cations of metal Copper ion was divalent cationthat could balance framework negative charge for 2 sitesHowever silver ionwasmonovalent cation that could balanceonly 1 site Two sites exchange (copper ion) resulted in lowernumber of exchangeable cations in zeolite structure higherpore volume and higher adsorption capacity Consideringthe size of atoms and ions it was found that silver ion (Ag+126 pm) is not different than silver atom (Ag 144 pm) whilethe size of the copper ion (Cu2+ 72 pm) is more differentthan copper atom (Cu 128 pm) The BET method of bothpure and metal loaded zeolite-4A samples is given in Table 2The increase in the loading of silver in zeolite-4A causesa decrease in the surface area due to obstruction of activesite of zeolite by large size of silver ion The decrease inthe pore volume by silver loading is in agreement with thesurface area measurements An increase in the surface areawas observed for copper loading when the copper amountsexceeded a certain critical value This increase in the surfacearea is suspected to be due to the phase separation of thecopper precursors after a critical loading The data alsoshows that Cu2+ is twice smaller than Ag+ So this affectedthe maximum adsorption of water by Cu6Z4A in highervolume compared to Ag15Z4A
4 Conclusions
We were able to use Thai clay to synthesize zeolite-4A byconverting it into metakaolinite via calcination at 873K andactivation by 35molL NaOH with more than 70 yields
In testing performance of COP systems we found thatthe temperature of the adsorber and condenser affected theCOPThat is in the adsorption step as adsorber temperatureincreased adsorption was reduced decreasing COP of thesystem In desorption when adsorber temperature increaseda higher mass of refrigerant was desorbed leading to bettersystem COP
Moreover zeolite filled with copper and silver enhancessystemCOP relative to pure zeolite because copper and silverincrease pore volume which empowers water adsorptionwhich results in fast and efficient desorption of water andleads to better system COP
Nomenclature
119862119901119897 Specific heat of adsorbate in liquid phase119862119901119908 Specific heat of adsorbate in adsorbed phase
119862119901119911 Specific heat of adsorbent
COP Coefficient of PerformanceΔ119867 Heat of desorption of adsorbateK Kelvin temperature scale119871 Heat of evaporation of adsorbate119898119911 Mass of adsorbent119876des Heat of desorption119876119890 Heat of produced cooling system119876119904119889 The sensible heat of adsorbent1198791198861 Initial adsorption temperature1198791198862 Final adsorption temperature119879119888 Inside condenser temperature119879119890 Inside evaporator temperature1198791198921 Initial desorption temperature1198791198922 Final desorption temperature119882max Maximum adsorption performance119882min Minimum adsorption performance120603 Average adsorption performance
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors thank Miss Warunee Yuthphan MineralResources Development Co Ltd for providing Ranong claythe Department of Chemistry King Mongkutrsquos Institute ofTechnology Ladkrabang for acquiring the XDF XRD andSEM data and Energy Policy and Planning Office Ministryof Energy Royal Thai Government for financial support
References
[1] D C Wang Y H Li D Li Y Z Xia and J P Zhang ldquoAreview on adsorption refrigeration technology and adsorptiondeterioration in physical adsorption systemsrdquo Renewable andSustainable Energy Reviews vol 14 no 1 pp 344ndash353 2010
[2] L W Wang R Z Wang and R G Oliveira ldquoA review onadsorption working pairs for refrigerationrdquo Renewable andSustainable Energy Reviews vol 13 no 3 pp 518ndash534 2009
[3] E E Anyanwu ldquoReview of solid adsorption solar refrigerationII an overview of the principles and theoryrdquo Energy Conversionand Management vol 45 no 7-8 pp 1279ndash1295 2004
[4] K C Chan C Y H Chao G N Sze-To and K S HuildquoPerformance predictions for a new zeolite 13XCaCl
2com-
posite adsorbent for adsorption cooling systemsrdquo InternationalJournal of Heat and Mass Transfer vol 55 no 11-12 pp 3214ndash3224 2012
8 Advances in Materials Science and Engineering
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
(i) 65 zeolite + 35metallic foam and (ii) 70 zeolite + 30natural expanded graphiteThe latter combination performedbetter [7] A similar performance was noted by Hu et al whofound that if the evaporation temperature is set to 269K therequired condition temperature should not exceed 303K [8]
Biloe et al used polyvinyl alcohol mixed with polyethy-lene glycol as bonding agent and graphite mixed with acti-vated carbon as adsorbent in a methane adsorption systemThey found that adsorption of methane was improved dueto the increased ratio of graphite [9] Restuccia et al [10]used 20 bentonite as bonding agent for zeolite Y particlesto enhance heat transfer in a heat exchange tube They foundthat bentonite had no effect on adsorption of zeolite Y andimproved heat transfer rate Zhao et al [11] investigatedzeolite 13X by loading sodium silicate in different portionsfor an adsorption system They found that an increased levelof sodium silicate led to increased heat transfer In additionHu et al developed an adsorption system using heat froman exhaust pipe with an adsorption device based on zeolitemixed with aluminium They found that zeolite-aluminiumfoam augmented the COP of an adsorption system comparedto zeolite alone [8]
Our present work investigated experimentally theadsorption capacity of water on zeolite-4A from Thai claywith silver and copper loading to determine the COP foradsorption and desorption processes
2 Materials and Methods
21 Raw Material Clay was supplied by Mineral ResourcesDevelopment Co Ltd sourced from Ranong Thailand(9∘5710158404310158401015840N 98∘3810158402010158401015840E) Laboratory Reagent (LR) gradesodium hydroxide was used for ion exchange procedure
22 Preparation of Zeolite Type-4A Zeolite-4A was syn-thesized from clay in two processes metakaolinisation andzeolitisation following Chandrasekhar et al [12]
Metakaolinisation heats the clay to a high tempera-ture until it transforms its crystal structure and turns intometakaolinite Zeolitisation drives Na+ ions into the crystalstructure to form zeolite-4A
For our experiments we performed synthesis by calcina-tion at 873K for 3 h until the clay turned into metakaoliniteThen 05 kg of metakaolinite was mixed with 25 L of 35Msodium hydroxide at 363K for 3 h to insert Na+ ions intothe metakaolinite structure The slurry of metakaolinite wasthen filtered and washed several times with distilled water toremove excess unreacted NaOH Then it was filtered againand dried in an air oven at 373K overnight We had studiedthe maximum yield (70) in previous work [13] Thereforethe preparation was done in the same condition before metalloading in this work The chemical reaction in this step is
2Al2Si2O5(OH)4997888rarr 2Al
2Si2O7+ 4H2O (1)
6Al2Si2O7+ 12NaOH
997888rarr Na12(AlO2)12(SiO2)12sdot 27H2O + 6H
2O
(2)
23 Preparation of Metal-Impregnated Zeolite-4A 05 kg ofzeolite-4A was mixed with 25 L of silver nitrate or coppersulfate solution at the desired concentration at 323K for30mins After that the mixture was dried at 343K for 4 daysFinally the calcined material was heated at 573K for 2 h
24 Characterization of RawMaterial and Zeolite-4A Chem-ical compositions of raw kaolin samples were determinedby X-ray fluorescence spectroscopy using a Bruker AXS SRS3400
The crystallinity of the inorganic components was ana-lyzed by XRD (Bruker D8 Germany) with Cu-K
120572radiation
used to record the diffraction spectra The tube voltageand current were 30 kV and 30mA The area of 8 strongdiffraction peaks of the sample was compared to the patternof standard zeolite which was set to be 100
The morphology of samples was observed using a Scan-ning Electron Microscope (Leo 1455 VP UK) using anaccelerating voltage of 15 kV
Brunauer-Emmett-Teller (BET) analysis used aMicrome-ritics surface analyzer (ASAP2020 USA) to determine thespecific surface area of the zeolite and the pore size wascalculated by the Barrett-Joyner-Halenda (BJH) method viadesorption-adsorption of nitrogen gas at 78K
25 Basic Adsorption Cycle A complete adsorption coolingcycle that consists of adsorption (evaporation + cooling)and desorption (condensation + heating) can be explainedwith the help of the Clapeyron diagram in Figure 1 Theidealized cycle begins at point 1 where the maximum amountof refrigerant is adsorbedThe adsorbent is at low temperatureand low pressure at point 1 Along line 1-2 the adsorbentis heated and desorbs refrigerant vapor isosterically Thisstep is isosteric because there will be no refrigerant flowuntil the pressure inside the adsorbent bed becomes equalto or greater than the pressure of the condenser and theamount of desorbed refrigerant is small relative to the totalamount adsorbed Continued heating (line 2-3) desorbsmorerefrigerant forcing it to the condenser until state 3 is attainedat which desorption ceases This second step is isobaricdesorption Then the hot adsorbent is cooled isostericallycausing adsorption and depressurization (line 3-4)When thepressure drops below 119875ev refrigerant in the evaporator startsto boil and flows to the adsorbent bed producing the coolingeffect Cooling of the adsorbent continues until the bed issaturated with refrigerant completing the cycle This process(line 4-1) is isobaric adsorption
The COP of the system can be calculated as reportedin Cacciola and Restuccia [14] As seen from Figure 1 thethermodynamic cycle consists of 4 processes
4 rarr 1 isobaric adsorption (heat of adsorption +sensible cooling)
Advances in Materials Science and Engineering 3
P
Pcond
Pev
Desorption
Resorption
1
2 3
4
Isostericheating
Isostericcooling
Ta1Tg1Ta2 Tg2
T
Wmax Wmin
Figure 1 P-T-W diagram of the basic adsorption cycle [14]
In isosteric heating (1rarr 2) and isobaric desorption (2rarr3) heat is added to the adsorbent bedThe heat supplied to theadsorbent bed for its isosteric heating (1rarr 2) is
11987612= 119898119911(119862119901119911+ 119862119901119908119882max) (1198791198921 minus 1198791198862) (3)
where 119898119911is the mass of adsorbent in kg 119862
119901119911is the specific
heat of adsorbent in kJkg-K and 119862119901119908
is the specific heat ofadsorbate in the adsorbed phase in kJkg-K
The heat necessary for the desorption phase (2rarr 3) hastwo components
The useful refrigeration effect which is the energy thatmust be supplied to the evaporator 119876
119890 is calculated as the
latent heat of evaporation of the cycled adsorbate minus thesensible heat of the adsorbate that is entering the evaporatorat condensation temperature
119876119890= 119898119911(119882max minus119882min) [119871 minus 119862119901119897 (119879119888 minus 119879119890)] (7)
where119862119901119897is the specific heat of adsorbate in liquid phase and
119871 is the heat of evaporation of adsorbate in kJkgFrom the previous equations the COP for cooling opera-
tion can be calculated as the ratio of useful refrigeration effectproduced and heat input to the adsorbent bed
COP =119876119890
11987612+ 11987623
(8)
Table 1 Chemical composition of clay at Ranong province
Component SiO2
Al2O3
SO3
K2O Fe
2O3
CuO weight 522 433 036 218 161 025
26 Experimental Setup Before starting the experiments thelaboratory was prepared according to the procedure givenby Cacciola and Restuccia [14] An overview of the rigcomponents is shown in Figure 2 A known mass of zeolitewas put into the adsorber The adsorber line was connectedto the evaporator and condenser line
System preparation steps before activating the systemare as follows
(1) Turn off every valve(2) Put 01 kg of zeolites into adsorber(3) Put 03 L of water into evaporator(4) Adjust vacuumpressure value of evaporator at 73 kPa(5) For adsorber and condenser adjust vacuum pressure
value at 87 kPa within 20mins
Desorption system tests are as follows
(1) Valve V1
opened slowly to allow the water vaporto flow into the adsorber for 30mins after whichthe system reaches thermodynamic equilibrium ofadsorption
(2) Turn off valve V1
(3) Then begin desorption process by generating heat foradsorber at the designated temperature
(4) After that turn on valves V2 V3 and V
4to allow the
water vapor into condenser which contains refriger-ant to condense vapor into liquid
(5) Collectively store it at evaporator for 30mins afterwhich the system reaches thermodynamic equilib-rium of desorption process
(6) All valves closed
Adsorption system testing valve V1opened slowly to
allow the water vapor to flow into the adsorber for 30minsafter which the system reaches thermodynamic equilibriumof adsorption process and turn off valve V
1
For all steps temperature was recorded by a data loggerThe total amount of water desorbed and adsorbed by zeolitewas read from the balance
3 Results and Discussions
31 Properties of Zeolite-4A The chemical composition ofclay from Ranong province in Thailand is in Table 1 Themain components of the clay samples were oxides of Si andAl but they contain sulfur potassium iron and copperimpurities Therefore zeolite-4A prepared from this clay isalways contaminated with these elements
The XRD patterns of the solid samples are shown andcompared to the pattern of standard zeolite in Figure 3 it can
4 Advances in Materials Science and Engineering
Adsorber
Condenser
Evaporator
V1
V2
V3
V4
Figure 2 Photograph of adsorption refrigeration system
Ranong kaolinSyn Z4AStd Z4A
0100200300400500600700800900
1000
5 10 15 20 25 30 35 40 45 50 55 6002Φ
Figure 3 X-ray diffraction patterns of clay and zeolite-4A
be seen that synthesized clay for zeolite-4A (Z4A) compriseskaolinite as main element and when it was heated at 773Kkaolinite became more crystalized showing a higher peakvalue because organic compounds had evaporated at 773Kand made kaolinite purer Also peak was found along 2axes at the same position as a zeolite-4A reference so weconcluded that clay was transformed to zeolite-4A
When examining microstructure attributes of clay usingScanning Electron Microscope (SEM) we found crystallinestructures arranged in layers see Figure 4(a) Figure 4(b)shows the prepared zeolite-4A which has crystalline angles
Table 2 Specific surface area total pore volume and average porediameter
that corresponded with sharp peaks in the XRD spectrumhaving the crystalline attributes of zeolite-4A
Figure 5 shows the zeolite-4A surface filled with copper(Cu6Z4A) (a) and silver (Ag15Z4A) (b) at 5000xmagnification It can be clearly seen that silver particles werethinly dispersed on the zeolite-4A surface whereas copperparticles aggregated into larger clumps on the surface (a)
Synthesized zeolite-4A was analyzed for quality of poros-ity using adsorption of nitrogen at 78K with Micromeriticschemisorption analyzer model ASAP2020 Pore surface areawas determined using the Brunauer-Emmett-Teller (BET)formula to total pore volume at 119875119875
119900= 097 and average
pore diameter calculated by equation (4 times total pore vol-ume)surface
Figure 6 shows the N2adsorption isotherm of zeolite-4A
at 78Kwhich indicated that the adsorption isothermwas sim-ilar to type IV in the nomenclature IUPAC for mesoporousmaterials Table 2 shows that for synthesized zeolite-4Awhen sodium ions (Na+) were replaced with copper (Cu2+)or silver (Ag+) ions the total pore volume and pore diameterincreased relatively to pure zeolite-4A Cu6Z4A showedthe highest value for surface area (182m2g) total porevolume (00428mLg) and average pore diameter (939 nm)IUPAC defines three types of pore diameter micropore(lt2 nm) mesopore (2ndash50 nm) and macropore (gt50 nm)Our analysis showed that all synthesized zeolite-4A sampleswere mesopore and this indicates that this zeolite-4A couldadsorb water with diameter 028 nm and average poresmaller than the diameter of all zeolites
32 Adsorption and Desorption Behavior Testing adsorptionunder vacuum conditions involved two processes adsorp-tion and desorption Five samples of synthesized adsorbentwere tested Z4A Cu4Z4A Cu6Z4A Ag4Z4A andAg15Z4A Maximum adsorption (119882max) and minimumadsorption (119882min) of zeolite-4A are shown in Figures 7ndash9
Physical adsorption depended on pore diameter andpore volume Generally good adsorption occurred at lowtemperature due to the exothermic process So when the tem-perature was increased the degree of adsorption decreasedFigure 7 shows the water adsorptionmass during adsorptionwe found that when the adsorber temperature increasedadsorption performance ofwater decreased from008 at 315Kto 003 at 318 K and the COP reduced correspondingly
During evaporation after providing heat to adsorber attemperatures from 393 to 478K for 30mins heat from
Advances in Materials Science and Engineering 5
(a) (b)
Figure 4 SEM photograph of clay (a) and zeolite-4A (b)
Figure 7 Effect of adsorption temperature on119882max and COP
007004
002
018
035038
393 435 478
COP
000
005
010
015
020
025
030
035
040
COP
K
Wmin
Figure 8 Effect of desorption temperature on119882min and COP
adsorber was transferred to zeolite-4A until it reached thestable stage After that vapor was expelled from the zeolite-4A and shifted to condenser vapor condensed and collectedin the evaporator
From Figure 8 we see the lowest adsorption weightfor working pairs (zeolite-4A and water) it was found thatheat must be increasingly supplied for adsorber at 478K togain the maximum evaporation from zeolite Kinetic energyof vapor held unequal value when temperature changedWhen the temperature increased vapor mobility increasedso better desorption performance was observed Water wasevaporated faster from adsorber during desorption and ahigher water volume was adsorbed in the absorption step
001 002 002
042
038 038
285 289 294
COP
000
005
010
015
020
025
030
035
040
045
COP
K
Wmin
Figure 9 Effect of condenser temperature on119882min and COP
Figure 9 shows that the water mass adsorbed duringthe exothermic process was little effected by temperaturebetween 285 and 294K Water molecules adsorbed in thezeolite-4A pores could be condensed to liquid at a tem-perature higher than boiling point in the process calledcapillary condensation When the condensation temperatureincreased the saturated vapor pressure within the condenserwas also increased blocking (or hindering) transfer of vaporinto the condenser This led to ineffective desorption and themass of vapor being desorbed was also reducedThese resultswere based on a small-scale experiment so the adsorbedwater mass and COP showed little significant differencebetween 285 and 294K therefore to save energy in vaporcondensation step the condensation temperature was set tomatch the very slightly larger COP at 294K
33 COP of Adsorption Cooling System Investigating adsorp-tion cooling system using referential equation of Cacciolaand Restuccia [14] could determine the COP of the systemThe parameters obtained from maximum and minimumadsorption were adsorber at 305K during adsorption andadsorber at 478K during desorption
Figure 10 shows that copper and silver added to thezeolite-4A significantly affected systemCOPbecause a highermass of water was adsorbed by copper or silver filled zeolite-4A compared to pure zeolite-4A This maximum adsorption(119882max) was increased because size and volume of poreswere also increased However minimum adsorption (119882min)showed no significant difference because the increase ofaverage pore diameter allowed vapor to be evaporated easilyfrom the pores when receiving heat at temperature higherthan the boiling point Our results showed that COPs were056 for Cu6Z4A and 052 for Ag15Z4A whereas COPof Z4A was only 038 showing that adding copper and silvereffectively increased the systemCOP COP of zeolite-4A filledwith Cu yielded higher value than zeolite-4A filled with Ag
Advances in Materials Science and Engineering 7
038
044
056
048052
008 009
019
013
019
Z4A Cu4Z4A Cu6Z4A Ag4Z4A Ag15Z4A
COP
000
010
020
030
040
050
060
COP
Wmax
Figure 10 Effect of zeolite type COP
This is because of the ion exchange between sodium ion(Na+) and cations of metal Copper ion was divalent cationthat could balance framework negative charge for 2 sitesHowever silver ionwasmonovalent cation that could balanceonly 1 site Two sites exchange (copper ion) resulted in lowernumber of exchangeable cations in zeolite structure higherpore volume and higher adsorption capacity Consideringthe size of atoms and ions it was found that silver ion (Ag+126 pm) is not different than silver atom (Ag 144 pm) whilethe size of the copper ion (Cu2+ 72 pm) is more differentthan copper atom (Cu 128 pm) The BET method of bothpure and metal loaded zeolite-4A samples is given in Table 2The increase in the loading of silver in zeolite-4A causesa decrease in the surface area due to obstruction of activesite of zeolite by large size of silver ion The decrease inthe pore volume by silver loading is in agreement with thesurface area measurements An increase in the surface areawas observed for copper loading when the copper amountsexceeded a certain critical value This increase in the surfacearea is suspected to be due to the phase separation of thecopper precursors after a critical loading The data alsoshows that Cu2+ is twice smaller than Ag+ So this affectedthe maximum adsorption of water by Cu6Z4A in highervolume compared to Ag15Z4A
4 Conclusions
We were able to use Thai clay to synthesize zeolite-4A byconverting it into metakaolinite via calcination at 873K andactivation by 35molL NaOH with more than 70 yields
In testing performance of COP systems we found thatthe temperature of the adsorber and condenser affected theCOPThat is in the adsorption step as adsorber temperatureincreased adsorption was reduced decreasing COP of thesystem In desorption when adsorber temperature increaseda higher mass of refrigerant was desorbed leading to bettersystem COP
Moreover zeolite filled with copper and silver enhancessystemCOP relative to pure zeolite because copper and silverincrease pore volume which empowers water adsorptionwhich results in fast and efficient desorption of water andleads to better system COP
Nomenclature
119862119901119897 Specific heat of adsorbate in liquid phase119862119901119908 Specific heat of adsorbate in adsorbed phase
119862119901119911 Specific heat of adsorbent
COP Coefficient of PerformanceΔ119867 Heat of desorption of adsorbateK Kelvin temperature scale119871 Heat of evaporation of adsorbate119898119911 Mass of adsorbent119876des Heat of desorption119876119890 Heat of produced cooling system119876119904119889 The sensible heat of adsorbent1198791198861 Initial adsorption temperature1198791198862 Final adsorption temperature119879119888 Inside condenser temperature119879119890 Inside evaporator temperature1198791198921 Initial desorption temperature1198791198922 Final desorption temperature119882max Maximum adsorption performance119882min Minimum adsorption performance120603 Average adsorption performance
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors thank Miss Warunee Yuthphan MineralResources Development Co Ltd for providing Ranong claythe Department of Chemistry King Mongkutrsquos Institute ofTechnology Ladkrabang for acquiring the XDF XRD andSEM data and Energy Policy and Planning Office Ministryof Energy Royal Thai Government for financial support
References
[1] D C Wang Y H Li D Li Y Z Xia and J P Zhang ldquoAreview on adsorption refrigeration technology and adsorptiondeterioration in physical adsorption systemsrdquo Renewable andSustainable Energy Reviews vol 14 no 1 pp 344ndash353 2010
[2] L W Wang R Z Wang and R G Oliveira ldquoA review onadsorption working pairs for refrigerationrdquo Renewable andSustainable Energy Reviews vol 13 no 3 pp 518ndash534 2009
[3] E E Anyanwu ldquoReview of solid adsorption solar refrigerationII an overview of the principles and theoryrdquo Energy Conversionand Management vol 45 no 7-8 pp 1279ndash1295 2004
[4] K C Chan C Y H Chao G N Sze-To and K S HuildquoPerformance predictions for a new zeolite 13XCaCl
2com-
posite adsorbent for adsorption cooling systemsrdquo InternationalJournal of Heat and Mass Transfer vol 55 no 11-12 pp 3214ndash3224 2012
8 Advances in Materials Science and Engineering
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
Figure 1 P-T-W diagram of the basic adsorption cycle [14]
In isosteric heating (1rarr 2) and isobaric desorption (2rarr3) heat is added to the adsorbent bedThe heat supplied to theadsorbent bed for its isosteric heating (1rarr 2) is
11987612= 119898119911(119862119901119911+ 119862119901119908119882max) (1198791198921 minus 1198791198862) (3)
where 119898119911is the mass of adsorbent in kg 119862
119901119911is the specific
heat of adsorbent in kJkg-K and 119862119901119908
is the specific heat ofadsorbate in the adsorbed phase in kJkg-K
The heat necessary for the desorption phase (2rarr 3) hastwo components
The useful refrigeration effect which is the energy thatmust be supplied to the evaporator 119876
119890 is calculated as the
latent heat of evaporation of the cycled adsorbate minus thesensible heat of the adsorbate that is entering the evaporatorat condensation temperature
119876119890= 119898119911(119882max minus119882min) [119871 minus 119862119901119897 (119879119888 minus 119879119890)] (7)
where119862119901119897is the specific heat of adsorbate in liquid phase and
119871 is the heat of evaporation of adsorbate in kJkgFrom the previous equations the COP for cooling opera-
tion can be calculated as the ratio of useful refrigeration effectproduced and heat input to the adsorbent bed
COP =119876119890
11987612+ 11987623
(8)
Table 1 Chemical composition of clay at Ranong province
Component SiO2
Al2O3
SO3
K2O Fe
2O3
CuO weight 522 433 036 218 161 025
26 Experimental Setup Before starting the experiments thelaboratory was prepared according to the procedure givenby Cacciola and Restuccia [14] An overview of the rigcomponents is shown in Figure 2 A known mass of zeolitewas put into the adsorber The adsorber line was connectedto the evaporator and condenser line
System preparation steps before activating the systemare as follows
(1) Turn off every valve(2) Put 01 kg of zeolites into adsorber(3) Put 03 L of water into evaporator(4) Adjust vacuumpressure value of evaporator at 73 kPa(5) For adsorber and condenser adjust vacuum pressure
value at 87 kPa within 20mins
Desorption system tests are as follows
(1) Valve V1
opened slowly to allow the water vaporto flow into the adsorber for 30mins after whichthe system reaches thermodynamic equilibrium ofadsorption
(2) Turn off valve V1
(3) Then begin desorption process by generating heat foradsorber at the designated temperature
(4) After that turn on valves V2 V3 and V
4to allow the
water vapor into condenser which contains refriger-ant to condense vapor into liquid
(5) Collectively store it at evaporator for 30mins afterwhich the system reaches thermodynamic equilib-rium of desorption process
(6) All valves closed
Adsorption system testing valve V1opened slowly to
allow the water vapor to flow into the adsorber for 30minsafter which the system reaches thermodynamic equilibriumof adsorption process and turn off valve V
1
For all steps temperature was recorded by a data loggerThe total amount of water desorbed and adsorbed by zeolitewas read from the balance
3 Results and Discussions
31 Properties of Zeolite-4A The chemical composition ofclay from Ranong province in Thailand is in Table 1 Themain components of the clay samples were oxides of Si andAl but they contain sulfur potassium iron and copperimpurities Therefore zeolite-4A prepared from this clay isalways contaminated with these elements
The XRD patterns of the solid samples are shown andcompared to the pattern of standard zeolite in Figure 3 it can
4 Advances in Materials Science and Engineering
Adsorber
Condenser
Evaporator
V1
V2
V3
V4
Figure 2 Photograph of adsorption refrigeration system
Ranong kaolinSyn Z4AStd Z4A
0100200300400500600700800900
1000
5 10 15 20 25 30 35 40 45 50 55 6002Φ
Figure 3 X-ray diffraction patterns of clay and zeolite-4A
be seen that synthesized clay for zeolite-4A (Z4A) compriseskaolinite as main element and when it was heated at 773Kkaolinite became more crystalized showing a higher peakvalue because organic compounds had evaporated at 773Kand made kaolinite purer Also peak was found along 2axes at the same position as a zeolite-4A reference so weconcluded that clay was transformed to zeolite-4A
When examining microstructure attributes of clay usingScanning Electron Microscope (SEM) we found crystallinestructures arranged in layers see Figure 4(a) Figure 4(b)shows the prepared zeolite-4A which has crystalline angles
Table 2 Specific surface area total pore volume and average porediameter
that corresponded with sharp peaks in the XRD spectrumhaving the crystalline attributes of zeolite-4A
Figure 5 shows the zeolite-4A surface filled with copper(Cu6Z4A) (a) and silver (Ag15Z4A) (b) at 5000xmagnification It can be clearly seen that silver particles werethinly dispersed on the zeolite-4A surface whereas copperparticles aggregated into larger clumps on the surface (a)
Synthesized zeolite-4A was analyzed for quality of poros-ity using adsorption of nitrogen at 78K with Micromeriticschemisorption analyzer model ASAP2020 Pore surface areawas determined using the Brunauer-Emmett-Teller (BET)formula to total pore volume at 119875119875
119900= 097 and average
pore diameter calculated by equation (4 times total pore vol-ume)surface
Figure 6 shows the N2adsorption isotherm of zeolite-4A
at 78Kwhich indicated that the adsorption isothermwas sim-ilar to type IV in the nomenclature IUPAC for mesoporousmaterials Table 2 shows that for synthesized zeolite-4Awhen sodium ions (Na+) were replaced with copper (Cu2+)or silver (Ag+) ions the total pore volume and pore diameterincreased relatively to pure zeolite-4A Cu6Z4A showedthe highest value for surface area (182m2g) total porevolume (00428mLg) and average pore diameter (939 nm)IUPAC defines three types of pore diameter micropore(lt2 nm) mesopore (2ndash50 nm) and macropore (gt50 nm)Our analysis showed that all synthesized zeolite-4A sampleswere mesopore and this indicates that this zeolite-4A couldadsorb water with diameter 028 nm and average poresmaller than the diameter of all zeolites
32 Adsorption and Desorption Behavior Testing adsorptionunder vacuum conditions involved two processes adsorp-tion and desorption Five samples of synthesized adsorbentwere tested Z4A Cu4Z4A Cu6Z4A Ag4Z4A andAg15Z4A Maximum adsorption (119882max) and minimumadsorption (119882min) of zeolite-4A are shown in Figures 7ndash9
Physical adsorption depended on pore diameter andpore volume Generally good adsorption occurred at lowtemperature due to the exothermic process So when the tem-perature was increased the degree of adsorption decreasedFigure 7 shows the water adsorptionmass during adsorptionwe found that when the adsorber temperature increasedadsorption performance ofwater decreased from008 at 315Kto 003 at 318 K and the COP reduced correspondingly
During evaporation after providing heat to adsorber attemperatures from 393 to 478K for 30mins heat from
Advances in Materials Science and Engineering 5
(a) (b)
Figure 4 SEM photograph of clay (a) and zeolite-4A (b)
Figure 7 Effect of adsorption temperature on119882max and COP
007004
002
018
035038
393 435 478
COP
000
005
010
015
020
025
030
035
040
COP
K
Wmin
Figure 8 Effect of desorption temperature on119882min and COP
adsorber was transferred to zeolite-4A until it reached thestable stage After that vapor was expelled from the zeolite-4A and shifted to condenser vapor condensed and collectedin the evaporator
From Figure 8 we see the lowest adsorption weightfor working pairs (zeolite-4A and water) it was found thatheat must be increasingly supplied for adsorber at 478K togain the maximum evaporation from zeolite Kinetic energyof vapor held unequal value when temperature changedWhen the temperature increased vapor mobility increasedso better desorption performance was observed Water wasevaporated faster from adsorber during desorption and ahigher water volume was adsorbed in the absorption step
001 002 002
042
038 038
285 289 294
COP
000
005
010
015
020
025
030
035
040
045
COP
K
Wmin
Figure 9 Effect of condenser temperature on119882min and COP
Figure 9 shows that the water mass adsorbed duringthe exothermic process was little effected by temperaturebetween 285 and 294K Water molecules adsorbed in thezeolite-4A pores could be condensed to liquid at a tem-perature higher than boiling point in the process calledcapillary condensation When the condensation temperatureincreased the saturated vapor pressure within the condenserwas also increased blocking (or hindering) transfer of vaporinto the condenser This led to ineffective desorption and themass of vapor being desorbed was also reducedThese resultswere based on a small-scale experiment so the adsorbedwater mass and COP showed little significant differencebetween 285 and 294K therefore to save energy in vaporcondensation step the condensation temperature was set tomatch the very slightly larger COP at 294K
33 COP of Adsorption Cooling System Investigating adsorp-tion cooling system using referential equation of Cacciolaand Restuccia [14] could determine the COP of the systemThe parameters obtained from maximum and minimumadsorption were adsorber at 305K during adsorption andadsorber at 478K during desorption
Figure 10 shows that copper and silver added to thezeolite-4A significantly affected systemCOPbecause a highermass of water was adsorbed by copper or silver filled zeolite-4A compared to pure zeolite-4A This maximum adsorption(119882max) was increased because size and volume of poreswere also increased However minimum adsorption (119882min)showed no significant difference because the increase ofaverage pore diameter allowed vapor to be evaporated easilyfrom the pores when receiving heat at temperature higherthan the boiling point Our results showed that COPs were056 for Cu6Z4A and 052 for Ag15Z4A whereas COPof Z4A was only 038 showing that adding copper and silvereffectively increased the systemCOP COP of zeolite-4A filledwith Cu yielded higher value than zeolite-4A filled with Ag
Advances in Materials Science and Engineering 7
038
044
056
048052
008 009
019
013
019
Z4A Cu4Z4A Cu6Z4A Ag4Z4A Ag15Z4A
COP
000
010
020
030
040
050
060
COP
Wmax
Figure 10 Effect of zeolite type COP
This is because of the ion exchange between sodium ion(Na+) and cations of metal Copper ion was divalent cationthat could balance framework negative charge for 2 sitesHowever silver ionwasmonovalent cation that could balanceonly 1 site Two sites exchange (copper ion) resulted in lowernumber of exchangeable cations in zeolite structure higherpore volume and higher adsorption capacity Consideringthe size of atoms and ions it was found that silver ion (Ag+126 pm) is not different than silver atom (Ag 144 pm) whilethe size of the copper ion (Cu2+ 72 pm) is more differentthan copper atom (Cu 128 pm) The BET method of bothpure and metal loaded zeolite-4A samples is given in Table 2The increase in the loading of silver in zeolite-4A causesa decrease in the surface area due to obstruction of activesite of zeolite by large size of silver ion The decrease inthe pore volume by silver loading is in agreement with thesurface area measurements An increase in the surface areawas observed for copper loading when the copper amountsexceeded a certain critical value This increase in the surfacearea is suspected to be due to the phase separation of thecopper precursors after a critical loading The data alsoshows that Cu2+ is twice smaller than Ag+ So this affectedthe maximum adsorption of water by Cu6Z4A in highervolume compared to Ag15Z4A
4 Conclusions
We were able to use Thai clay to synthesize zeolite-4A byconverting it into metakaolinite via calcination at 873K andactivation by 35molL NaOH with more than 70 yields
In testing performance of COP systems we found thatthe temperature of the adsorber and condenser affected theCOPThat is in the adsorption step as adsorber temperatureincreased adsorption was reduced decreasing COP of thesystem In desorption when adsorber temperature increaseda higher mass of refrigerant was desorbed leading to bettersystem COP
Moreover zeolite filled with copper and silver enhancessystemCOP relative to pure zeolite because copper and silverincrease pore volume which empowers water adsorptionwhich results in fast and efficient desorption of water andleads to better system COP
Nomenclature
119862119901119897 Specific heat of adsorbate in liquid phase119862119901119908 Specific heat of adsorbate in adsorbed phase
119862119901119911 Specific heat of adsorbent
COP Coefficient of PerformanceΔ119867 Heat of desorption of adsorbateK Kelvin temperature scale119871 Heat of evaporation of adsorbate119898119911 Mass of adsorbent119876des Heat of desorption119876119890 Heat of produced cooling system119876119904119889 The sensible heat of adsorbent1198791198861 Initial adsorption temperature1198791198862 Final adsorption temperature119879119888 Inside condenser temperature119879119890 Inside evaporator temperature1198791198921 Initial desorption temperature1198791198922 Final desorption temperature119882max Maximum adsorption performance119882min Minimum adsorption performance120603 Average adsorption performance
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors thank Miss Warunee Yuthphan MineralResources Development Co Ltd for providing Ranong claythe Department of Chemistry King Mongkutrsquos Institute ofTechnology Ladkrabang for acquiring the XDF XRD andSEM data and Energy Policy and Planning Office Ministryof Energy Royal Thai Government for financial support
References
[1] D C Wang Y H Li D Li Y Z Xia and J P Zhang ldquoAreview on adsorption refrigeration technology and adsorptiondeterioration in physical adsorption systemsrdquo Renewable andSustainable Energy Reviews vol 14 no 1 pp 344ndash353 2010
[2] L W Wang R Z Wang and R G Oliveira ldquoA review onadsorption working pairs for refrigerationrdquo Renewable andSustainable Energy Reviews vol 13 no 3 pp 518ndash534 2009
[3] E E Anyanwu ldquoReview of solid adsorption solar refrigerationII an overview of the principles and theoryrdquo Energy Conversionand Management vol 45 no 7-8 pp 1279ndash1295 2004
[4] K C Chan C Y H Chao G N Sze-To and K S HuildquoPerformance predictions for a new zeolite 13XCaCl
2com-
posite adsorbent for adsorption cooling systemsrdquo InternationalJournal of Heat and Mass Transfer vol 55 no 11-12 pp 3214ndash3224 2012
8 Advances in Materials Science and Engineering
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
Figure 2 Photograph of adsorption refrigeration system
Ranong kaolinSyn Z4AStd Z4A
0100200300400500600700800900
1000
5 10 15 20 25 30 35 40 45 50 55 6002Φ
Figure 3 X-ray diffraction patterns of clay and zeolite-4A
be seen that synthesized clay for zeolite-4A (Z4A) compriseskaolinite as main element and when it was heated at 773Kkaolinite became more crystalized showing a higher peakvalue because organic compounds had evaporated at 773Kand made kaolinite purer Also peak was found along 2axes at the same position as a zeolite-4A reference so weconcluded that clay was transformed to zeolite-4A
When examining microstructure attributes of clay usingScanning Electron Microscope (SEM) we found crystallinestructures arranged in layers see Figure 4(a) Figure 4(b)shows the prepared zeolite-4A which has crystalline angles
Table 2 Specific surface area total pore volume and average porediameter
that corresponded with sharp peaks in the XRD spectrumhaving the crystalline attributes of zeolite-4A
Figure 5 shows the zeolite-4A surface filled with copper(Cu6Z4A) (a) and silver (Ag15Z4A) (b) at 5000xmagnification It can be clearly seen that silver particles werethinly dispersed on the zeolite-4A surface whereas copperparticles aggregated into larger clumps on the surface (a)
Synthesized zeolite-4A was analyzed for quality of poros-ity using adsorption of nitrogen at 78K with Micromeriticschemisorption analyzer model ASAP2020 Pore surface areawas determined using the Brunauer-Emmett-Teller (BET)formula to total pore volume at 119875119875
119900= 097 and average
pore diameter calculated by equation (4 times total pore vol-ume)surface
Figure 6 shows the N2adsorption isotherm of zeolite-4A
at 78Kwhich indicated that the adsorption isothermwas sim-ilar to type IV in the nomenclature IUPAC for mesoporousmaterials Table 2 shows that for synthesized zeolite-4Awhen sodium ions (Na+) were replaced with copper (Cu2+)or silver (Ag+) ions the total pore volume and pore diameterincreased relatively to pure zeolite-4A Cu6Z4A showedthe highest value for surface area (182m2g) total porevolume (00428mLg) and average pore diameter (939 nm)IUPAC defines three types of pore diameter micropore(lt2 nm) mesopore (2ndash50 nm) and macropore (gt50 nm)Our analysis showed that all synthesized zeolite-4A sampleswere mesopore and this indicates that this zeolite-4A couldadsorb water with diameter 028 nm and average poresmaller than the diameter of all zeolites
32 Adsorption and Desorption Behavior Testing adsorptionunder vacuum conditions involved two processes adsorp-tion and desorption Five samples of synthesized adsorbentwere tested Z4A Cu4Z4A Cu6Z4A Ag4Z4A andAg15Z4A Maximum adsorption (119882max) and minimumadsorption (119882min) of zeolite-4A are shown in Figures 7ndash9
Physical adsorption depended on pore diameter andpore volume Generally good adsorption occurred at lowtemperature due to the exothermic process So when the tem-perature was increased the degree of adsorption decreasedFigure 7 shows the water adsorptionmass during adsorptionwe found that when the adsorber temperature increasedadsorption performance ofwater decreased from008 at 315Kto 003 at 318 K and the COP reduced correspondingly
During evaporation after providing heat to adsorber attemperatures from 393 to 478K for 30mins heat from
Advances in Materials Science and Engineering 5
(a) (b)
Figure 4 SEM photograph of clay (a) and zeolite-4A (b)
Figure 7 Effect of adsorption temperature on119882max and COP
007004
002
018
035038
393 435 478
COP
000
005
010
015
020
025
030
035
040
COP
K
Wmin
Figure 8 Effect of desorption temperature on119882min and COP
adsorber was transferred to zeolite-4A until it reached thestable stage After that vapor was expelled from the zeolite-4A and shifted to condenser vapor condensed and collectedin the evaporator
From Figure 8 we see the lowest adsorption weightfor working pairs (zeolite-4A and water) it was found thatheat must be increasingly supplied for adsorber at 478K togain the maximum evaporation from zeolite Kinetic energyof vapor held unequal value when temperature changedWhen the temperature increased vapor mobility increasedso better desorption performance was observed Water wasevaporated faster from adsorber during desorption and ahigher water volume was adsorbed in the absorption step
001 002 002
042
038 038
285 289 294
COP
000
005
010
015
020
025
030
035
040
045
COP
K
Wmin
Figure 9 Effect of condenser temperature on119882min and COP
Figure 9 shows that the water mass adsorbed duringthe exothermic process was little effected by temperaturebetween 285 and 294K Water molecules adsorbed in thezeolite-4A pores could be condensed to liquid at a tem-perature higher than boiling point in the process calledcapillary condensation When the condensation temperatureincreased the saturated vapor pressure within the condenserwas also increased blocking (or hindering) transfer of vaporinto the condenser This led to ineffective desorption and themass of vapor being desorbed was also reducedThese resultswere based on a small-scale experiment so the adsorbedwater mass and COP showed little significant differencebetween 285 and 294K therefore to save energy in vaporcondensation step the condensation temperature was set tomatch the very slightly larger COP at 294K
33 COP of Adsorption Cooling System Investigating adsorp-tion cooling system using referential equation of Cacciolaand Restuccia [14] could determine the COP of the systemThe parameters obtained from maximum and minimumadsorption were adsorber at 305K during adsorption andadsorber at 478K during desorption
Figure 10 shows that copper and silver added to thezeolite-4A significantly affected systemCOPbecause a highermass of water was adsorbed by copper or silver filled zeolite-4A compared to pure zeolite-4A This maximum adsorption(119882max) was increased because size and volume of poreswere also increased However minimum adsorption (119882min)showed no significant difference because the increase ofaverage pore diameter allowed vapor to be evaporated easilyfrom the pores when receiving heat at temperature higherthan the boiling point Our results showed that COPs were056 for Cu6Z4A and 052 for Ag15Z4A whereas COPof Z4A was only 038 showing that adding copper and silvereffectively increased the systemCOP COP of zeolite-4A filledwith Cu yielded higher value than zeolite-4A filled with Ag
Advances in Materials Science and Engineering 7
038
044
056
048052
008 009
019
013
019
Z4A Cu4Z4A Cu6Z4A Ag4Z4A Ag15Z4A
COP
000
010
020
030
040
050
060
COP
Wmax
Figure 10 Effect of zeolite type COP
This is because of the ion exchange between sodium ion(Na+) and cations of metal Copper ion was divalent cationthat could balance framework negative charge for 2 sitesHowever silver ionwasmonovalent cation that could balanceonly 1 site Two sites exchange (copper ion) resulted in lowernumber of exchangeable cations in zeolite structure higherpore volume and higher adsorption capacity Consideringthe size of atoms and ions it was found that silver ion (Ag+126 pm) is not different than silver atom (Ag 144 pm) whilethe size of the copper ion (Cu2+ 72 pm) is more differentthan copper atom (Cu 128 pm) The BET method of bothpure and metal loaded zeolite-4A samples is given in Table 2The increase in the loading of silver in zeolite-4A causesa decrease in the surface area due to obstruction of activesite of zeolite by large size of silver ion The decrease inthe pore volume by silver loading is in agreement with thesurface area measurements An increase in the surface areawas observed for copper loading when the copper amountsexceeded a certain critical value This increase in the surfacearea is suspected to be due to the phase separation of thecopper precursors after a critical loading The data alsoshows that Cu2+ is twice smaller than Ag+ So this affectedthe maximum adsorption of water by Cu6Z4A in highervolume compared to Ag15Z4A
4 Conclusions
We were able to use Thai clay to synthesize zeolite-4A byconverting it into metakaolinite via calcination at 873K andactivation by 35molL NaOH with more than 70 yields
In testing performance of COP systems we found thatthe temperature of the adsorber and condenser affected theCOPThat is in the adsorption step as adsorber temperatureincreased adsorption was reduced decreasing COP of thesystem In desorption when adsorber temperature increaseda higher mass of refrigerant was desorbed leading to bettersystem COP
Moreover zeolite filled with copper and silver enhancessystemCOP relative to pure zeolite because copper and silverincrease pore volume which empowers water adsorptionwhich results in fast and efficient desorption of water andleads to better system COP
Nomenclature
119862119901119897 Specific heat of adsorbate in liquid phase119862119901119908 Specific heat of adsorbate in adsorbed phase
119862119901119911 Specific heat of adsorbent
COP Coefficient of PerformanceΔ119867 Heat of desorption of adsorbateK Kelvin temperature scale119871 Heat of evaporation of adsorbate119898119911 Mass of adsorbent119876des Heat of desorption119876119890 Heat of produced cooling system119876119904119889 The sensible heat of adsorbent1198791198861 Initial adsorption temperature1198791198862 Final adsorption temperature119879119888 Inside condenser temperature119879119890 Inside evaporator temperature1198791198921 Initial desorption temperature1198791198922 Final desorption temperature119882max Maximum adsorption performance119882min Minimum adsorption performance120603 Average adsorption performance
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors thank Miss Warunee Yuthphan MineralResources Development Co Ltd for providing Ranong claythe Department of Chemistry King Mongkutrsquos Institute ofTechnology Ladkrabang for acquiring the XDF XRD andSEM data and Energy Policy and Planning Office Ministryof Energy Royal Thai Government for financial support
References
[1] D C Wang Y H Li D Li Y Z Xia and J P Zhang ldquoAreview on adsorption refrigeration technology and adsorptiondeterioration in physical adsorption systemsrdquo Renewable andSustainable Energy Reviews vol 14 no 1 pp 344ndash353 2010
[2] L W Wang R Z Wang and R G Oliveira ldquoA review onadsorption working pairs for refrigerationrdquo Renewable andSustainable Energy Reviews vol 13 no 3 pp 518ndash534 2009
[3] E E Anyanwu ldquoReview of solid adsorption solar refrigerationII an overview of the principles and theoryrdquo Energy Conversionand Management vol 45 no 7-8 pp 1279ndash1295 2004
[4] K C Chan C Y H Chao G N Sze-To and K S HuildquoPerformance predictions for a new zeolite 13XCaCl
2com-
posite adsorbent for adsorption cooling systemsrdquo InternationalJournal of Heat and Mass Transfer vol 55 no 11-12 pp 3214ndash3224 2012
8 Advances in Materials Science and Engineering
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
Figure 7 Effect of adsorption temperature on119882max and COP
007004
002
018
035038
393 435 478
COP
000
005
010
015
020
025
030
035
040
COP
K
Wmin
Figure 8 Effect of desorption temperature on119882min and COP
adsorber was transferred to zeolite-4A until it reached thestable stage After that vapor was expelled from the zeolite-4A and shifted to condenser vapor condensed and collectedin the evaporator
From Figure 8 we see the lowest adsorption weightfor working pairs (zeolite-4A and water) it was found thatheat must be increasingly supplied for adsorber at 478K togain the maximum evaporation from zeolite Kinetic energyof vapor held unequal value when temperature changedWhen the temperature increased vapor mobility increasedso better desorption performance was observed Water wasevaporated faster from adsorber during desorption and ahigher water volume was adsorbed in the absorption step
001 002 002
042
038 038
285 289 294
COP
000
005
010
015
020
025
030
035
040
045
COP
K
Wmin
Figure 9 Effect of condenser temperature on119882min and COP
Figure 9 shows that the water mass adsorbed duringthe exothermic process was little effected by temperaturebetween 285 and 294K Water molecules adsorbed in thezeolite-4A pores could be condensed to liquid at a tem-perature higher than boiling point in the process calledcapillary condensation When the condensation temperatureincreased the saturated vapor pressure within the condenserwas also increased blocking (or hindering) transfer of vaporinto the condenser This led to ineffective desorption and themass of vapor being desorbed was also reducedThese resultswere based on a small-scale experiment so the adsorbedwater mass and COP showed little significant differencebetween 285 and 294K therefore to save energy in vaporcondensation step the condensation temperature was set tomatch the very slightly larger COP at 294K
33 COP of Adsorption Cooling System Investigating adsorp-tion cooling system using referential equation of Cacciolaand Restuccia [14] could determine the COP of the systemThe parameters obtained from maximum and minimumadsorption were adsorber at 305K during adsorption andadsorber at 478K during desorption
Figure 10 shows that copper and silver added to thezeolite-4A significantly affected systemCOPbecause a highermass of water was adsorbed by copper or silver filled zeolite-4A compared to pure zeolite-4A This maximum adsorption(119882max) was increased because size and volume of poreswere also increased However minimum adsorption (119882min)showed no significant difference because the increase ofaverage pore diameter allowed vapor to be evaporated easilyfrom the pores when receiving heat at temperature higherthan the boiling point Our results showed that COPs were056 for Cu6Z4A and 052 for Ag15Z4A whereas COPof Z4A was only 038 showing that adding copper and silvereffectively increased the systemCOP COP of zeolite-4A filledwith Cu yielded higher value than zeolite-4A filled with Ag
Advances in Materials Science and Engineering 7
038
044
056
048052
008 009
019
013
019
Z4A Cu4Z4A Cu6Z4A Ag4Z4A Ag15Z4A
COP
000
010
020
030
040
050
060
COP
Wmax
Figure 10 Effect of zeolite type COP
This is because of the ion exchange between sodium ion(Na+) and cations of metal Copper ion was divalent cationthat could balance framework negative charge for 2 sitesHowever silver ionwasmonovalent cation that could balanceonly 1 site Two sites exchange (copper ion) resulted in lowernumber of exchangeable cations in zeolite structure higherpore volume and higher adsorption capacity Consideringthe size of atoms and ions it was found that silver ion (Ag+126 pm) is not different than silver atom (Ag 144 pm) whilethe size of the copper ion (Cu2+ 72 pm) is more differentthan copper atom (Cu 128 pm) The BET method of bothpure and metal loaded zeolite-4A samples is given in Table 2The increase in the loading of silver in zeolite-4A causesa decrease in the surface area due to obstruction of activesite of zeolite by large size of silver ion The decrease inthe pore volume by silver loading is in agreement with thesurface area measurements An increase in the surface areawas observed for copper loading when the copper amountsexceeded a certain critical value This increase in the surfacearea is suspected to be due to the phase separation of thecopper precursors after a critical loading The data alsoshows that Cu2+ is twice smaller than Ag+ So this affectedthe maximum adsorption of water by Cu6Z4A in highervolume compared to Ag15Z4A
4 Conclusions
We were able to use Thai clay to synthesize zeolite-4A byconverting it into metakaolinite via calcination at 873K andactivation by 35molL NaOH with more than 70 yields
In testing performance of COP systems we found thatthe temperature of the adsorber and condenser affected theCOPThat is in the adsorption step as adsorber temperatureincreased adsorption was reduced decreasing COP of thesystem In desorption when adsorber temperature increaseda higher mass of refrigerant was desorbed leading to bettersystem COP
Moreover zeolite filled with copper and silver enhancessystemCOP relative to pure zeolite because copper and silverincrease pore volume which empowers water adsorptionwhich results in fast and efficient desorption of water andleads to better system COP
Nomenclature
119862119901119897 Specific heat of adsorbate in liquid phase119862119901119908 Specific heat of adsorbate in adsorbed phase
119862119901119911 Specific heat of adsorbent
COP Coefficient of PerformanceΔ119867 Heat of desorption of adsorbateK Kelvin temperature scale119871 Heat of evaporation of adsorbate119898119911 Mass of adsorbent119876des Heat of desorption119876119890 Heat of produced cooling system119876119904119889 The sensible heat of adsorbent1198791198861 Initial adsorption temperature1198791198862 Final adsorption temperature119879119888 Inside condenser temperature119879119890 Inside evaporator temperature1198791198921 Initial desorption temperature1198791198922 Final desorption temperature119882max Maximum adsorption performance119882min Minimum adsorption performance120603 Average adsorption performance
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors thank Miss Warunee Yuthphan MineralResources Development Co Ltd for providing Ranong claythe Department of Chemistry King Mongkutrsquos Institute ofTechnology Ladkrabang for acquiring the XDF XRD andSEM data and Energy Policy and Planning Office Ministryof Energy Royal Thai Government for financial support
References
[1] D C Wang Y H Li D Li Y Z Xia and J P Zhang ldquoAreview on adsorption refrigeration technology and adsorptiondeterioration in physical adsorption systemsrdquo Renewable andSustainable Energy Reviews vol 14 no 1 pp 344ndash353 2010
[2] L W Wang R Z Wang and R G Oliveira ldquoA review onadsorption working pairs for refrigerationrdquo Renewable andSustainable Energy Reviews vol 13 no 3 pp 518ndash534 2009
[3] E E Anyanwu ldquoReview of solid adsorption solar refrigerationII an overview of the principles and theoryrdquo Energy Conversionand Management vol 45 no 7-8 pp 1279ndash1295 2004
[4] K C Chan C Y H Chao G N Sze-To and K S HuildquoPerformance predictions for a new zeolite 13XCaCl
2com-
posite adsorbent for adsorption cooling systemsrdquo InternationalJournal of Heat and Mass Transfer vol 55 no 11-12 pp 3214ndash3224 2012
8 Advances in Materials Science and Engineering
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
Figure 7 Effect of adsorption temperature on119882max and COP
007004
002
018
035038
393 435 478
COP
000
005
010
015
020
025
030
035
040
COP
K
Wmin
Figure 8 Effect of desorption temperature on119882min and COP
adsorber was transferred to zeolite-4A until it reached thestable stage After that vapor was expelled from the zeolite-4A and shifted to condenser vapor condensed and collectedin the evaporator
From Figure 8 we see the lowest adsorption weightfor working pairs (zeolite-4A and water) it was found thatheat must be increasingly supplied for adsorber at 478K togain the maximum evaporation from zeolite Kinetic energyof vapor held unequal value when temperature changedWhen the temperature increased vapor mobility increasedso better desorption performance was observed Water wasevaporated faster from adsorber during desorption and ahigher water volume was adsorbed in the absorption step
001 002 002
042
038 038
285 289 294
COP
000
005
010
015
020
025
030
035
040
045
COP
K
Wmin
Figure 9 Effect of condenser temperature on119882min and COP
Figure 9 shows that the water mass adsorbed duringthe exothermic process was little effected by temperaturebetween 285 and 294K Water molecules adsorbed in thezeolite-4A pores could be condensed to liquid at a tem-perature higher than boiling point in the process calledcapillary condensation When the condensation temperatureincreased the saturated vapor pressure within the condenserwas also increased blocking (or hindering) transfer of vaporinto the condenser This led to ineffective desorption and themass of vapor being desorbed was also reducedThese resultswere based on a small-scale experiment so the adsorbedwater mass and COP showed little significant differencebetween 285 and 294K therefore to save energy in vaporcondensation step the condensation temperature was set tomatch the very slightly larger COP at 294K
33 COP of Adsorption Cooling System Investigating adsorp-tion cooling system using referential equation of Cacciolaand Restuccia [14] could determine the COP of the systemThe parameters obtained from maximum and minimumadsorption were adsorber at 305K during adsorption andadsorber at 478K during desorption
Figure 10 shows that copper and silver added to thezeolite-4A significantly affected systemCOPbecause a highermass of water was adsorbed by copper or silver filled zeolite-4A compared to pure zeolite-4A This maximum adsorption(119882max) was increased because size and volume of poreswere also increased However minimum adsorption (119882min)showed no significant difference because the increase ofaverage pore diameter allowed vapor to be evaporated easilyfrom the pores when receiving heat at temperature higherthan the boiling point Our results showed that COPs were056 for Cu6Z4A and 052 for Ag15Z4A whereas COPof Z4A was only 038 showing that adding copper and silvereffectively increased the systemCOP COP of zeolite-4A filledwith Cu yielded higher value than zeolite-4A filled with Ag
Advances in Materials Science and Engineering 7
038
044
056
048052
008 009
019
013
019
Z4A Cu4Z4A Cu6Z4A Ag4Z4A Ag15Z4A
COP
000
010
020
030
040
050
060
COP
Wmax
Figure 10 Effect of zeolite type COP
This is because of the ion exchange between sodium ion(Na+) and cations of metal Copper ion was divalent cationthat could balance framework negative charge for 2 sitesHowever silver ionwasmonovalent cation that could balanceonly 1 site Two sites exchange (copper ion) resulted in lowernumber of exchangeable cations in zeolite structure higherpore volume and higher adsorption capacity Consideringthe size of atoms and ions it was found that silver ion (Ag+126 pm) is not different than silver atom (Ag 144 pm) whilethe size of the copper ion (Cu2+ 72 pm) is more differentthan copper atom (Cu 128 pm) The BET method of bothpure and metal loaded zeolite-4A samples is given in Table 2The increase in the loading of silver in zeolite-4A causesa decrease in the surface area due to obstruction of activesite of zeolite by large size of silver ion The decrease inthe pore volume by silver loading is in agreement with thesurface area measurements An increase in the surface areawas observed for copper loading when the copper amountsexceeded a certain critical value This increase in the surfacearea is suspected to be due to the phase separation of thecopper precursors after a critical loading The data alsoshows that Cu2+ is twice smaller than Ag+ So this affectedthe maximum adsorption of water by Cu6Z4A in highervolume compared to Ag15Z4A
4 Conclusions
We were able to use Thai clay to synthesize zeolite-4A byconverting it into metakaolinite via calcination at 873K andactivation by 35molL NaOH with more than 70 yields
In testing performance of COP systems we found thatthe temperature of the adsorber and condenser affected theCOPThat is in the adsorption step as adsorber temperatureincreased adsorption was reduced decreasing COP of thesystem In desorption when adsorber temperature increaseda higher mass of refrigerant was desorbed leading to bettersystem COP
Moreover zeolite filled with copper and silver enhancessystemCOP relative to pure zeolite because copper and silverincrease pore volume which empowers water adsorptionwhich results in fast and efficient desorption of water andleads to better system COP
Nomenclature
119862119901119897 Specific heat of adsorbate in liquid phase119862119901119908 Specific heat of adsorbate in adsorbed phase
119862119901119911 Specific heat of adsorbent
COP Coefficient of PerformanceΔ119867 Heat of desorption of adsorbateK Kelvin temperature scale119871 Heat of evaporation of adsorbate119898119911 Mass of adsorbent119876des Heat of desorption119876119890 Heat of produced cooling system119876119904119889 The sensible heat of adsorbent1198791198861 Initial adsorption temperature1198791198862 Final adsorption temperature119879119888 Inside condenser temperature119879119890 Inside evaporator temperature1198791198921 Initial desorption temperature1198791198922 Final desorption temperature119882max Maximum adsorption performance119882min Minimum adsorption performance120603 Average adsorption performance
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors thank Miss Warunee Yuthphan MineralResources Development Co Ltd for providing Ranong claythe Department of Chemistry King Mongkutrsquos Institute ofTechnology Ladkrabang for acquiring the XDF XRD andSEM data and Energy Policy and Planning Office Ministryof Energy Royal Thai Government for financial support
References
[1] D C Wang Y H Li D Li Y Z Xia and J P Zhang ldquoAreview on adsorption refrigeration technology and adsorptiondeterioration in physical adsorption systemsrdquo Renewable andSustainable Energy Reviews vol 14 no 1 pp 344ndash353 2010
[2] L W Wang R Z Wang and R G Oliveira ldquoA review onadsorption working pairs for refrigerationrdquo Renewable andSustainable Energy Reviews vol 13 no 3 pp 518ndash534 2009
[3] E E Anyanwu ldquoReview of solid adsorption solar refrigerationII an overview of the principles and theoryrdquo Energy Conversionand Management vol 45 no 7-8 pp 1279ndash1295 2004
[4] K C Chan C Y H Chao G N Sze-To and K S HuildquoPerformance predictions for a new zeolite 13XCaCl
2com-
posite adsorbent for adsorption cooling systemsrdquo InternationalJournal of Heat and Mass Transfer vol 55 no 11-12 pp 3214ndash3224 2012
8 Advances in Materials Science and Engineering
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
This is because of the ion exchange between sodium ion(Na+) and cations of metal Copper ion was divalent cationthat could balance framework negative charge for 2 sitesHowever silver ionwasmonovalent cation that could balanceonly 1 site Two sites exchange (copper ion) resulted in lowernumber of exchangeable cations in zeolite structure higherpore volume and higher adsorption capacity Consideringthe size of atoms and ions it was found that silver ion (Ag+126 pm) is not different than silver atom (Ag 144 pm) whilethe size of the copper ion (Cu2+ 72 pm) is more differentthan copper atom (Cu 128 pm) The BET method of bothpure and metal loaded zeolite-4A samples is given in Table 2The increase in the loading of silver in zeolite-4A causesa decrease in the surface area due to obstruction of activesite of zeolite by large size of silver ion The decrease inthe pore volume by silver loading is in agreement with thesurface area measurements An increase in the surface areawas observed for copper loading when the copper amountsexceeded a certain critical value This increase in the surfacearea is suspected to be due to the phase separation of thecopper precursors after a critical loading The data alsoshows that Cu2+ is twice smaller than Ag+ So this affectedthe maximum adsorption of water by Cu6Z4A in highervolume compared to Ag15Z4A
4 Conclusions
We were able to use Thai clay to synthesize zeolite-4A byconverting it into metakaolinite via calcination at 873K andactivation by 35molL NaOH with more than 70 yields
In testing performance of COP systems we found thatthe temperature of the adsorber and condenser affected theCOPThat is in the adsorption step as adsorber temperatureincreased adsorption was reduced decreasing COP of thesystem In desorption when adsorber temperature increaseda higher mass of refrigerant was desorbed leading to bettersystem COP
Moreover zeolite filled with copper and silver enhancessystemCOP relative to pure zeolite because copper and silverincrease pore volume which empowers water adsorptionwhich results in fast and efficient desorption of water andleads to better system COP
Nomenclature
119862119901119897 Specific heat of adsorbate in liquid phase119862119901119908 Specific heat of adsorbate in adsorbed phase
119862119901119911 Specific heat of adsorbent
COP Coefficient of PerformanceΔ119867 Heat of desorption of adsorbateK Kelvin temperature scale119871 Heat of evaporation of adsorbate119898119911 Mass of adsorbent119876des Heat of desorption119876119890 Heat of produced cooling system119876119904119889 The sensible heat of adsorbent1198791198861 Initial adsorption temperature1198791198862 Final adsorption temperature119879119888 Inside condenser temperature119879119890 Inside evaporator temperature1198791198921 Initial desorption temperature1198791198922 Final desorption temperature119882max Maximum adsorption performance119882min Minimum adsorption performance120603 Average adsorption performance
Competing Interests
The authors declare that they have no competing interests
Acknowledgments
The authors thank Miss Warunee Yuthphan MineralResources Development Co Ltd for providing Ranong claythe Department of Chemistry King Mongkutrsquos Institute ofTechnology Ladkrabang for acquiring the XDF XRD andSEM data and Energy Policy and Planning Office Ministryof Energy Royal Thai Government for financial support
References
[1] D C Wang Y H Li D Li Y Z Xia and J P Zhang ldquoAreview on adsorption refrigeration technology and adsorptiondeterioration in physical adsorption systemsrdquo Renewable andSustainable Energy Reviews vol 14 no 1 pp 344ndash353 2010
[2] L W Wang R Z Wang and R G Oliveira ldquoA review onadsorption working pairs for refrigerationrdquo Renewable andSustainable Energy Reviews vol 13 no 3 pp 518ndash534 2009
[3] E E Anyanwu ldquoReview of solid adsorption solar refrigerationII an overview of the principles and theoryrdquo Energy Conversionand Management vol 45 no 7-8 pp 1279ndash1295 2004
[4] K C Chan C Y H Chao G N Sze-To and K S HuildquoPerformance predictions for a new zeolite 13XCaCl
2com-
posite adsorbent for adsorption cooling systemsrdquo InternationalJournal of Heat and Mass Transfer vol 55 no 11-12 pp 3214ndash3224 2012
8 Advances in Materials Science and Engineering
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
[5] P H Grenier J J Guilleminot F Meunier and M Pons ldquoSolarpowered solid adsorption cold storerdquo ASME Journal of SolarEnergy Engineering vol 110 no 3 pp 192ndash197 1988
[6] M Tatlier and A Erdem-Senatalar ldquoThe effects of thermalgradients in a solar adsorption heat pump utilizing the zeolite-water pairrdquoAppliedThermal Engineering vol 19 no 11 pp 1157ndash1172 1999
[7] M Pons and J J Guilleminot ldquoDesign of an experimental solar-powered solid-adsorption ice makerrdquo Journal of Solar EnergyEngineering Transactions of the ASME vol 108 no 4 pp 332ndash337 1986
[8] P Hu J-J Yao and Z-S Chen ldquoAnalysis for composite zeo-litefoam aluminum-water mass recovery adsorption refriger-ation system driven by engine exhaust heatrdquo Energy Conversionand Management vol 50 no 2 pp 255ndash261 2009
[9] S Biloe V Goetz and S Mauran ldquoCharacterization of adsor-bent composite blocks formethane storagerdquoCarbon vol 39 no11 pp 1653ndash1662 2001
[10] G Restuccia A Freni F Russo and S Vasta ldquoExperimentalinvestigation of a solid adsorption chiller based on a heatexchanger coated with hydrophobic zeoliterdquo Applied ThermalEngineering vol 25 no 10 pp 1419ndash1428 2005
[11] H Zhao M Zhang J Lv G Yu and Z Zou ldquoThermalconductivities study of new types of compound adsorbentsused in solar adsorption refrigerationrdquo Energy Conversion andManagement vol 50 no 5 pp 1244ndash1248 2009
[12] S Chandrasekhar P Raghavan G Sebastian and A DDamodaran ldquoBrightness improvement studies on lsquokaolin basedrsquozeolite 4ArdquoApplied Clay Science vol 12 no 3 pp 221ndash231 1997
[13] S Trisupakitti J Jamradloedluk and S WiriyaumpaiwongldquoSynthesis and characterization of 4A-zeolite devived fromThaikaolinrdquo in Proceedings of the 5th International Conference onScience Technology and Innovation for Sustainable Well-Being(STISWB V rsquo13) September 2013
[14] G Cacciola and G Restuccia ldquoReversible adsorption heatpump a thermodynamic modelrdquo International Journal ofRefrigeration vol 18 no 2 pp 100ndash106 1995
