IJIRAE:: Experimental Study of the Counter Flow Regenerator with Structure Packing

International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163 Issue 6, Volume 2 (June 2015) www.ijirae.com

_________________________________________________________________________________________________ 2014-15, IJIRAE- All Rights Reserved Page -130

Experimental Study of the Counter Flow Regenerator with Structure Packing

Raman Kumar Rakesh Kumar

Research Scholar, M. Tech. Assisstant Professor PTU regional Centre IET Bhaddal Ropar Mechanical Engg. Deptt., IET Bhaddal

Abstract Regenerator is very important part of the desiccants dehumidifier system. It is used to regain the concentration of the solution by removing the moisture from the solution so that it can be reuse. The celdek pads as packing material and lithium bromide as the desiccant has been used in the regeneration system. The counter flow of air and desiccant solution is selected in the current research paper. The effect of solution flow rate and air inlet temperature will be studied on different outlet parameter; the evaporation rate, regenerator effectiveness, out let dry bulb temperature of the air, %age change in the concentration and solution outlet temperature The results show that there is increment in the evaporation rate and regenerator effectiveness with increase these inlet parameters.

Keywords lithium bromide, regenerator,& celdek packing,dehumidifier,counter flow

I. INTRODUCTION

In conventional method the dehumidification done by the cooling coil, by cool the air up to the dew point temperature at this point water present in the air start to condense and separated from the air, then air is heated to desired temperature, thus have to do extra work to heat the air. Desiccant dehumidifier is the alternative way to remove the moisture contents from the air and also takes the latent heat load from the air. The function of the desiccant is based on the vapour pressure difference between the desiccant solution and the inlet air vapour pressure. The difference between vapour pressure act the driving force for the moisture contents to move from the higher vapour pressure to the lower vapour pressure side. Desiccant is a material have tendency to absorb the moisture up to great extend, desiccant may be solid (silica gel) or liquid (CaCl2, LiCl, LiBr & TEG) On the basis of the desiccant there are two types of the desiccant cooling system:-

Solid desiccant system Liquid desiccants system

Fig.1Function of the solid desiccant system

The Fig.1 shows the function of the solid desiccant system, having the one wheel which contains the desiccant. Wheel is divided into two part one part is work as the dehumidifier and another act as the regenerator. The liquid desiccants having the two different chamber one work as the dehumidifier which used to dehumidify the air and other work as the regenerator which used to regenerate the desiccant solution so that we can re-circulate the solution. There are some advantage of using the liquid desiccants over the solid desiccants One of the important advantages of liquid desiccant is that it can remove the latent heat of the processed air and regenerate it with low temperature using free energy such as solar and waste energy[1], regeneration temperature required for liquid desiccants are lower, pressure drop through a liquid desiccant system is smaller than the pressure drop through a solid desiccant wheel and the dehumidification process scrubbing of air stream takes place which provides a cleansing action an it inhibits microbial growth[2].The benefits of the Desiccant dehumidifier system are reduce the possibility that you will develop mold on your clothing, furniture, increases comfort of building occupants, reduces conventional cooling requirement, prevents fungus growth and bacterial growth in ducts and stabilize humidity levels in your home and insure your family's health and comfort. The applications of the Desiccant dehumidifiers are used in commercial swimming pool and spa rooms in hotels, health clubs.



The desiccant dehumidifier have critical roles in industries such as, Food packaging and processing, Printing, Grinding and machining.

II. LITERATURE REVIEW In experimental study using TEG as the Desiccant with aluminium and wood as the packing materials and the result from the study that moisture removal rate and the effectiveness both are increases as the concentration of the solution is varies from the 93% to 98%[3]. The three dehumidifiers are tested experimentally by using different types of the packing, Concluded that the rougher surface could do better than a smoother surface in dehumidification. Beyond that, if the air humidity is low and the effectiveness of the system can be increases by combining a normal packing staff with solid desiccant[4].The dehumidification and the regenerator system can be used by using the mixture of the two desiccant solution. The mixture of the LiCl and the CaCl2 with over all concentration is 40% tested and the results show that mixture of 20 wt% CaCl2 and 20 wt% LiCl is found to be close to the performance of 45 wt% solution of calcium chloride[5]. A detailed experimental of the investigation of the performance of the gaugetypes structured packing dehumidifier with variation of the desiccant flow rate from the 10 to 32 litter per minute, desiccant inlet concentration 38.5 to 41% and the inlet absolute humidity 0.014-0.039 is preformed as the results show that performance of the dehumidifier decreases as the desiccant flow rate increases or the concentration of the desiccant at the inlet is increased [6].A experimental with cross flow dehumidifier using libr as the desiccant solution system. The results show the similar variation as the counter flow from the literature studies [7]. A cross flow regenerator with libr desiccant investigated and the various result like Moisture removal rate, Regenerator effectiveness with the variation of the inlet perimeter desiccant flow rate, inlet concentration of the solution.[8] The dehumidifier moisture removal rate studied with the three different packing materials density (77, 100 and 200 m2/m3). The desiccant used in the study was TEG. In this study the solution flow rate was very low, the objective of the study to use the multiple regression method and the principle component analysis to find the predication model for the moisture removal rate and the dehumidification effectiveness [9]. The two desiccants the CaCl2 and the CaCl2.2H2O solution are tested for the dehumidification/regeneration process. The objective is to find the better desiccant out of these two during the experiment it is investigated that in the dehumidification process the mass transfer potential of Cacl2 solution is better than that of CaCl2.2H2O solution and in the regeneration the CaCl2 solution is drier than the CaCl2.2H2O solution. Thus the Cacl2 is the better desiccant solution than the CaCl2.2H2O solution [10]. A structured packing cross flow desiccant dehumidifier system (DDS) using CaCl2 solution as desiccant is designed and experimentally tested. The structured packing has a density (specific surface area) of 390 m2/m3, corrugation angle of 60 and void fraction of 0.88. The remarkable increase of mass transfer coefficient and MRR for both dehumidifier/regenerator is observed by increasing both air and solution flow rates. Eventually, the payback period (PP) of the DDS is 11 months with annual running cost savings (DCRC) of about 31.24% compared with vapour compression system (VCS) dehumidification. The overall environmental impacts of DDS are nearly 0.63 of VCS [11]. A simplified theoretical model is used to investigate the complex phenomena of simultaneous heat and mass transfer, as well as the interaction between the air dehumidification and the used desiccant regeneration processes powered by the solar or any low thermal energy sources. The results show that the cooling of the air dehumidification process enhances the mass transfer, makes the operation more efficient and compact and reduces the desiccant strong solution requirements [12]. The performance parameter reduction ratio of the air humidity ratio and the dehumidifier effectiveness of the liquid desiccant dehumidifier system that utilizes calcium chloride solution as a liquid desiccant is evaluate numerically [13]. The packed type of the regenerator is investigated in the study with CaCl2 as the desiccant. The conclusions are given after study evaporation rate of water from the desiccant increases with increase of air and solution inlet parameters, flow rate and temperature. it is also found that the regeneration rate decreases with an increase in humidity ratio of inlet air and solution inlet concentration[14]. By the experimental study of the cross flow regenerator of dehumidification system with PVC packing material and TEG desiccant concluded that the change in desiccant concentration and mass evaporation rate increases with mass flow rate of air at different inlet solution temperatures [15]. After the review the various hybrid liquid desiccant air conditioning system technologies, the result shows that the application of hybrid liquid desiccant air conditioning system based vapour compression unit minimizes the electric power consumption of VCS and its size and increases the COP[16]. In the experiments have been conducted on Vapour Compression Hybrid Air- Conditioner system. In this system the desiccant system is coupled with the evaporator of the vapour compression system and takes the load from the evaporator, while regenerator coupled with the condenser and takes the heat from the condenser. The conclusion of the experiment is that conclude that the DAC systems are the most suitable to be introduced at hot and humid climates [17].

III. EXPERIMENTAL SET UP AND PROCEDURE

The Fig.2 shows the experiment setup. The parts show in the set up are desiccant solution tank (inlet) used to store the lithium bromide desiccant solution, External heater to increase the temperature of the desiccant solution, Pump used to circulate the desiccant solution, control valve used to control the flow of the desiccant solution, Rota-meter used to read the mass flow rate of the solution delivered to the regeneration tank, Regeneration chamber with packing celdek material size (55cm28cm35cm). Desiccant solution tank (outlet) used to collect the desiccant solution after passing through the regeneration tank; Blower is connected to inlet duct of the regeneration tank used to force the air to pass through the packing,



Fig.2 Block Diagram of the experimental setup

The procedure follow for investigate the outlet parameter of the regenerator , Start the pump and set the control valve to get the desired mass flow rate of the desiccant solution, solution will start to flow through the regeneration tank now start the blower air will also start to flow through the regeneration tank. Wait till the system is not get steady after the steady state after the steady note the various reading like inlet and outlet DBT &WBT of the air by psychometric thermometer, Solution inlet and outlet temperature by the thermocouple, density of the desiccant solution at inlet and outlet by the hydrometer. Same procedure is repeated by variation of different inlet parameter i.e. the mass flow rate control by the control valve, mass flow rate is control by the control the speed of the blower. For variation temperature and the humidity of the inlet air we conduct the experiment on the different days and different time in the day.

IV. PERFORMANCE EQUATION

The performance of the regenerator is described by the regenerator effectiveness and evaporation rate [18]. Equations used to calculate the outlet parameters are given:-

= (Wo-Wi)/(Weq-Wi) Eq.1 Mw = ( Wo Wi) a A Eq.2 % Z =(Zo-Zi)/Zi100 Eq.3

V. RESULT AND DISCUSSION The five outlet parameter (air outlet temperature, solution outlet temperature of the solution, evaporation rate,

regenerator effectiveness and % change in the concentration of the desiccant solution) are studied by variation of the mass flow rate of the solution and the variation of the Tai. These experiments conducted for three inlet solution temperature are 45 C, 50C and 55C.

A. Effect of variation of mass flow rate of the solution on the outlet parameter. The figure 3,4,5,6 and 7 show the effect on the outlet parameter by variation of the mass flow rate. The range of the

mass flow rate 0.0111kg/s to 0.0335 kg/s, The air flow rate almost constant is 0.0146 kg/s, humidity at the inlet is varied from 0.014 kg/kg to 0.016 kg/kg, concentration of the desiccant solution is 37.4 %.With increase in the mass flow rate of the solution desiccants have ability to wet more surface area of the packing material, as the more packing getting wet the contact between the air and solution is increased due to this the heat and mass transfer rate between air and the desiccants solution is increased .Thus the outlet temperature of the solution is decreased and the temperature of the outlet air is increased(Fig.3&Fig.4), similarly the water vapour present in the solution is start to flow towards the air as the % change in the concentration is also increase(Fig.5) because of high temperature of the solution also ensure that having the higher vapour pressure than the air. When % change of the concentration is increased means the desiccant solution is get stronger by remove the vapour inlet thus the evaporation rate also increases as more vapour are get transfer(Fig.7). By incesening the evaporation rate effectiveness of the regenerator also increases (Fig.6).



Fig. 3 Effect of the mass flow rate (s) at the solution outlet temperature(Tso)

Fig.4 Effect of the mass flow rate (s) at dry bulb temperature of the air (Tao)

Fig.5 Effect of the mass flow rate (s) on the % Change in concentration of the desiccant (%Z)

Fig.6 Effect of the mass flow rate (s) on the regenerator effectiveness ()



Fig.7 Effect of the mass flow rate (s) on the evaporation rate (Mw)

B. Effect of variation of inlet temperature of the air on the outlet parameter.

The figure 3,4,5,6 and 7 show the effect on the outlet parameter by variation of the dry bulb temperature at the inlet (Tai) of the regenerator. The range of the Tai is 35 C to 39 C. The air flow rate (Ma) and mass flow rate (s) almost constant is 0.0146 kg/s and 0.0278 Kg/s respectively. The concentration of the lithium bromide is 37.4%. As the dry bulb temperature of the air is increased the heat transfer between the desiccant solution and the air is increased due to which the vapour pressure at the surface of the solution get increased this give the more potential to vapour to moves towards the air because of this evaporation rate and the effectiveness of the regenerator is increased (Fig.11 & Fig.12). Due to leaving the vapour particles the solution at the outlet of the regenerator also become stronger thus the % change in the concentration also increased (Fig.10). The solution temperature at the outlet and the air dry bulb temperature increases due to heat transfer between the solution and the air (Fig.8 & Fig 9).

Fig.8 Effect of inlet dry bulb temperature of air (Tai) on the outlet temperature of the solution (Tso)

Fig.9 Effect of inlet dry bulb temperature of air (Tai) on the outlet dry bulb temperature of air (Tao)



Fig.10 Effect of inlet dry bulb temperature of air (Tai) on the % Change in concentration of the desiccant (%Z)

Fig. 11Effect of inlet dry bulb temperature of air (Tai) on the regenerator effectiveness ()

Fig.12 Effect of inlet dry bulb temperature of air (Tai) on the evaporation rate (Mw)

VI. CONCLUSIONS In this experimental we are study the outlet parameter investigates by the variation of the mass flow rate of the

solution and the inlet dry bulb temperature. We concluded that the performance parameter evaporation rate and the effectiveness of the regenerator are increased as we increase the mass flow rate and the inlet dry bulb temperature of the air. The % change in the concentration is increases for the both cases. But the temperature of the solution is increased as we increases the mass flow rate but decreases as we increase the inlet dry bulb temperature. The outlet dry bulb temperature is increases for the both cases.

ACKNOWLEDGMENT We would like to thank to the Punjab Technical University, IET Roper to give us opportunity to carry out this

research work.



NOMENCLATURE DBT = Dry bulb temperature (C). WBT= Wet Bulb temperature(C) a = Mass flow rate of the air(kg/s) s = Mass flow rate of the solution (kg/s) Mw = Evaporation rate (g/s). Tai= Dry bulb temperature at inlet (C) Tao= dry bulb temperature at outlet (C) = Regenerator effectiveness. Wi= Specific Humidity at the inlet (kg/kg). Wo = Specific Humidity at outlet (kg/kg). Weq = specific Humidity at the equilibrium (kg/kg). Zi = Concentration of the solution at inlet. Zo = concentration of the solution at outlet. Z = Change in the concentration(%). A= Area of the outlet duct (m2)

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IJIRAE:: Experimental Study of the Counter Flow Regenerator with Structure Packing

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