(##)Electrolux Refrigeration Using Solar Heat (Solar Refrigeration)

7/29/2019 (##)Electrolux Refrigeration Using Solar Heat (Solar Refrigeration)

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ELECTROLUX REFRIGERATION USING SOLAR HEAT

PROJECT REPORT

Submitted in partial fulfillment of the requirementsfor the award of the Degree of Bachelor of Technology

in Mechanical Engineering to the

University of Kerala

Submitted by

KIRAN P R

PADMAKUMAR R

PRATHEESH S BABU

RAMAN RAJENDRAN

Department of Mechanical Engineering

College of Engineering, Thiruvananthapuram 16

April, 2009


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DEPARTMENT OF MECHANICAL ENGINEERING

COLLEGE OF ENGINEERING, TRIVANDRUM 16

CERTIFICATE

This is to certify that the project report entitled Electrolux refrigeration using solar heat

submitted by KIRAN P R, PADMAKUMAR R, PRATHEESH S BABU and RAMAN

RAJENDRAN to the University of Kerala in partial fulfillment of the requirement for the

award of the Degree of Bachelor of Technology in Mechanical Engineering is a bonafide

work carried out under our guidance and supervision. The contents of this work in full or

parts have not been submitted in any other institute or University for the award of any

degree or diploma.

Dr. N. Asok Kumar Dr. B Anil

Assistant Professor Professor & Head

Dept. of Mechanical Engineering Dept. of Mechanical EngineeringCollege of Engineering Trivandrum College of Engineering Trivandrum


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ACKNOWLEDGEMENT---------------------------------------------------------------------------------


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ACKNOWLEDGEMENTS

We would like to take this opportunity to extend our gratitude to our guide Dr N. Asok

Kumar for his timely advice and inputs without which we would not have been able to

complete this project. The several sessions we spent with him on finding new paths

regarding the direction of the project was quite educational. Any expression of gratitude

cannot be deemed complete without mentioning the role played by our Head of the

Department, Dr. B. Anil for giving us total freedom to make the maximum utilization of

the departmental resources. We would also like to express our gratitude to the

technicians at Super cold refrigeration system, Mr. Dilakan, Mr. John M.G engineer at

Thermax India Ltd and Steve Hammerling, Assistant Manager of Research & Technical

Services American Society of Heating, Refrigerating and Air-Conditioning Engineers,

Inc.(ASHRAE) for technical assistance provided during the course of the project.

We also thank our classmates and seniors for their suggestions especially our seniors

Sabu V.G, Shibu K.R, Shome V.S, Santhosh K, Roby Sebastian for valuable ideas

imparted during the formation of this project. To summarize, it has been quite an

experience and we extend our sincere gratitude to all those whom we have missed, for

positive comments they put in and cooperation they all extended were vital for the

successful completion of this project.


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REFRIGERATOR---------------------------------------------------------------------------------


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CONTENTS---------------------------------------------------------------------------------

CONTENTS


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CHAPTER PARTICULAR

PAGE No.

ACKNOWLEDGEMENT

1. SYNOPSIS

2. INTRODUCTION

3. REVIEW OF LITERATURE

4. BATTERY

5. THERMO ELECTRIC ZIP COOLER

6. CONDENSER

7. D.C BLOWER

8. WORKING PRINCIPLE

9. LIST OF MATERIALS

10. COST ESTIMATION

11. ADVANTAGES AND DISADVANTAGES

12.APPLICATIONS

13.CONCLUSION

APPENDIX

BIBLIOGRAPHY

PHOTOGRAPHY

ACKNOWLEDGEMENTS


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We would like to take this opportunity to extend our gratitude to our guide Dr N. Asok

Kumar for his timely advice and inputs without which we would not have been able to

complete this project. The several sessions we spent with him on finding new paths

regarding the direction of the project was quite educational. Any expression of gratitude

cannot be deemed complete without mentioning the role played by our Head of the

Department, Dr. B. Anil for giving us total freedom to make the maximum utilization of

the departmental resources. We would also like to express our gratitude to the

technicians at Super cold refrigeration system, Mr. Dilakan, Mr. John M.G engineer at

Thermax India Ltd and Steve Hammerling, Assistant Manager of Research & Technical

Services American Society of Heating, Refrigerating and Air-Conditioning Engineers,

Inc.(ASHRAE) for technical assistance provided during the course of the project.

We also thank our classmates and seniors for their suggestions especially our seniors

Sabu V.G, Shibu K.R, Shome V.S, Santhosh K, Roby Sebastian for valuable ideas

imparted during the formation of this project. To summarize, it has been quite an

experience and we extend our sincere gratitude to all those whom we have missed, for

positive comments they put in and cooperation they all extended were vital for the

successful completion of this project.

ABSTRACT


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The project consists of an Electrolux refrigeration system using solar energy as input.

This system was actually invented by two Swedish engineers, Von Platen and Carl

Munters. The idea was first developed by the Electrolux Company, of Luton, England,

hence the name Electrolux refrigeration system. The principle behind Electrolux

refrigeration is that it uses three gases to accomplish its cooling effect namely ammonia

(refrigerant) water (absorbent) and hydrogen. Ammonia is used as the refrigerant as it is

easily available, environmentally friendly and can produce a better cooling effect.

Hydrogen is used to reduce the partial pressure of ammonia vapour in the evaporator

chamber so that more ammonia evaporates yielding more cooling effect. Heat input is

required at the generator where aqua ammonia is heated to get ammonia vapors. In this

project, an experimental setup for Electrolux refrigeration is made using solar energy to

supply input heat. A double involute cusp shaped plate is used as the solar collector. Two

1 diameter pipes welded together is placed at the focal point of the involute cusp which

acts as the generator pipes. Solar energy is concentrated to these pipes by the solar

collector, heating the aqua ammonia solution. The rest of the system is unaltered.

CONTENTS


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INTRODUCTION


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If the solar energy possesses the advantage to be "clean", free and renewable, this last is

probably, considered like an adapted potential solution, that answers in even time at a

economic preoccupation and ecological problems. Among the main done currently

research is the use of this free source to make operate system of refrigeration. Since

among the domestic appliances used today, refrigerators consume a considerable amount

of energy, using solar energy to run refrigerator is of great practical relevance nowadays.

The diffusion absorption refrigerator cycle invented in the 1920s is based on ammonia

(refrigerant) and water (absorbent) as the working fluids together with hydrogen as an

auxiliary inert gas. Since there are no moving parts in the unit, the diffusion absorption

refrigerator system is both quiet and reliable. The system is, therefore, often used in hotel

rooms and offices. The absorption diffusion refrigerating machine is designed according

to the operation principle of the refrigerating machine mono pressure invented by

PLATERN and MUNTER. This machine uses three operation fluids, water (absorbent),

the ammonia (refrigerant) and hydrogen as an inert gas used in order to maintain the total

pressure constant

LITERATURE REVIEW


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1. VAPOR ABSORPTION REFRIGERATION IN ROAD TRANSPORT

VEHICLES, J. Energy Engrg. Volume 125, Issue 2, pp. 48-58 (August 1999)

Abstract

This study includes an experimental investigation into the use of vapor absorption

refrigeration (VAR) systems in road transport vehicles using thewaste heat in the exhaust

gases of the main propulsionunit as the energy source. This would provide an alternative

to the conventional vapor compression refrigeration system and its associated internal

combustion engine. The performance of a VAR system fired by natural gas is compared

with that of the same

system driven by engine exhaust gases. This showed that the

exhaust-gas-driven system produced the same performance characteristics as the gas-

fired system. It also suggested that, with careful design, inserting the VAR system

generator into the main engine exhaust system need not impair the performance of the

vehicle propulsion unit. Acomparison of the capital and running costs of the conventional

and proposed alternative system is made.

2. DESIGN AND SIMULATION OF AN ABSORPTION DIFFUSION SOLAR

REFRIGERATION UNIT by B. Chaouachi, S. Gabsi (American Journal of

Applied Sciences , Feb, 2007)

Abstract

The purpose of this study was the design and the simulation of an absorption diffusion

refrigerator using solar as source of energy, for domestic use. The design holds account

about the climatic conditions and the unit cost due to technical constraints imposed by

the technology of the various components of the installation such as the solar generator,

the condenser, the absorber and the evaporator. Mass and energy conservation equations
http://findarticles.com/p/search/?qa=B.%20Chaouachihttp://findarticles.com/p/search/?qa=S.%20Gabsihttp://findarticles.com/p/articles/mi_7109/http://findarticles.com/p/articles/mi_7109/http://findarticles.com/p/search/?qa=B.%20Chaouachihttp://findarticles.com/p/search/?qa=S.%20Gabsihttp://findarticles.com/p/articles/mi_7109/http://findarticles.com/p/articles/mi_7109/


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were developed for each component of the cycle and solved numerically. The obtained

results showed, that the new designed mono pressure absorption cycle of ammonia was

suitable well for the cold production by means of the solar energy and that with a simple

plate collector we can reach a power, of the order of 900 watts sufficient for domestic

use.

3 INTERNATIONAL JOURNAL OF REFRIGERATION (Volume 31, Issue 4,

June 2008, Pages 545-551 Refrigeration with Ammonia and Hydrocarbons) by Andy

Pearson, Star Refrigeration Ltd., Glasgow G46 8JW, UK,

Abstract

Ammonia is widely used as a refrigerant in industrial systems for food refrigeration,

distribution warehousing and process cooling. It has more recently been proposed for use

in applications such as water chilling for air-conditioning systems but has not yet

received widespread acceptance in this field. This review paper assesses the reasons why

ammonia is so popular in industrial systems, the reasons why it is deemed less suitable

for other applications and the possible benefits at local, national and international levels

that might be gained by more general acceptance of ammonia as a refrigerant. The paper

also considers other possible applications which might benefit from the use of ammonia

as refrigerant.

4 UNDERSTANDING SOLAR ENERGY: A GENERAL OVERVIEW by

Mr. Ajay Prakash Shrivastava, President, Solar Energy Society of India (SESI).

Abstract
http://www.sciencedirect.com/science/journal/01407007http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235765%232008%23999689995%23691306%23FLA%23&_cdi=5765&_pubType=J&view=c&_auth=y&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=724fb91da3985a63d4909113e5e6a425http://www.sciencedirect.com/science/journal/01407007http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235765%232008%23999689995%23691306%23FLA%23&_cdi=5765&_pubType=J&view=c&_auth=y&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=724fb91da3985a63d4909113e5e6a425


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India is one of the few countries with long days and plenty of sunshine. This zone, having

abundant solar energy available, is suitable for harnessing solar energy for a number of

applications. In areas with similar intensity of solar radiation, solar energy could be easily

harnessed. Solar thermal energy is being used in India for heating water for both

industrial and domestic purposes. A 140 MW integrated solar power plant is to be set up

in Jodhpur but the initial expense incurred is still very high. India is getting a solar

irradiation of 500W/m2.

5 UNDERSTANDING SOLAR CONCENTRATORS by George M. Kaplan,

VITA Volunteer, President of KAPL Associates.

Abstract

Solar thermal technology is concerned principally with the utilization of solar energy by

converting it to heat. In the concentrating type of solar collector, solar energy is collected

and concentrated so that higher temperatures can be obtained; the limit is the surface

temperature of the sun.. Similarly, overall efficiency of energy collection, concentration,

and retention, as it relates to energy cost, imposes a practical limit on temperature

capability.. The cusp collector whose surface geometry is the locus of the position of the

end of a string as it is unwrapped from a pipe can provide a modest concentration suitable

to boil water.

6 LOW REFLECTION LOSS CUSP LIKE REFLECTOR FOR SOLAR

ENERGY COLLECTOR by Raymond H.Lambert, Generic electric

company, Philadelphia. (US patent 4246891, Jan 27 1981)


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Abstract

There is disclosed the manner in which a reflector for a solar energy collector is designed.

The absorber is a right circular cylinder and is contained in an evacuated glass shroud.

The glass shroud prevents the use of the reflector design technique of the prior art, and

instead calculations are performed as if an absorber having a smaller diameter were to be

used.

7 REFLECTOR WITH CURVED DUAL INVOLUTE SURFACES by Fred A

Plofchan (US Patent 4843521, Jun 27 1989)

Abstract

A wide angle flash tube reflector has dual involute surfaces thereon intersecting at a cusp

and bent in the horizontal to intercept light from a light source adjacent the cusp and to

reflect such light in a dispersion pattern that spreads the flash coverage to match extended

light coverages of lenses from a normal focal length to extreme wide angle. One light

source is in the form of a bent tube having adjustable positioned cathode and anode

electrodes for varying the length of a plasma arc to control the extent of the dispersion

pattern reflected from the dual involute surfaces.

PROJECT OUTLINE
http://www.patentstorm.us/patents/4843521/description.htmlhttp://www.patentstorm.us/patents/4843521/description.html


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When we started with our project, we were planning to utilize the nonconventional

energy resources like solar energy for domestic purposes. While considering the power

utilization of various domestic appliances, by knowing that a major amount of power is

drawn by refrigerators, we planned to make use of solar energy to drive refrigerators

which will be more economical with less wastage of electrical power. Mostly used

refrigerator systems are vapour absorption and vapour compression of which vapour

absorption system is more suitable when heat is used as the energy input. Our studies

about the vapour absorption system led to the conclusion that Electrolux refrigeration

system is best suitable for domestic purpose as it consumes less energy. Since the

Electrolux system uses no pump for its working, the only energy input is in the form of

heat at the generator pipe. An Electrolux system also called Platen-Munters system uses

three fluids for its operation viz Ammonia, Water and Hydrogen. Hence the system is

also called Three Fluid System.

We got an old Electrolux refrigeration system from the dump yard of the heat engines lab

in our college. We inspected the system with the help of a professional fridge mechanic

and came to a conclusion that the existing system cannot be pressurized as its piping was

totally damaged. We came to know that similar system is used as mini bar in star hotels.

We managed to get an obsolete Electrolux refrigerator from Leela Kempinski Hotel,

Kovalam.

Our next aim was to modify the existing system so that its running cost is zero. For this,

we decided to modify the existing system by replacing the heating unit with a solar

heating device (solar collector).


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Experiments so far conducted show that for effective liberation of ammonia vapour from

ammonium hydroxide solution, the temperature should be above 88oC. After lot of

studies about various solar concentrating devices, it was found that the concentration

ratio of involute cusp shaped collector is comparatively high with a wide acceptance

range. Besides this, the collector has an advantage that it is non-tracking. The reflecting

surface was coated with mirror plastic in order to increase the reflectivity.

The generator pipe is made of two 1 MS pipe welded together. Holes were provided for

pressure gauge valve, inlet, exit and ammonia charging at appropriate positions.

The next step was to fix the position of the collector. Since the fluid circulation in

Electrolux system is completely controlled by buoyancy change and gravity, the position

of the generator is crucial. Thus the collector-generator assembly is fixed at the bottom of

the fridge between the absorber tank and the vapour lift tube.

The charging of ammonia was done by making ammonium hydroxide solution of

adequate concentration. Hydrogen was charged through the hydrogen charging line

provided at the absorber tank.

REFRIGERATION

Refrigeration is the process of removing heat from an enclosed space, or from a

substance, and moving it to a place where it is unobjectionable. The primary purpose of


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refrigeration is lowering the temperature of the enclosed space or substance and then

maintaining that lower temperature. The term cooling refers generally to any natural or

artificial process by which heat is dissipated. The process of artificially producing

extreme cold temperatures is referred to as cryogenics.

Cold is the absence of heat, hence in order to decrease a temperature, one "removes heat",

rather than "adding cold." In order to satisfy the Second Law of Thermodynamics, some

form of work must be performed to accomplish this. This work is traditionally done by

mechanical work but can also be done by magnetism, laser or other means.

The first known method of artificial refrigeration was demonstrated by William Cullen at

the University of Glasgow in Scotland in 1756. Cullen used a pump to create a partial

vacuum over a container of diethyl ether, which then boiled, absorbing heat from the

surrounding air. The experiment even created a small amount of ice, but had no practical

application at that time.

In 1805, American inventorOliver Evans designed but never built a refrigeration system

based on the vapor-compression refrigeration cycle rather than chemical solutions or

volatile liquids such as ethyl ether.

In 1820, the British scientist Michael Faraday liquefied ammonia and other gases by

using high pressures and low temperatures.
http://en.wikipedia.org/wiki/William_Cullenhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Diethyl_etherhttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Heat_of_vaporizationhttp://en.wikipedia.org/wiki/Oliver_Evanshttp://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Michael_Faradayhttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/William_Cullenhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Diethyl_etherhttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Heat_of_vaporizationhttp://en.wikipedia.org/wiki/Oliver_Evanshttp://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Michael_Faradayhttp://en.wikipedia.org/wiki/Ammonia


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First refrigeration systems

The first known method of artificial refrigeration was demonstrated by William Cullen at

the University of Glasgow in Scotland in 1756. Cullen used a pump to create a partial

vacuum over a container of diethyl ether, which then boiled, absorbing heat from the

surrounding air. The experiment even created a small amount of ice, but had no practical

application at that time. In 1805, American inventor Oliver Evans designed but never

built a refrigeration system based on the vapor-compression refrigeration cycle rather

than chemical solutions or volatile liquids such as ethyl ether. In 1820, the British

scientist Michael Faraday liquefied ammonia and other gases by using high pressures and

low temperatures. An American living in Great Britain, Jacob Perkins, obtained the first

patent for a vapor-compression refrigeration system in 1834. Perkins built a prototype

system and it actually worked, although it did not succeed commercially.

The first gas absorption refrigeration system using gaseous ammonia dissolved in water

(referred to as "aqua ammonia") was developed by Ferdinand Carr of France in 1859

and patented in 1860. Due to the toxicity of ammonia, such systems were not developed

for use in homes, but were used to manufacture ice for sale. In the United States, the

consumer public at that time still used the ice box with ice brought in from commercial

suppliers, many of whom were still harvesting ice and storing it in an icehouse.

Current applications of refrigeration

Probably the most widely-used current applications of refrigeration are for the air-

conditioning of private homes and public buildings, and the refrigeration of foodstuffs in
http://en.wikipedia.org/wiki/William_Cullenhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Diethyl_etherhttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Heat_of_vaporizationhttp://en.wikipedia.org/wiki/Oliver_Evanshttp://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Michael_Faradayhttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Jacob_Perkinshttp://en.wikipedia.org/wiki/Absorption_refrigerationhttp://en.wikipedia.org/wiki/Ferdinand_Carr%C3%A9http://en.wikipedia.org/wiki/Ice_boxhttp://en.wikipedia.org/wiki/Icehouse_(building)http://en.wikipedia.org/wiki/William_Cullenhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Diethyl_etherhttp://en.wikipedia.org/wiki/Boiling_pointhttp://en.wikipedia.org/wiki/Heat_of_vaporizationhttp://en.wikipedia.org/wiki/Oliver_Evanshttp://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Michael_Faradayhttp://en.wikipedia.org/wiki/Ammoniahttp://en.wikipedia.org/wiki/Jacob_Perkinshttp://en.wikipedia.org/wiki/Absorption_refrigerationhttp://en.wikipedia.org/wiki/Ferdinand_Carr%C3%A9http://en.wikipedia.org/wiki/Ice_boxhttp://en.wikipedia.org/wiki/Icehouse_(building)


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homes, restaurants and large storage warehouses. The use of refrigerators in our kitchens

for the storage of fruits and vegetables has allowed us to add fresh salads to our diets year

round, and to store fish and meats safely for long periods.

In commerce and manufacturing, there are many uses for refrigeration. Refrigeration is

used to liquify gases like oxygen, nitrogen, propane and methane for example. In

compressed air purification, it is used to condense water vapor from compressed air to

reduce its moisture content. In oil refineries, chemical plants, andpetrochemical plants,

refrigeration is used to maintain certain processes at their required low temperatures (for

example, in the alkylation ofbutenes and butane to produce a high octane gasoline

component). Metal workers use refrigeration to temper steel and cutlery. In transporting

temperature-sensitive foodstuffs and other materials by trucks, trains, airplanes and sea-

going vessels, refrigeration is a necessity.

Dairy products are constantly in need of refrigeration, and it was only discovered in the

past few decades that eggs needed to be refrigerated during shipment rather than waiting

to be refrigerated after arrival at the grocery store. Meats, poultry and fish all must be

kept in climate-controlled environments before being sold. Refrigeration also helps keep

fruits and vegetables edible longer.

TERMS IN REFRIGERATION

Coefficient of Performance (COP)

The coefficient of performance or COP, of a refrigeration system is the ratio of the heat

removed from the cold reservoir to input work.
http://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Propanehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Oil_refinerieshttp://en.wikipedia.org/wiki/Chemical_planthttp://en.wikipedia.org/wiki/Petrochemicalhttp://en.wikipedia.org/wiki/Alkylationhttp://en.wikipedia.org/wiki/Butenehttp://en.wikipedia.org/wiki/Butanehttp://en.wikipedia.org/wiki/Octane_ratinghttp://en.wikipedia.org/wiki/Heat_pumphttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Propanehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Condensationhttp://en.wikipedia.org/wiki/Oil_refinerieshttp://en.wikipedia.org/wiki/Chemical_planthttp://en.wikipedia.org/wiki/Petrochemicalhttp://en.wikipedia.org/wiki/Alkylationhttp://en.wikipedia.org/wiki/Butenehttp://en.wikipedia.org/wiki/Butanehttp://en.wikipedia.org/wiki/Octane_ratinghttp://en.wikipedia.org/wiki/Heat_pump


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is the heat moved from the cold reservoir (to the hot reservoir).

is the workconsumed by the heat pump.

Unit of refrigeration

Domestic and commercial refrigerators may be rated in kJ/s, or Btu/h of cooling.

Commercial refrigerators in the US are mostly rated in tons of refrigeration, but

elsewhere in kW. One ton of refrigeration capacity can freeze one short ton of water at 0

C (32 F) in 24 hours. Based on that:

Latent heat of ice (i.e., heat of fusion) = 333.55 kJ/kg 144 Btu/lb

One short ton = 2000 lb

Heat extracted = (2000)(144)/24 hr = 288000 Btu/24 hr = 12000 Btu/hr = 200

Btu/min

1 ton refrigeration = 200 Btu/min = 3.517 kJ/s = 3.517 kW
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METHODS OF REFRIGERATION

Methods of refrigeration can be classified as non-cyclic, cyclic and thermoelectric.

Non-cyclic refrigeration

In these methods, refrigeration can be accomplished by melting ice or by sublimingdry

ice. These methods are used for small-scale refrigeration such as in laboratories and

workshops, or in portable coolers.

Cyclic refrigeration

This consists of a refrigeration cycle, where heat is removed from a low-temperature

space or source and rejected to a high-temperature sink with the help of external work,

and its inverse, the thermodynamic power cycle. In the power cycle, heat is supplied from

a high-temperature source to the engine, part of the heat being used to produce work and

the rest being rejected to a low-temperature sink. This satisfies the thermodynamics. Heat

naturally flows from hot to cold. Workis applied to cool a living space or storage volume

by pumping heat from a lower temperature heat source into a higher temperature heat

sink. Insulation is used to reduce the work and energy required to achieve and maintain a

lower temperature in the cooled space. The operating principle of the refrigeration cycle

was described mathematically by Sadi Carnot in 1824 as a heat engine.
http://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Sublimation_(physics)http://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Coolerhttp://en.wikipedia.org/wiki/Thermodynamic_power_cyclehttp://en.wikipedia.org/wiki/Mechanical_workhttp://en.wikipedia.org/wiki/Thermal_insulationhttp://en.wikipedia.org/wiki/Nicolas_L%C3%A9onard_Sadi_Carnothttp://en.wikipedia.org/wiki/Carnot_heat_enginehttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Sublimation_(physics)http://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Dry_icehttp://en.wikipedia.org/wiki/Coolerhttp://en.wikipedia.org/wiki/Thermodynamic_power_cyclehttp://en.wikipedia.org/wiki/Mechanical_workhttp://en.wikipedia.org/wiki/Thermal_insulationhttp://en.wikipedia.org/wiki/Nicolas_L%C3%A9onard_Sadi_Carnothttp://en.wikipedia.org/wiki/Carnot_heat_engine


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The most common types of refrigeration systems use the reverse-Rankine vapor-

compression refrigeration cycle although absorption heat pumps are used in a minority of

applications.

Cyclic refrigeration can be classified as:

1. Vapor cycle, and

2. Gas cycle

Vapor cycle refrigeration can further be classified as:

1. Vapor compression refrigeration

2. Vapor absorption refrigeration

Vapor-compression cycle

The vapor-compression cycle is used in most household refrigerators as well as in many

large commercial and industrial refrigeration systems. Figure 1 provides a schematic

diagram of the components of a typical vapor-compression refrigeration system.
http://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Absorption_heat_pumphttp://en.wikipedia.org/wiki/Vapor_compression_refrigerationhttp://en.wikipedia.org/wiki/Vapor_absorption_refrigerationhttp://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Vapor-compression_refrigerationhttp://en.wikipedia.org/wiki/Absorption_heat_pumphttp://en.wikipedia.org/wiki/Vapor_compression_refrigerationhttp://en.wikipedia.org/wiki/Vapor_absorption_refrigeration


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The thermodynamics of the cycle can be analyzed on a diagram as shown in Figure 2. In

this cycle, a circulating refrigerant such as Freon enters the compressoras a vapor. From

point 1 to point 2, the vapor is compressed at constant entropy and exits the compressor

superheated. From point 2 to point 3 and on to point 4, the superheated vapor travels

through the condenserwhich first cools and removes the superheat and then condenses

the vapor into a liquid by removing additional heat at constant pressure and temperature.

Between points 4 and 5, the liquid refrigerant goes through the expansion valve (also

called a throttle valve) where its pressure abruptly decreases, causing flash evaporation

and auto-refrigeration of, typically, less than half of the liquid.

That results in a mixture of liquid and vapor at a lower temperature and pressure as

shown at point 5. The cold liquid-vapor mixture then travels through the evaporator coil

or tubes and is completely vaporized by cooling the warm air (from the space being

refrigerated) being blown by a fan across the evaporator coil or tubes. The resulting
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refrigerant vapor returns to the compressor inlet at point 1 to complete the

thermodynamic cycle.

Vapor absorption cycle

In the early years of the twentieth century, the vapor absorption cycle using water-

ammonia systems was popular and widely used. After the development of the vapor

compression cycle, the vapor absorption cycle lost much of its importance because of its

low coefficient of performance (about one fifth of that of the vapor compression cycle).

Today, the vapor absorption cycle is used mainly where fuel for heating is available but

electricity is not, such as in recreational vehicles that carry LP gas. It's also used in

industrial environments where plentiful waste heat overcomes its inefficiency.
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The absorption cycle is similar to the compression cycle, except for the method of raising

the pressure of the refrigerant vapor. In the absorption system, the compressor is replaced

by an absorber which dissolves the refrigerant in a suitable liquid, a liquid pump which

raises the pressure and a generator which, on heat addition, drives off the refrigerant

vapor from the high-pressure liquid. Some work is required by the liquid pump but, for a

given quantity of refrigerant, it is much smaller than needed by the compressor in the

vapor compression cycle. In an absorption refrigerator, a suitable combination of

refrigerant and absorbent is used. The most common combinations are ammonia

(refrigerant) and water (absorber) and water (refrigerant) and lithium bromide (absorber).

Gas refrigeration cycle

When the working fluid is a gas that is compressed and expanded but doesn't change

phase, the refrigeration cycle is called a gas cycle. Airis most often this working fluid.

As there is no condensation and evaporation intended in a gas cycle, components

corresponding to the condenser and evaporator in a vapor compression cycle are the hot

and cold gas-to-gas heat exchangers in gas cycles.
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The gas cycle is less efficient than the vapor compression cycle because the gas cycle

works on the reverse Brayton cycle instead of the reverse Rankine cycle. As such the

working fluid does not receive and reject heat at constant temperature.Because of their

lower efficiency and larger bulk, air cycle coolers are not often used nowadays in

terrestrial cooling devices. The air cycle machine is very common, however, on gas

urbine-powered jet aircraft because compressed air is readily available from the engines'

compressor sections.

Thermoelectric refrigeration

Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of

two different types of materials. This effect is commonly used in camping and portable

coolers and for cooling electronic components and small instruments.
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Magnetic refrigeration

Magnetic refrigeration, or adiabatic demagnetization, is a cooling technology based on

the magnetocaloric effect, an intrinsic property of magnetic solids. The refrigerant is

often aparamagneticsalt, such as cerium magnesiumnitrate. The active magneticdipoles

in this case are those of the electron shells of the paramagnetic atoms.A strong magnetic

field is applied to the refrigerant, forcing its various magnetic dipoles to align and putting

these degrees of freedom of the refrigerant into a state of lowered entropy. A heat sink

then absorbs the heat released by the refrigerant due to its loss of entropy. Thermal

contact with the heat sink is then broken so that the system is insulated, and the magnetic

field is switched off. This increases the heat capacity of the refrigerant, thus decreasing

its temperature below the temperature of the heat sink.

Other methods

Other methods of refrigeration include the air cycle machine used in aircraft; the vortex

tube used for spot cooling, when compressed air is available; and thermo-acoustic

refrigeration using sound waves in a pressurised gas to drive heat transfer and heat

exchange.
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TYPES OF VAPOUR ABSORPTION SYSTEM

Carres process

Absorption cooling was invented by the French scientist Ferdinand Carre in 1858. The

original design used water and sulfuric acid.The expansion device and evaporator used in

this system is similar to the VCR system. Instead of a compressor, an absorber generator

assembly is used with regulation valves and heat exchangers. Pressure is increased in

liquid phase and hence less mechanical work is required. It is a robust technology.


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Einstein refrigerator

The machine is a single-pressure absorption refrigerator, similar in design to a gas

absorption refrigerator. The refrigeration cycle uses ammonia pressure-equalizing fluid,

butane refrigerant, and water absorbing fluid, has no moving parts, and does not require

electricity to operate, needing only a heat source, e.g. a small gas burner or electric

heating element.The ammonia is introduced into the evaporator, causing the refrigerant to

evaporate, taking energy from the surroundings, due to the fact that the partial pressure of

the refrigerant is reduced, and the mix of gasses then passed through to a Condenser heat

transfer condenser where it comes into contact with the absorption liquid. Since ammonia

is soluble in water and butane is insoluble, the ammonia gas is absorbed by the water,

freeing the butane. Heat is thus first given from the butane to the ammonia as the gasses

mix, and then from the ammonia to the water, as the ammonia leaves the butane, taking

heat with it, and dissolves into the water. The butane then assumes the pressure inside the

condenser, which is enough to make it liquefy. Since butane's specific gravity is less than

that of ammonia in solution in water, the liquid butane floats on top of the ammonia

solution. The liquid butane then passes back to the evaporator to repeat the cycle. The


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ammonia solution flows to a heat exchanger where a heat source drives it from the water

as a gas again and it returns to the evaporator. The Einstein refrigerator has been

described as "noiseless, inexpensive to produce and durable".

Lithium bromide Water system

As shown in the figure, the cooling water (which acts as heat sink) flows first to absorber,

extracts heat from absorber and then flows to the condenser for condenser heat extraction.

This is known as series arrangement. This arrangement is advantageous as the required

cooling water flow rate will be small and also by sending the cooling water first to the

absorber, the condenser can be operated at a higher pressure to prevent crystallization. It

is also possible to have cooling water flowing paralleling to condenser and absorber,

however, the cooling water requirement in this case will be high. A refrigerant pump

circulates liquid water in evaporator and the water is sprayed onto evaporator tubes for

good heat and mass transfer. Heater tubes (steam or hot water or hot oil) are immersed in

the strong solution pool of generator for vapour generation. Pressure drops between


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evaporator and absorber and between generator and condenser are minimized, large sized

vapour lines are eliminated and air leakages can also be reduced due to less number of

joints.

ELECTROLUX REFRIGERATION SYSTEM

History

In 1922, two young engineers, Baltzar von Platen and Carl Munters from the Royal

Institute of Technology in Stockholm, submitted a degree project that gained them much

attention. It was a refrigeration machine that employed a simple application of the

absorption process to transform heat to cold. The heat source that initiated the process

could be fueled by electricity, gas or kerosene, making the system extremely flexible.


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The two inventors needed money to develop and market their product, however. By 1923,

they had come as far as establishing two companies, AB Arctic and Platen-Munters

Refrigeration System. Refrigerator production got under way now, albeit on a small

scale, at the new Arctic factory in Motala. The absorption refrigeration machine was far

from fully developed when Wenner-Gren began to take an interest in it. It was, then, a

bold move when he made an offer for the two companies, which meant Electrolux's

future would depend on the success of the refrigerator. In 1925, Electrolux introduced its

first refrigerators on the market. Intense efforts to develop refrigeration technology were

under way at a refrigeration lab that had been set up in Stockholm. The primary goal was

to develop an air-cooled system. Platen-Munters' first appliance was water-cooled and

had to be connected to a heat source, a water line and a drain in order to function. It was a

fairly impractical solution. This was one of the reasons for bringing physicist John

Tandberg to the lab. Tandberg was one of the specialists who played a key role in the

development of refrigeration technology at Electrolux, making contributions to

improving the control of corrosion and rust and much more.


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How it works?

The continuous absorption type of cooling unit is operated by the application of a limited

amount of heat furnished by gas, electricity or kerosene. No moving parts are employed.

The unit consists of four main parts - the boiler, condenser, evaporator and absorber.

The unit can be run on electricity, kerosene or gas. When the unit operates on kerosene or

gas the heat is supplied by a burner which is fitted underneath the central tube (A) and

when the unit operates on electricity the heat is supplied by a heating element inserted in

the pocket (B).The unit charge consists of a quantity of ammonia, water and hydrogen at

a sufficient pressure to condense ammonia at the room temperature for which the unit is

designed. When heat is supplied to the boiler system, bubbles of ammonia gas are

produced which rise and carry with them quantities of weak ammonia solution through

the siphon pump (C). This weak solution passes into the tube (D), whilst the ammonia

vapor passes into the vapor pipe (E) and on to the water separator. Here any water vapor

is condensed and runs back into the boiler system leaving the dry ammonia vapor to pass

to the condenser. Air circulating over the fins of the condenser removes heat from the

ammonia vapor to cause it to condense to liquid ammonia in which state it flows into the

evaporator. The evaporator is supplied with hydrogen. The hydrogen passes across the

surface of the ammonia and lowers the ammonia vapor pressure sufficiently to allow the

liquid ammonia to evaporate. The evaporation of the ammonia extracts heat from the

food storage space, as described above, thereby lowers the temperature inside the

refrigerator. The mixture of ammonia and hydrogen vapor passes from the evaporator to

the absorber. Entering the upper portion of the absorber is a continuous trickle of weak


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ammonia solution fed by gravity from the tube (D). This weak solution, flowing down

through the absorber comes into contact with the mixed ammonia and hydrogen gases

which readily absorbs the ammonia from the mixture, leaving the hydrogen free to rise

through the absorber coil and to return to the evaporator. The hydrogen thus circulates

continuously between the absorber and the evaporator. The strong ammonia solution

produced in the absorber flows down to the absorber vessel and thence to the boiler

system, thus completing the full cycle of operation. The liquid circulation of the unit is

purely gravitational.Heat is generated in the absorber by the process of absorption. This

heat must be dissipated into the surrounding air. Heat must also be dissipated from the

condenser in order to cool the ammonia vapor sufficiently for it to liquefy. Free air

circulation is therefore necessary over the absorber and condenser.The whole unit

operates by the heat applied to the boiler system and it is of paramount importance that

this heat is kept within the necessary limits and is properly applied.

A liquid seal is required at the end of the condenser to prevent the entry of hydrogen gas

into the condenser. Commercial Platen-Munters systems are made of all steel with

welded joints. Additives are added to minimize corrosion and rust formation and also to

improve absorption. Since there are no flared joints and if the quality of the welding is

good, then these systems become extremely rugged and reliable. The Platen-Munters

systems offer low COPs (of the order of 0.1 to 0.4) due to energy requirement in the

bubble pump and also due to losses in the evaporator because of the presence of

hydrogen gas. In addition, since the circulation of fluids inside the system is due to

buoyancy and gravity, the heat and mass transfer coefficients are relatively small, further

reducing the efficiency.


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AMMONIA REFRIGERANT (R717)

HISTORY

Many years ago, the food and beverage industry embraced ammonia refrigeration. The

economic advantages alone made it the refrigerant of choice for cold storage facilities

and food processing facilities as well as the dairy and meatpacking industries. Almost all

of the food on the family breakfast, lunch and dinner table passes through an ammonia

refrigeration facility before reaching your grocery store including fresh fruits and

vegetables, meat, poultry and fish, frozen convenience foods, milk, cheese and ice cream,

and beverages such as soft drinks, beer and wine.

Ammonia was among the early refrigerants used in mechanical systems, and it's the only

one of the early refrigerants to secure a lasting role as a refrigerant. Mechanical

refrigeration was developed in the 1800s based on the principle of vapor compression.

The first practical refrigerating machine using vapor compression was developed in 1834

and by the late 1800s refrigeration systems were being used in breweries and cold storage

warehouses. The basic design of the vapor compressor refrigeration system, using

ammonia as a refrigerant in a closed cycle of evaporation, compression, condensation,

and expansion, has changed very little since the early 1900s.

Ammonia was first used as a refrigerant in the 1850s in France and was applied in the

United States in the 1860s for artificial ice production. The first patents for ammonia

refrigeration machines were filed in the 1870s. By the 1900s, ammonia refrigeration

machines were being commercially installed in block ice, food processing, and chemical


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production facilities. By the 1920s, ammonia refrigeration was being applied to ice rinks.

During the 1930s, air conditioning markets began to develop, first for industrial

applications and then for human comfort. The use of smaller units for domestic

refrigerators increased substantially between 1920 and 1930

Ammonia refrigeration has been the backbone of the cold storage and food processing

industries since the early 1900s. Ammonia refrigeration is the most cost effective and

energy efficient method of processing and storing frozen and unfrozen foods. It is the

workhorse for the post-harvest cooling of fruits and vegetables, the cooling of meat,

poultry, and fish, refrigeration in the beverage industry, particularly for beer and wine,

refrigeration of milk and cheese, and the freezing of ice cream. Practically all fruits,

vegetables, produce and meats, as well as many beverages and juices, pass through at

least one facility that uses an ammonia refrigeration system before reaching our homes.

Ammonia refrigeration is also used in the chemical industry.

PROPERTIES

Ammonia is a colorless gas with a characteristic pungent smell. It is lighter than air, its

density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen

bonding between molecules; the liquid boils at 33.3 C, and solidifies at 77.7 C to

white crystals. Liquid ammonia possesses strong ionizing powers reflecting its high of

22. Liquid ammonia has a very high standard enthalpy change of vaporization

(23.35 kJ/mol, cf. water40.65 kJ/mol, methane 8.19 kJ/mol,phosphine 14.6 kJ/mol) and

can therefore be used in laboratories in non-insulated vessels without additional

refrigeration.
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It is miscible with water. Ammonia in an aqueous solution can be expelled by boiling.

The aqueous solution of ammonia is basic. The maximum concentration of ammonia in

water (a saturated solution) has a density of 0.880 g /cm and is often known as '.880

Ammonia'. Ammonia does not burn readily or sustain combustion, except under narrow

fuel-to-air mixtures of 15-25% air. When mixed with oxygen, it burns with a pale

yellowish-green flame. At high temperature and in the presence of a suitable catalyst,

ammonia is decomposed into its constituent elements. Ignition occurs when chlorine is

passed into ammonia, forming nitrogen and hydrogen chloride; if ammonia is present in

excess, then the highly explosive nitrogen trichloride (NCl3) is also formed.

CHEMICAL PROPERTIES

One of the most characteristic properties of ammonia is its basicity. It combines with

acids to form salts; thus with hydrochloric acid it forms ammonium chloride (sal-

ammoniac); with nitric acid, ammonium nitrate, etc. However, perfectly dry ammonia

will not combine with perfectly dry hydrogen chloride: moisture is necessary to bring

about the reaction.

NH3 + HCl NH4Cl
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The salts produced by the action of ammonia on acids are known as the ammonium salts

and all contain the ammonium ion (NH4+). Anhydrous ammonia is often used for the

production of methamphetamine. Aqueous ammonia can be applied on the skin to lessen

the effects of acidic animal poisons, such as from insect andjellyfish.

Although ammonia is well-known as a base, it can also act as an extremely weak acid. It

is a protic substance and is capable of formation ofamides (which contain the NH2 ion),

for example lithium and ammonia react to give a solution oflithium amide:

2 Li + 2 NH3 2 LiNH2 + H2

Triple point 195.4 K (77.75 C),6.060 kPa

Critical point 405.5 K (132.3 C),11.300 MPa

Std enthalpy change

of fusion, fusHo

+5.653 kJ/mol

Std entropy change

of fusion, fusSo

+28.93 J/(molK)

Std enthalpy change

of vaporization, vapHo

+23.35 kJ/mol at BP of 33.4 C

Std entropychangeof vaporization vapSo , +97.41 J/(molK at BP of 33.4 C

PHYSICAL PROPERTIES
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Anhydrous ammonia is a clear liquid that boils at a temperature of -28F. In refrigeration

systems, the liquid is stored in closed containers under pressure. When the pressure is

released, the liquid evaporates rapidly, generally forming an invisible vapor or gas. The

rapid evaporation causes the temperature of the liquid to drop until it reaches the normal

boiling point of -28F, a similar effect occurs when water evaporates off the skin, thus

cooling it. This is why ammonia is used in refrigeration systems. Liquid anhydrous

ammonia weighs less than water. About eight gallons of ammonia weighs the same as

five gallons of water. Liquid and gas ammonia expand and contract with changes in

pressure and temperature. For example, if liquid anhydrous ammonia is in a partially

filled, closed container it is heated from 0F to 68F, the volume of the liquid will

increase by about 10 percent. If the tank is 90 percent full at 0F, it will become 99

percent full at 68F. At the same time, the pressure in the container will increase from 16

pounds per square inch (psi) to 110 psi.Liquid ammonia will expand by 850 times when

evaporating: Anhydrous ammonia gas is considerably lighter than air and will rise in dry

air. However, because of ammonias tremendous affinity for water, it reacts immediately

with the humidity in the air and may remain close to the ground.

The odor threshold for ammonia is between 5 - 50 parts per million (ppm) of air. The

permissible exposure limit (PEL) is 50 ppm averaged over an 8 hour shift. It is

recommended that if an employee can smell it they ought to back off and determine if

they need to be using respiratory protection.

USES OF AMMONIA


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Cleaner

Household ammonia is a general purpose cleaner that can be used on many surfaces.

Because ammonia results in a relatively streak-free shine, one of its most common uses is

to clean glass, porcelain and stainless steel. It is also frequently used for cleaning ovens

and soaking items to loosen baked-on or caked-on grime.

-As a vehicle fuel

Ammonia has been proposed as a practical alternative to fossil fuel for internal

combustion engines. The calorific value of ammonia is 22.5 MJ/kg (9690 BTU/lb) which

is about half that of diesel. In a normal engine, in which the water vapor is not condensed,

the calorific value of ammonia will be about 21% less than this figure. It can be used in

existing engines with only minor modifications to carburetors/injectors.

To meet these demands, significant capital would be required to increase present

production levels. Although the second most produced chemical, the scale of ammonia

production is a small fraction of world petroleum usage. It could be manufactured from

renewable energy sources, as well as coal or nuclear power. It is however significantly

less efficient than batteries.. If produced from coal, the CO2 can be readily sequestrated.

(the combustion products are nitrogen and water). In 1981 a Canadian company

converted a 1981 Chevrolet Impala to operate using ammonia as fuel.

Hazards of ammonia
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Ammonia is not, strictly speaking, a poison and repeated exposure to it produces no

additive (chronic) effects on the human body. However, even in small concentrations in

the air it can be extremely irritating to the eyes, throat, and breathing passages. Ammonia

is a corrosive, toxic gas with a very pungent odour. It is slightly lighter than air and it can

mix with water vapour and become heavier than air, collecting in pockets at floor level. It

is not normally flammable, but at extremely high concentrations it can create an

explosive mixture with air. Ammonia is a severe irritant of the eyes, nose and throat,

where airborne concentrations between 25 and 50 ppm may be irritating to the mucous

membranes. Exposures in excess of the allowable limit (25ppm) can cause headaches,

coughing and difficulty breathing. Prolonged exposure to high concentrations of

ammonia can lead to pulmonary edema (an accumulation of fluid in the lungs) which can

be fatal. Skin contact with liquid ammonia can cause burns, blisters and even frostbite.

Eye contact can cause severe damage to the eye and may lead to blindness

anhydrous ammonia primarily affects three areas of the body:

Eyes

Lungs

Skin

Eyes

Everything from mild irritation to destruction of the eye can occur depending on whether

a spray or gas is involved. Ammonia penetrates the eye more rapidly than other alkalis.

Lungs


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In the lungs, liquid anhydrous ammonia causes destruction of delicate respiratory tissue.

Exposure to ammonia vapor may cause:

Convulsive coughing.

Difficult or painful breathing.

Pulmonary congestion and death

Gaseous ammonia effects at various concentrations are as follows:

25 ppm or less - TWA

25-50 ppm - Detectable odor; unlikely to experience adverse effects

50-100 ppm - Mild eye, nose, and throat irritation; may develop tolerance in

1-2 weeks with no adverse effects thereafter

140 ppm - Moderate eye irritation; no long-term sequelae in exposures of less

than 2 hours

400 ppm - Moderate throat irritation

500 ppm - IDLH

700 ppm - Immediate eye injury

1000 ppm - Directly caustic to airway

1700 ppm - Laryngospasm

2500 ppm - Fatality (after half-hour exposure)

2500-6500 ppm - Sloughing and necrosis of airway mucosa, chest pain,

pulmonary edema, and bronchospasm


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Skin

Skin damage depends upon the length and concentration of exposure and can range from

mild irritation, to a darkened freeze-dry burn, to tissue destruction. Because liquid

ammonia boils at -28F, the expanding gas has the potential to freeze anything in its path

of release, including human flesh and organs. Because water can absorb ammonia so

readily, it is a factor that contributes to human toxicity. Ammonia will keep spreading

across contacted skin until the chemical is diluted bys kin moisture. Alkalis effect tissue

differently than acids, which tend to burn and seal off a wound. Alkalis, such as ammonia

cause liquidization of tissue and turn tissue into a sticky "goo" and mix with this tissue,

causing further damage. As a result, anhydrous ammonia burns keep spreading until the

chemical is diluted. In addition to liquidization, super-cooled anhydrous ammonia spray

causes a freeze dry effect like frost bite when it hits the skin. The spray is also capable of

freezing clothing to skin so that if the clothing is removed incorrectly whole sections of

skin can be torn off. High concentrations in the air can also dissolve in the moisture of the

skin or perspiration and result in a corrosive action on the skin and mucous membranes.

ACCIDENTS

A number of accidental releases of ammonia have occurred from refrigeration facilities in

the past. Causes of these releases include plant upsets, leading to the lifting of relief

valves; leaks in rotating seals; pipeline failures; vehicular traffic hitting pipes, valves, and

evaporators; and failures during ammonia delivery, such as hose leaks. Some of these

releases have killed and injured workers, caused injuries off site, or resulted in

evacuations. The following describes several recent incidents in more detail. A specific


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incident demonstrates the need for mechanical protection to protect refrigeration

equipment from impact. In a 1992 incident at a meat packing plant, a forklift struck and

ruptured pipe carrying ammonia for refrigeration. Workers were evacuated when the leak

was detected. A short time later, an explosion occurred that caused extensive damage,

including large holes in two sides of the building. The forklift was believed to be the

source of ignition. In this incident, physical barriers would have provided mechanical

protection to the refrigeration system and prevented a release.

HAZARD AWARENESS

Ammonia is used widely and in large quantities for a variety of purposes. More than 80%

of ammonia produced is used for agricultural purposes; less than two percent is used for

refrigeration. Use of ammonia is generally safe provided appropriate maintenance and

operating controls are exercised. It is important to recognize, however, that ammonia is

toxic and can be a hazard to human health. It may be harmful if inhaled at high

concentrations. The Occupational Safety and Health Administration (OSHA) Permissible

Exposure Level (PEL) is 50 parts per million (ppm), 8-hour time-weighted average.

Effects of inhalation of ammonia range from irritation to severe respiratory injuries, with

possible fatality at higher concentrations. The National Institute of

Occupational Safety and Health (NIOSH) has established an Immediately Dangerous to

Life and Health (IDLH) level of 300 ppm for the purposes of respirator selection.

Ammonia is corrosive and can burn the skin and eyes. Liquefied ammonia can

cause frostbite.


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WATER ABSORBENT

Properties and existence

Water (H2O, HOH) is the most abundant molecule on Earth's surface, constituting about

75% of the Earth's surface in liquid, solid, and gaseous states. It is in dynamic

equilibrium between the liquid and gas states at standard temperature and pressure. At

room temperature, it is a nearly colorless (with a hint of blue), tasteless, and odorless

liquid. Many substances dissolve in water and it is commonly referred to as the universal

solvent. Water is the chemical substance with chemical formula H2O: one molecule of

water has two hydrogenatomscovalentlybonded to a single oxygen atom. Water is a

tasteless, odorless liquid at ambient temperature and pressure, and appears colorless in

small quantities, although it has its own intrinsic very light blue hue. Ice also appears

colorless, and water vapor is essentially invisible as a gas

Water has the second highest specific heat capacity of any known chemical compound,

afterammonia, as well as a high heat of vaporization (40.65 kJ mol1), both of which are

a result of the extensive hydrogen bonding between its molecules. These two unusual

properties allow water to moderate Earth's climate by buffering large fluctuations in

temperature.

The specific enthalpy of fusion of water is 333.55 kJ kg1 at 0 C. Of common

substances, only that of ammonia is higher. This property confers resistance to melting

upon the ice ofglaciers and drift ice. Before the advent of mechanical refrigeration, ice

was in common use to retard food spoilage.
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One molecule of water has two hydrogenatomscovalentlybonded to a single oxygen

atom. Water is a tasteless, odorless liquid at ambient temperature and pressure, and

appears colorless in small quantities, although it has its own intrinsic very light blue hue.

Ice also appears colorless, and water vapor is essentially invisible as a gas. Water is

primarily a liquid under standard conditions, which is not predicted from its relationship

to other analogous hydrides of the oxygen family in theperiodic table, which are gases

such as hydrogen sulfide. Also the elements surrounding oxygen in the periodic table,

nitrogen, fluorine,phosphorus, sulfurand chlorine, all combine with hydrogen to produce

gases under standard conditions. The reason that water forms a liquid is that it is more

electronegative than all of these elements (other than fluorine). Oxygen attracts electrons

much more strongly than hydrogen, resulting in a net positive charge on the hydrogen

atoms, and a net negative charge on the oxygen atom. The presence of a charge on each

of these atoms gives each water molecule a net dipole moment. Electrical attraction

between water molecules due to this dipole pulls individual molecules closer together,

making it more difficult to separate the molecules and therefore raising the boiling point.

This attraction is known as hydrogen bonding. The molecules of water are constantly

moving in relation to each other, and the hydrogen bonds are continually breaking and

reforming at the timescales faster than 200 femtoseconds. However, this bond is strong

enough to create many of the peculiar properties of water described in this article, such as

the ones that make it integral to life. Water can be described as apolarliquid that slightly

dissociates disproportionately into the hydronium ion (H3O+

(aq)) and an associated

hydroxide ion (OH(aq)).

2 H2O (l) H3O+

(aq) + OH

(aq)
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Why water?

The polarity of NH3 molecules and their ability to form hydrogen bonds explains to some

extent the high solubility of ammonia in water. However, a chemical reaction also occurs

when ammonia dissolves in water. In aqueous solution, ammonia acts as a base, acquiring

hydrogen ions from H2O to yield ammonium and hydroxide ions.

NH3(aq) + H2O(l) NH4 +(aq) + OHG(aq)

The production of hydroxide ions when ammonia dissolves in water gives aqueous

solutions of ammonia their characteristic alkaline (basic) properties. The double arrow in

the equation indicates that equilibrium is established between dissolved ammonia gas and

ammonium ions. Not all of the dissolved ammonia reacts with water to form ammonium

ions. A substantial fraction remains in the molecular form in solution. Water boils at 273

kelvin at 1 bar atmospheric pressure.

Ammonia is readily miscible in water. Ammonium Hydroxide on slight heating easily

liberates ammonia gas. Water is easily available, safe to handle and environmentally

friendly. Circulation of the solution of water is easy when compared to other phases of

matter. The reaction of ammonia with water is exothermic and the energy from this

exothermic reaction is used for the circulation of hydrogen in the system. All these

properties make it apt to be used as the absorber in our refrigeration system.


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HYDROGEN THE CARRIER GAS

Properties and existence

Hydrogen is the most abundant element in the universe, making up 75% ofnormal matter

by mass and over 90% by number of atoms. This element is found in great abundance in

stars and gas giant planets. Molecular clouds of H2 are associated with star formation.

Hydrogen plays a vital role in powering stars throughproton-proton reaction and CNO

cycle nuclear fusion.

Throughout the universe, hydrogen is mostly found in the atomic and plasma states

whose properties are quite different from molecular hydrogen. As a plasma, hydrogen's

electron and proton are not bound together, resulting in very high electrical conductivity

and high emissivity (producing the light from the sun and other stars). The charged

particles are highly influenced by magnetic and electric fields. For example, in the solar

wind they interact with the Earth's magnetosphere giving rise to Birkeland currents and

the aurora. Hydrogen is found in the neutral atomic state in the Interstellar medium.

Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H2

.However, hydrogen gas is very rare in the Earth's atmosphere (1 ppm by volume)

because of its light weight, which enables it to escape from Earth's gravity more easily

than heavier gases. However, hydrogen (in chemically combined form) is the third most

abundant element on the Earth's surface. Most of the Earth's hydrogen is in the form of

chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by
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