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CONTENTS

1.INTRODUCTION

2.MOTIVATION AND ADVANTAGES

3.OBJECTIVE

4.TECHNICAL DETAILS

5.COMPRESSORLESS REFRIGERATION UNIT

6.TYPES OF REFRIGERANTS USED

7.COP OF REFRIGERATOR AND ITS VARIATIONS

8.PROBLEMS AND PRESENT DAY NEED

INTRODUCTION

1.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.

2.The primary purpose of refrigeration is lowering the temperature of the

enclosed space or substance and then maintaining that lower temperature.

3.There are mainly two refrigeration cycles namely:vapor compression and

vapour absorption.

4.In case of compression cycle the suction and compression work of the

refrigerant is done with the help of a compressor.

5.the same in absorption cycle is done with the help of an absorber and a

generator.

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MOTIVATION

1.The absorption refrigeration system is used mainly where fuel for heating is available

but electricity is not.

2.It can be used at remote places as it can work even with a simple kerosene lamp thoughin small capacity.

ADVANTAGES:

1.Uses low grade energy like heat

2.Smooth operation because moving parts are only in the pump, which is a small elementof the system.

3.No effect of reducing the load on performance

4.Liquid traces of refrigerant present in piping at the exit of evaporator constitute no

danger.

5.Less cost and maintenace required.

OBJECTIVE

1.To develop a compressorless refrigeration system model based on vapour absorption

cycle which will work on low grade energy resource.

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2.In remote areas where high grade energy(electricity) is not available in abundance and

people are more dependent on natural byproducts like plant wastes,cowdung etc.,the

proposed system offers a way for conservation of non renewable resources unlike

conventional refrigeration systems which work on the same principle of vapour

absorption cycle.

TECHNICAL DETAILS

WORKING:

1.Ammonia vapour is produced in the generator at high pressure from the strong solution

of NH3 by an external heating source.

2.The water vapour carried with ammonia is removed in the rectifier and only the

dehydrated ammonia gas enters into the condenser.

3. High pressure NH3 vapour is condensed in the condenser. The cooled NH3 solution is

passed through a throttle valve and the pressure and temperature of the refrigerant are

reduced below the temperature to be maintained in the evaporator.

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4. The low temperature refrigerant enters the evaporator and absorbs the required heat

from the evaporator and leaves the evaporator as saturated vapour.

5.Weak NH3 solution (aquaammonia) entering the absorber becomes strong solution

after absorbing NH3 vapour and then it is pumped to the generator through the heat

exchanger. The pump increases the pressure of the strong solution to generator pressure.

6.The weak high temperature ammonia solution from the generator is passed to the heat

exchanger through the throttle valve. The pressure of the liquid is reduced to the absorberpressure by the throttle valve.

COMPRESSORLESS REFRIGERATION UNIT:

TYPES OF REFRIGERANTS USED:

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1.Fluid mixtures are used in these systems,out of which one acts as refrigerant and the

other as its solvent.

2.Some commonly used mixtures are:ammonia-water,ammonia-hydrogen(in domestic

elecrolux refrigerators),lithium-bromide,etc

3.some under investigation mixtures are:

a)R-22 and dimethylether of tetra ethylene gycol

b)R-22 and isobutyl acetatec)R-22 and dimethyl formide

absorption cycle based on li-br:

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COP OF REFRIGERATOR AND ITS VARIATIONS

COP = REFRIGERATING EFFECT/WORK INPUT

=(Q2)/(Q1-Q2)

WHERE,

Q1=HEAT REJECTED TO THE SINK

Q2=HEAT ABSORBED FROM SPACE TO BE COOLED

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PROBLEMS AND PRESENT DAY NEED

DISADVANTAGES:

1.Vapour absorption systems are bulky.

2.These system have a low coefficient of performance.

3.Charging of refrigerant in these systems is difficult.

PRESENT DAY NEED:

1.These systems need to be made more compact in order to comply the problems

confronted during handling due to bulkiness.

2.COP needs to be increased.