Study of a Refrigeration UnitPresented By-Abdullah Al Masud (1202019)

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Objectives

To study vapor compression refrigeration cycle with visual observations

To investigate the saturation pressure-temperature relationship during evaporation and condensation

To determine the effect of compressor pressure ratio on system performance

To Determine of the effect of evaporating and condensing temperatures on the refrigeration rate and condenser heat output

To Determine of the overall heat transfer between R141 b and water in the evaporator and condenser

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Theory

Refrigeration is a process of transformation heat from a

lower temperature region to higher one.

The coefficient of performance of a refrigerator is expressed

as COP

COP = =

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Theory (continued)

Vapor-Compression Refrigeration Cycle

(a) Schematic (b) T-s diagram 12/19/2015

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Theory (continued)

Actual Vapor-Compression Refrigeration Cycle

(a) Schematic (b) T-s diagram12/19/2015

Experimental Setup

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Observed DataObservation No 1 2 3 4 5

Evaporator Gauge Pressure,Pe (KN/m2 ) -62 -65 -68 -68 -65

Absolute Evaporator Pressure, Pe (KN/m2 ) 39.378 36.378 33.325

 

33.325

 

36.378

Evaporator temperature,t5( oC) 11 10 9.8 10.5 11.5

Evaporator water flow rate, me (g/s) 4 4 4 4 4

Evaporator water inlet temperature,t1( oC) 16 15.2 15.2 16 17

Evaporator water outlet temperature,t2( oC) 12 10 10 10 11

Condensed liquid temperature, t8( oC) 26.2 28 29.8 30.4 32

Condensed gauge pressure, pc (KN/m2 ) 120 130 138 141 149

Absolute condenser pressure, pc (KN/m2 ) 221.378 221.378 221.378 221.378 221.378

Compressor discharge temperature,t7( oC) 52 54 55 56 56

Condenser temperature,t6( oC) 26 28 30 31 32

Condenser water flow rate,mc (g/s) 28 24 20 16 12

Condenser water inlet temperature,t4( oC) 14.5 15 15 16 16.5

Condenser water outlet temperature,t3( oC) 15 16.5 17 18.5 20

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Sample Calculation

Actual pressure• Absolute pressure

of evaporator, Pe=pe+P

• absolute pressure of Condeser, Pc=pc+P

Compressor pressure ratio

=

Calculation of rate of Heat transfer

Rate of heat transfer =mCpΔt

Calculation of Overall heat

transfer coefficient

Ue = QeAe ∆TLMTD (evaporator )

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Sample Calculation ( Continued)

Here,ΔTLMTD =

Tin=temperature difference between water inlet and R141b Tout= temperature difference between water outlet and R141b For evaporator, Tin=t1-t5 , Tout= t2-t5

For condenser, Tin=t6-t4 , Tout= t6-t3

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Experimental Outcomes Experimental and therotetical saturation pressure vs. saturation temperature curve for both evaporator and condenser.

Experimental Theoretical12/19/2015 10

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Experimental Outcomes (continued)

Experimental and theoretical curve for rate of heat transfer vs. condensing temperature

Experimental Theoretical 12/19/2015

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Experimental Outcomes (continued)

Exeprimetal and theoretical curve for rate of heat transfer vs. compressor pressure ratio

Experimental Theoretical 12/19/2015

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Experimental Outcomes (continued)

No of obs

Heat transfer

rate,QCompressor

Pressure ratio,r

Overall heat transfer

co-efficient,U

Evaporator, Qe

(kN/m2)

Condenser, Qc

(kN/m2)

Evaporator,

Ue (W/m2.C)

Condenser, Uc

(W/m2.C)

1 66.880 58.520 5.622 839.360 162.582

2 86.944 150.480 6.360 1223.500 384.358

3 86.944 167.200 7.172 1719.600 373.851

Results

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Deviation and clarification

Experimental results fluctuate from the theoretical ones because of some reasons. Some of them are discussed below :

System was not perfectly insulated and refrigerant exchanged heat with the surroundings

Introduction of huge source of pressure drop by valves.

The system must be fed with an accurate charge of refrigerant

The system must be air free.

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Why we use refrigeration system?

Food preservation

Air conditioning system

Compressed air purification

In chemical plants

Reduction of moisture content

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Thank you!The End

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