study of a refrigeration unit
TRANSCRIPT
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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