1. Mohamed Iqbal Pallipurath
Refrigeration Cycles
Mohamed Iqbal Pallipurath

2. Refrigerators and Heat Pumps
Refrigerators: move heat from colder space
Heat pump: move heat to warmer space
Both require work input

3. Refrigerators and Heat Pumps
Performance is expressed in term of coefficients of performance

4. Carnot Cycle Model
Reverse Carnot Cycle

5. Reverse Carnot Cycle
Coefficients of performance for Carnot cycles can be expressed in terms of temperature

6. Ideal Vapor-Compression Refrigeration Cycle
1-2 Isentropic compression in compressor
2-3 Constant-pressure heat rejection in a condenser
3-4 Throttling in an expansion valve (irreversible process)
4-1 Constant-pressure heat absorption in an evaporator

7. Ideal Vapor-Compression Refrigeration Cycle Analysis
Steady-flow
Where h1 = and h3 =

12. Actual Vapor-Compression Cycle
Differences
Evaporator discharge
Higher specific volume in compressor
Compressor losses
Condenser pressure losses

18. What Refrigerant? Types: Chlorofluorocarbons (CFCs) Ammonia
Hydrocarbons (propane, ethane, ethylene, etc.)
Carbon dioxide

19. What Refrigerant? Driving criteria:
Temperatures of where heat is removed from and where it is moved to.

20. Heat Pumps Reverse of refrigerators
Bring heat from lower temperature space to higher temperature space.
Energy source
Air
Water/soil

21. Gas Refrigeration Cycle

22. Gas Refrigeration Cycle
Fluid always a gas, no phase change
Lower COP than vapor-compression systems
Used in aircraft and gas liquefaction