Refrigeration System

Objective:

To study the variation of the operating characteristics of the system (C.O.P., refrigeration effect and compressor work) with compressor speed.

Theory:

1. Refrigerating effect QL = mr (h1-h4)
   
2. Compressor work Wc = mr (h2-h1)      {assuming adiabatic}
   
3. Condenser duty QH = mr (h2-h3)
   
4. C.O.P. = QL/Wc = (h1-h4)/(h2-h1)
   
5. Compressor work = torque*speed
   
6. Condenser duty = mw*Cpw*∆Tw
   
7. Refrigerating effect = VI
   

Conclusion:

1. The effect on C.O.P. is decreasing when increasing the speed and causing the enthalpy of the compressor to increase.
   
2. The refrigeration capacity, the compressor power and the heat rejected in the condenser will increase by increasing the speed of the compressor.
   
3. The maximum enthalpy is the one of the compressor, when the heat transfer to the surrounding is maximum.
   
4. The heat rejected in the condenser is maximum.
   
5. The assumption of ideal cycle neglects the heat transfer to and from the surroundings, which affect the enthalpy of the system and it neglects the irreversibility.
   
6. The C.O.P. also indicates the efficiency of the machine where it relates the output power in the condenser to the input power in the compressor.