Evaporator Capacity vs. Compressor Capacity
In refrigeration systems, it is essential to understand the difference between evaporator capacity and compressor capacity, as these concepts are fundamental for proper equipment sizing.
Net Refrigeration Effect (Evaporator Capacity)
The Net Refrigeration Effect, also known as evaporator capacity, represents the actual cooling performed at the evaporator. This value should be used to size the compressor to match evaporator load.
Calculation **Evaporator Capacity = Difference in Enthalpies Between States 2 and 3 (Btu/lb)**
- In the Pressure-Enthalpy diagram:
- State 2: Expansion device outlet / evaporator inlet
- State 3: Evaporator outlet (saturated vapor)
Compressor Capacity
Compressor capacity reflects the total capacity of the compressor at selected condition. This capacity includes the work done to offset heat gained in the suction line. Since this superheat does not benefit the cooling of the product, it is typically referred to as non-useful superheat.
Calculation **Compressor Capacity = Difference in Enthalpies Between States 2 and 4 (Btu/lb)**
Compressor Power
Compressor Power = Difference in Enthalpies Between States 4 and 5 (Btu/lb)
Condenser Heat Rejection
Condenser Heat Rejection = Difference in Enthalpies Between States 5 and 1 (Btu/lb)
Summary Table
| Parameter | Formula | Unit |
|---|---|---|
| Evaporator Capacity | h3 - h2 | Btu/lb |
| Compressor Capacity | h4 - h2 | Btu/lb |
| Compressor Power | h5 - h4 | Btu/lb |
| Heat Rejection | h5 - h1 | Btu/lb |