Summary of calculation methods for key operating parameters of chillers

1. Evaporator small temperature difference: used to evaluate the heat exchange efficiency of the unit evaporator, with a normal value between 1 ℃ and 3 ℃.
Evaporator small temperature difference=outlet temperature of chilled water - saturation temperature corresponding to evaporation pressure
Note: The saturation temperature corresponding to the outlet temperature and evaporation pressure of chilled water is in degrees Celsius (℃);

2. Small temperature difference in the condenser: used to evaluate the heat exchange efficiency of the unit's condenser, with a normal value between 1 ℃ and 3 ℃.
Small temperature difference in condenser=saturation temperature corresponding to condensation pressure - outlet temperature of cooling water
Note: The saturation temperature and cooling water outlet temperature corresponding to condensation pressure are in degrees Celsius (℃)

3. Inhalation superheat degree: used to evaluate parameters such as refrigerant charging amount, supply valve adjustment, and evaporator heat exchange effect. The normal value of a full liquid evaporator is between 1 ℃ and 1.5 ℃; The normal value of a dry evaporator is between 8 ℃ and 12 ℃.
Suction superheat=compressor suction temperature - saturation temperature corresponding to suction pressure
The saturation temperature corresponding to the suction temperature and suction pressure of the compressor is measured in degrees Celsius (℃)

4. Exhaust superheat: used to evaluate parameters such as refrigerant charge and compressor operation status. The normal value of R-22 refrigerant is between 14 ℃ and 19 ℃; The normal value of R-134a refrigerant is between 7 ℃ and 10 ℃.
Exhaust superheat=compressor exhaust temperature - saturation temperature corresponding to exhaust pressure
The saturation temperature corresponding to the discharge temperature and pressure of the compressor is expressed in degrees Celsius (℃)

5. Supercooling degree: used to evaluate parameters such as refrigerant charging amount, supply valve adjustment, and condenser level control. The normal value of a water-cooled condenser with a subcooler is around 5 ℃.
Supercooling degree=saturation temperature corresponding to condensation pressure - condenser outlet temperature
The saturation temperature corresponding to condensation pressure and the outlet temperature of the condenser are measured in degrees Celsius (℃)

6. The presence of non condensable gases: The presence of non condensable gases in the system can be obtained, and the normal value should be less than 3 ℃.
Existence degree of non condensable gas=saturation temperature corresponding to condensation pressure - condenser outlet temperature
The saturation temperature corresponding to condensation pressure and the outlet temperature of the condenser are measured in degrees Celsius (℃)

7. Unit operating efficiency: The unit operating efficiency is used to evaluate the operating efficiency of the unit.
KW/cold ton=input power/unit cooling capacity
The unit of input power is kilowatt (kW); The unit of refrigeration capacity of the unit is cold tons (RT);
COP=unit cooling capacity/input power;
The unit of refrigeration capacity and input power of the unit should be unified (kW or RT) COP X kW/cold ton=3.516

8. Calculation method for cooling capacity and condensation capacity:
Refrigeration capacity=chilled water flow rate X temperature difference between chilled water inlet and outlet/24
The unit of chilled water flow is gallons per minute (GPM); The temperature difference between the inlet and outlet of chilled water is measured in degrees Fahrenheit (℉)
Condensation rate=cooling water flow rate X temperature difference between cooling water inlet and outlet/24
The unit of cooling water flow is gallons per minute (GPM); The temperature difference between the inlet and outlet of cooling water is measured in degrees Fahrenheit (℉)

Source: Zhihu - Refrigeration and Air Conditioning Technology