Enter the chilled water leaving temperature and the evaporator refrigerant temperature into the calculator to determine the chiller approach temperature.

Approach Temperature Calculators

Pick a scenario, enter the two temperatures, and click Calculate.

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Chiller Approach Temperature Formula

The following formula is used to calculate the chiller approach temperature for a given chilled water leaving temperature and evaporator refrigerant temperature.

AT = T_{cw} - T_{ev}

Variables:

  • AT is the chiller approach temperature
  • Tcw is the chilled water leaving temperature
  • Tev is the evaporator refrigerant temperature

To calculate the chiller approach temperature, subtract the evaporator refrigerant temperature from the chilled water leaving temperature.

What is a Chiller Approach Temperature?

The chiller approach temperature is the difference between the temperature of the chilled water leaving the chiller and the temperature of the refrigerant inside the evaporator. This temperature difference is an important parameter in assessing the performance and efficiency of a chiller system. A lower approach temperature indicates a more efficient heat transfer process, while a higher approach temperature may suggest issues such as fouling, scaling, or other inefficiencies within the chiller system.

How to Calculate Chiller Approach Temperature?

The following steps outline how to calculate the Chiller Approach Temperature.


  1. First, determine the chilled water leaving temperature (Tcw).
  2. Next, determine the evaporator refrigerant temperature (Tev).
  3. Finally, calculate the chiller approach temperature using the formula AT = Tcw - Tev.
  4. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Chilled Water Leaving Temperature (Tcw) = 7°C

Evaporator Refrigerant Temperature (Tev) = 2°C