How to Size a Liquid Chiller

 

It should be noted that Opti Temp will size the appropriate liquid chiller for your application and takes no legal responsibility if the customer calculates the specific chiller load, and orders a unit without consultation with Opti Temp. The optimum chiller size needed is based on the amount of heat your application is generating, plus additional power to maintain temperature under varying loads.

Normally the manufacturer of the device you are cooling will supply heat removal information. If information isn't available you can use one of the two calculation methods shown below to correctly size a chiller for your application.

How Much Cooling Capacity Should I Purchase?

Opti Temp liquid chillers use their patented ARCC control (Advanced Refrigeration Capacity Control) circuitry providing for no load to full load capacity control without cycling the compressor.  Most other chiller manufacturers cycle the compressor at less than 50% load, which causes increased wear on the compressor and temperature instability. You are then able to purchase a chiller for more heat removal capacity than the minimal required and thus have future expansion for load increase.

Method A
Watts = [(DT) °F x K] / S
Where

  • DT= the °F difference between incoming and outgoing tap water temperature of your instrument.
    Measure carefully using the same thermometer for both locations.
  • K = Specific heat multiplied by the density of the fluid being circulated.
  • Use 2,326 for water when calculating load in °F
  • Use 1,837 for 50/50 mixture of ethylene glycol and water when calculating load in °F
  • S = the number of seconds to fill a one liter container.

Method B
BTU/Hr=GPM x (DT) °F x 500
Where

  • GPM of process fluid to be circulated
  • DT= the °F difference between incoming and outgoing tap water temperature of your instrument.
    Measure carefully using the same thermometer for both locations.
  • Fluid factor for 100% water=500

Additional Considerations when sizing a liquid chiller

  • If ambient temperature of the cooling location is above 68°F, add 1% to the calculated wattage for each 1.0°F above 68°F.
  • If operating at 50Hz, add 17% to the calculated wattage.
  • If line voltage is consistently below rated voltage, or if you work at high altitude, add 10% to the calculated wattage.
  • Future growth cooling needs or variability of heat output of existing unit.
  • When using a 50/50 mixture of ethylene glycol and water, de-rate the cooling capacity of the
    Chiller by approximately 4%.

Conversions

1kW=3412 BTU/Hr
Tons = (BTU's / hr) / 12,000

Chiller or Heat exchanger sizing calculations

In general, consult the factory when determining the model number for a liquid heat exchanger or liquid chiller. In addition, consult the factory when specifying a chiller with glycol or any fluid other than water.