Typically, the manufacturer of your system will know how much heat is needed to be removed from the relevant location in order to operate safely and efficiently. If you need to size a chiller for a new application, however, here are some suggestions:
Terminology:
Watts = [(ΔT)°F x K] / S
Where:

  • ΔT = Temperature variance between incoming and outgoing water temperature of instrument. (It is recommended to use the same sensing device for both measurements.)
  • K = Specific heat x density of the circulating fluid. (Water – Use 2,326 if calculating load in °F / Use 1,837 for 50/50 ratio of ethylene glycol and water if calculating load in °F)
  • S = Time (in seconds) it takes to fill one (1) liter container

BTU/Hr = GPM x (ΔT°F) x 500
Where:

  • GPM of circulating process fluid
  • ΔT = Temperature variance between incoming and outgoing water temperature of instrument. (It is recommended to use the same sensing device for both measurements.)
  • 100% Water fluid factor = 500
  • (1kW = 3,412 BTU/Hr)

kW = LPM x (ΔT°C) / 14.4
Where:

  • LPM of circulating process fluid
  • ΔT = Temperature variance between incoming and outgoing water temperature of instrument. (It is recommended to use the same sensing device for both measurements.)

If you just need a rough number, simply calculate the system’s total power consumption (kW), and approximate the efficiency of your process, i.e. the amount of energy (heat) required to be removed by the chiller.

When in doubt, contact the equipment manufacturer or your technical field sales representative for help in specifying the correct recirculating chiller for your specific application.
This post was authored by Jim White of IES Technical Sales.
IES Technical Sales is the northeast U.S. distributor for Applied Thermal Control, manufacturers of closed loop recirculating chillers from 0.5 to 9kW.