Typical Water Flow Rates

Condenser Heat Rejection is 15,000 Btu/h:

Water cooled condenser ratings: ARI Standard 450

Water Temperature, Entering Condenser: 85 °F

Water Temperature, Leaving Condenser: 95 °F

One (1) gallon of water weighs approximately 8.333 lb. If we recirculate one (1) gallon of water per minute we get:

Mass Flow Rate = 1 gal/min * 8.333 lb water/gal water * 60 min/1 h = 500 lb/h

Cooling Tower Ton (Btu/h) = Flow Rate (gal/min) * 500 Btu/h * Delta T (°F)

If we substitute we get:

15,000 Btu/h = Flow Rate (gal/min) * 500 Btu/h * 10 °F

and the flow rate (gal/min) equals 3.

Now for the evaporator we substitute 12,000 Btu/h for the heat rejection and the flow rate is now 2.4 gal/min.

Refrigeration Ton: 15,000 Btu/h

Condenser Heat Rejection Ton: 12,000 Btu/h

Why is there a 3,000 Btu/h difference? This comes mostly from the heat of compression of the refrigerant in the compressor.