Calculating Cooling Loads

Calculating chiller and cooling tower refrigeration in tons

Chiller Refrigeration Tons

A chiller refrigeration ton is defined as:

    1 refrigeration ton = 12,000 Btu/h = 3,025.9 k Calories/h

A ton is the amount of heat removed by an air conditioning system that would melt 1 ton of ice in 24 hours.

Cooling Tower Tons

A cooling tower ton is defined as:

    1 cooling tower ton = 15,000 Btu/h = 3,782 k Calories/h

Heat Load and Water Flow

A water systems heat load in Btu/h can be simplified to:

h = c_p ρ q dt

    = 1 (Btu/lb_m ^oF) 8.33 (lb_m/gal) q (gal/min) 60 (min/h) dt (^oF)

    = 500 q dt (1)

where

h = heat load (Btu/h)

c_p = 1 (Btu/lb_m ^oF) for water

ρ = 8.33 (lb_m/gal) for water

q = water volume flow rate (gal/min)

dt = temperature difference (^oF)

Example - Water Chiller Cooling

Water flows with 1 gal/min and 10^oF temperature difference. The ton of cooling load can be calculated as:

Cooling load = 500 (1 gal/min) (10^oF) / 12,000

= 0.42 ton

• Converting between heat and energy units
• Converting kW/tonn to COP or EER

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