Calculating chiller and cooling tower refrigeration in tons
Cooling towers tons pairs the water-cooled chiller tons and the water-cooled condenser tons.
Chiller Refrigeration Tons
A water-chiller refrigeration ton is defined as:
1 refrigeration ton = 1 TONScond = 12,000 Btu/h = 3,025.9 k Calories/h = 12,661 kJ/h
A ton is the amount of heat removed by an air conditioning system that would melt 1 ton (2000 lbs.) of ice in 24 hours:
288,000 BTU/24 hr = 12,000 BTU/hr
Converting Btu to Tons of Refrigeration
| Btu per hour | Tons of Refrigeration |
| 6000 | 1/2 |
| 12000 | 1 |
| 18000 | 1 1/2 |
| 24000 | 2 |
| 30000 | 2 1/2 |
| 36000 | 3 |
| 42000 | 3 1/2 |
| 48000 | 4 |
| 54000 | 4 1/2 |
| 60000 | 5 |
Cooling Tower Tons
A cooling tower ton is defined as:
1 cooling tower ton = 1 TONSevap = 1 TONScond x 1.25 = 15,000 Btu/h = 3,782 k Calories/h = 15,826 kJ/h
The equivalent ton on the cooling tower side actually rejects about 15,000 Btu/h due to the heat-equivalent of the energy needed to drive the chiller's compressor. This equivalent ton is defined as the heat rejection in cooling 3 U.S. gallons/minute (1,500 pound/hour) of water 10°F, which amounts to 15,000 Btu/hour, or a chiller coefficient-of-performance (COP) of 4.0 - a COP equivalent to an energy efficiency ratio (EER) of 13.65.
Heat Load and Water Flow
A water systems heat load in Btu/h can be simplified to:
h = cp ρ q dt
= (1 Btu/lbm oF) (8.33 lbm/gal) q (60 min/h) dt
= 500 q dt (1)
where
h = heat load (Btu/h)
cp = 1 (Btu/lbm oF) for water
ρ = 8.33 (lbm/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 10oF temperature difference. The ton of cooling load can be calculated as:
Cooling load = 500 (1 gal/min) (10 oF) / 12,000
= 0.42 ton