In HVAC and refrigeration industries, the cooling capacity of a refrigeration system (i.e., rate of heat removal from the refrigerated space) is often expressed by the term “Ton of Refrigeration,” which is shortly abbreviated to TR.
DEFINITION OF TR:
1 Ton of Refrigeration (TR) is equal to the rate of heat energy needed to melt 1 Ton (2000 lb, which is equal to 907.184 kg) of pure Ice, at 32 OF (0 OC), to water in 24 hours (i.e., in a day).
Alternate definition: The capacity of a refrigeration system that can freeze 1 ton (2000 lb, which is equal to 907.184 kg) of pure liquid water at 32 OF (0 OC) into ice at 32 OF (0 OC) in 24 hours is said to be 1 Ton of Refrigeration.
EXPLANATION:
Refer to the below picture for the equivalent value of 1 TR in IP and SI system of units. Note that, as per the definition, these values are heat rate and not work rate.
| TON OF REFRIGERATION (TR) |
Refer to the below table for the mass conversion between different systems of unit and latent heat of fusion/melting of pure ice.
| Sl. No | Item | IP Unit | SI Unit | Remarks |
| 1 | Mass (1 Ton) = | 2000 lb. | *907.184 kg | 1 pound (lb) = 0.453592 kg |
| 2 | Latent heat of fusion / melting = | 144 BTU/lb. | 335 kJ/kg | |
| *Note the difference between Ton and Tonne. Ton is imperial (1 Ton = 2000 lb.), Tonne is metric (1 Tonne = 1000 kg = 2204.62 lb). The Ton of Refrigeration (TR) is based on the 1 Ton mass of pure ice (2000 Pound or 907.184 kg) & not based on Tonne (2204.62 lb or 1000 kg) of ice. | ||||
- DERIVATION – IP UNIT:
Refrigeration effect 1 TR = 1 Ton (lb) x Latent heat of fusion/melting (BTU/lb) / Time duration of 24 (hr.)
1 TR = 2000 (lb) x 144 (BTU/lb)/ 24 (hr.)
1 TR = 12000 BTU/hr.
1 TR = 200 BTU/min (Based on the conversion, 1 hour = 60 minutes)
2. DERIVATION – SI UNIT:
Refrigeration effect 1 TR = 907.184 (kg) x Latent heat of fusion/melting (kJ/kg) / Time duration of 24 (hr.)
1 TR = 907.184 (kg) x 335 (kJ/kg) / 24 (hr.)
1 TR = 12662.78 kJ/hr.
1 TR = 211 kJ/min (Based on the conversion, 1 hour = 60 minutes)
1 TR = 3.517 kJ/s (Based on the conversion 1 minute = 60 Seconds)
1 TR = 3.517 kW (Based on the conversion, J/s =W)
REFERENCES:
- Textbook: Thermodynamics, Yunus A. Cengel and Michale A. Boles, Chapter – Refrigeration Cycle.
- Steam Table.
ABBREVIATIONS:
| BTU | British Thermal Unit |
| IP | Imperial System of Units |
| SI | International System of Units |
| TR | Ton of Refrigeration |