BTU/lb
BTU per pound
Specific latent heatexact by definition
The BTU per pound is the customary US unit of latent heat, exactly 2326 J/kg using the International Table BTU. The factor follows exactly from the IT BTU of 1055.05585262 J divided by the pound of 0.45359237 kg, so it is exact by definition. Water's latent heat of fusion is about 144 BTU/lb and of vaporisation about 970 BTU/lb at atmospheric pressure.
| 1 BTU/lb | 2,326 J/kg |
Where the unit came from
The 144 BTU/lb figure is the origin of the refrigeration ton: melting one short ton of ice in 24 hours absorbs 2000 × 144 = 288 000 BTU, which is 12 000 BTU/h, the definition of one ton of cooling.
Solvers that use specific latent heat