British thermal unit (redirected from Thermal unit)

British thermal unit

n. Abbr. Btu

1. The quantity of heat required to raise the temperature of one pound of water from 60° to 61°F at a constant pressure of one atmosphere.

2. The quantity of heat equal to ¹/₁₈₀ of the heat required to raise the temperature of one pound of water from 32° to 212°F at a constant pressure of one atmosphere.

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British thermal unit

BTU, a unit of heat being the amount necessary to raise the temperature of 1 pound of water from 39 to 40°F, generally considered the equivalent of 252 calories.