Other Definitions
british thermal unit (dict)
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British Thermal UnitThe British thermal unit (BTU) is a non-metric unit of energy, used in the United States and, to a lesser extent, the UK (although the BTU is extremly rare in the UK now). The SI unit is the joule (J), which is used by most other countries. A BTU is defined as the amount of heat required to raise the temperature of one pound avoirdupois of water by one degree Fahrenheit; specifying the temperature range over which this happens leads to a number of slightly different BTU values, varying over a range of about 0.5%: | width="100"| Name !!width="140"| Value (J) !! Notes | | 39F | ≈ 1059.67 | Uses the calorie value of water at its maximum density (39.1–39.2F) | | Mean | ≈ 1055.87 | Uses a calorie averaged over the 32F to 212F range | | IT | ≡ 1055.05585262 | The most widespread BTU, uses the International Steam Table (IT) calorie, itself defined for water at 14.5C (58.1F) by the Fifth International Conference on the Properties of Steam, held in London in July 1956. | | 59F | ≡ 1054.804 | Chiefly American. Uses the 15C calorie, itself defined as exactly 4185.5 J (Comit international 1950; PV, 1950, 22, 79-80) | | 60F | ≈ 1054.68 | Chiefly Canadian | | 63F | ≈ 1054.6 | Possibly apocryphal | | ISO | ≡ 1054.5 | ISO 31 Quantities and units (?) | | Thermochemical | ≡ 1054.35026444 | (Calculated from 9489.152 380 4 9) Uses the thermochemical calorie of exactly 4184 J | The BTU is often used to describe the heat value of fuels, or the heating and cooling capacity of a system (such as a barbecue grill). One BTU is approximately: The BTU/hour (BTU per hour) is the unit of power most commonly associated with the BTU. - 1 horsepower is approximately 2500 BTU/hour
- 1 watt is approximately 3.4 BTU/hour
- 1000 BTU/hour is approximately 290 W
A unit called the quad (short for quadrillion) is defined as 1015 BTUs, which is about 1.055×1018 joules, and the therm is defined in the United States and European Union as 100,000 BTU – but the U.S. uses the BTU59F whilst the E.C. uses the BTUIT. The BTU should not be confused with the Board of Trade Unit (B.O.T.U.), which is a much larger quantity of energy. See also
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