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The therm (symbol, thm) is a non-SI unit of heat energy equal to 100,000 British thermal units (BTU), [1] and approximately 105 megajoules, 29.3 kilowatt-hours, 25,200 kilocalories and 25.2 thermies. One therm is the energy content of approximately 100 cubic feet (2.83 cubic metres) of natural gas at standard temperature and pressure .
The Btu should not be confused with the Board of Trade Unit (BTU), an obsolete UK synonym for kilowatt hour (1 kW⋅h or 3,412 Btu). The Btu is often used to express the conversion-efficiency of heat into electrical energy in power plants. Figures are quoted in terms of the quantity of heat in Btu required to generate 1 kW⋅h of electrical energy.
In the United States, U-value is expressed as British thermal units (Btu) per hour-square feet-degrees Fahrenheit: Btu/(h⋅ft 2 ⋅°F) Within this article, U-values are expressed in SI unless otherwise noted. To convert from SI to US customary values, divide by 5.678. [1]
British thermal unit: Btu Btu 1.0 Btu (1.1 kJ) BTU BTU million British thermal units: MMBtu MMBtu 1.0 MMBtu (1.1 GJ) e6BTU BTU British thermal unit (IT) Btu-IT Btu IT ...
This Wikipedia page provides a list of units of energy used in the template for converting measurements.
BTU IT /h ≡ 1 BTU IT /h ≈ 0.293 071 W: BTU (International Table) per minute: BTU IT /min ≡ 1 BTU IT /min ≈ 17.584 264 W: BTU (International Table) per second: BTU IT /s ≡ 1 BTU IT /s = 1.055 055 852 62 × 10 3 W: calorie (International Table) per second: cal IT /s ≡ 1 cal IT /s = 4.1868 W: erg per second: erg/s ≡ 1 erg/s = 10 −7 ...
The cited Andersland Charts include corresponding water content percentages for easy measurements. The TPRC Data Book has been quoting de Vries with values of 0.0251 and 0.0109 W⋅cm −3 ⋅Kelvin −1 for the thermal conductivities of organic and dry mineral soils respectively but the original article is free at the website of their cited ...
So, for a boiler that produces 210 kW (or 700,000 BTU/h) output for each 300 kW (or 1,000,000 BTU/h) heat-equivalent input, its thermal efficiency is 210/300 = 0.70, or 70%. This means that 30% of the energy is lost to the environment. An electric resistance heater has a thermal efficiency close to 100%. [8]