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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 .
This definition ultimately became the statement that 1 IT calorie is exactly 4.1868 J. [4] [8] The Btu is then calculated from the calorie as is done for the thermochemical definitions of the BTU and the calorie, as in International standard ISO 31-4 Quantities and units—Part 4: Heat and British Standard BS 350:Part 1:1974 Conversion factors ...
The calorie is defined as the amount of thermal energy necessary to raise the temperature of one gram of water by 1 Celsius degree, from a temperature of 14.5 °C, at a pressure of 1 atm. For thermochemistry a calorie of 4.184 J is used, but other calories have also been defined, such as the International Steam Table calorie of 4.1868 J.
In this example the total insulance is 1.64 K⋅m 2 /W. The thermal transmittance of the structure is the reciprocal of the total thermal insulance. The thermal transmittance of this structure is therefore 0.61 W/(m 2 ⋅K).
The heat capacity of an object is an amount of energy divided by a temperature change, which has the dimension L 2 ⋅M⋅T −2 ⋅Θ −1. Therefore, the SI unit J/K is equivalent to kilogram meter squared per second squared per kelvin (kg⋅m 2 ⋅s −2 ⋅K −1 ).
≡ 1 ft/(h⋅s) = 8.4 6 × 10 −5 m/s 2: foot per minute per second: fpm/s ≡ 1 ft/(min⋅s) = 5.08 × 10 −3 m/s 2: foot per second squared: fps 2: ≡ 1 ft/s 2 = 3.048 × 10 −1 m/s 2: gal; galileo: Gal ≡ 1 cm/s 2 = 10 −2 m/s 2: inch per minute per second: ipm/s ≡ 1 in/(min⋅s) = 4.2 3 × 10 −4 m/s 2: inch per second squared ...
The heat transfer coefficient has SI units in watts per square meter per kelvin (W/(m 2 K)). The overall heat transfer rate for combined modes is usually expressed in terms of an overall conductance or heat transfer coefficient, U. In that case, the heat transfer rate is: ˙ = where (in SI units):
6 × 10 1: tech: the power consumption of a typical household incandescent light bulb: 10 2: hecto-(hW) 1 × 10 2: biomed: approximate basal metabolic rate of an adult human body [16] 1.2 × 10 2: tech: electric power output of 1 m 2 solar panel in full sunlight (approx. 12% efficiency), at sea level 1.3 × 10 2: tech: peak power consumption of ...