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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.
U = Overall heat transfer coefficient in Btu/(ft2-hr-deg F) A = Area in square feet T1 = outdoor temperature in degrees F T2 = indoor temperature in degrees F For heat gains due to people, equipment (hooded and unhooded), and lighting
[1] [2] It therefore has units of BTU/watt-hr. The higher the HSPF rating of a unit, the more energy efficient it is. An electrical resistance heater, which is not considered efficient, has an HSPF of 3.41. [3] Depending on the system, an HSPF ≥ 9 can be considered high efficiency and worthy of a US Energy Tax Credit. [4]
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]
For example, consider a 5000 BTU/h (1465-watt cooling capacity) air-conditioning unit, with a SEER of 10 BTU/(W·h), operating for a total of 1000 hours during an annual cooling season (e.g., 8 hours per day for 125 days). The annual total cooling output would be: 5000 BTU/h × 8 h/day × 125 days/year = 5,000,000 BTU/year
This thermal energy input of 1 kWh = 3.6 MJ = 3,412 Btu Therefore, the heat rate of a 100% efficient plant is simply 1, or 1 kWh/kWh, or 3.6 MJ/kWh, or 3,412 Btu/kWh To express the efficiency of a generator or power plant as a percentage, invert the value if dimensionless notation or same unit are used.
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12,000.00 Btu IT /h 2,593.90 ft⋅lbf/s A ton of refrigeration ( TR or TOR ), also called a refrigeration ton ( RT ), is a unit of power used in some countries (especially in North America) to describe the heat-extraction capacity of refrigeration and air conditioning equipment.