British Thermal Units to Liter-atmospheres (BTU to L⋅atm)

1 British thermal unit equals 10.41259169 liter-atmospheres (rounded).

1 British thermal unit = 10.41259169 liter-atmospheres

How to convert British thermal units to liter-atmospheres

To convert British thermal units to liter-atmospheres, multiply the number of British thermal units by 10.41259169. The factor is rounded to 10 significant digits. To go the other way, multiply liter-atmospheres by 0.09603756972 (rounded).

liter-atmospheres = British thermal units × 10.41259169

Example: 10 British thermal units = 104.1259169 liter-atmospheres.

The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.

About these units

British Thermal Unit (BTU)

US & ImperialCurrent unit

The International Table BTU, exactly 1,055.05585262 joules. The energy to heat one pound of water by one degree Fahrenheit; used for heating, cooling and gas appliances in the US.

Few energy units come in as many versions as the British thermal unit. It was defined as the heat needed to raise one pound of liquid water by one degree Fahrenheit, but because water's heat capacity shifts slightly with temperature, definitions differ by up to 0.5 percent: about 1,054.35 J for the thermochemical Btu, 1,054.80 J at 59 degrees Fahrenheit (used for American natural gas pricing), 1,054.68 J at 60 degrees (mainly Canadian), and 1,059.67 J at 39 degrees. A 1942 note suggests the term apparently arose in the United States and was later adopted in Britain.

The version on this site is the International Table Btu, about 1,055.06 J, which comes from the international steam table conferences that tied heat units to the joule. Joule's own 1850 experiments gave 772.692 foot-pounds of work per Btu, the number that first linked heat to mechanical effort.

Today the Btu survives in natural gas pricing (MMBtu means a million Btu), US building energy reporting, and equipment ratings in Btu per hour. One ton of air-conditioning is 12,000 Btu/h, or 3.52 kW. A single wooden kitchen match burning releases about one Btu.

1 British thermal unit = 1,055.055853 joules (approximately).

Sources: Wikipedia: British thermal unit; Wikipedia: James Prescott Joule

Liter-atmosphere (L⋅atm)

ScientificTraditional unit (still used in some regions)

Exactly 101.325 joules, the work of expanding a gas by one liter against one standard atmosphere.

Pressure times volume has the dimensions of energy, which is why gas chemists found it convenient to multiply a pressure in atmospheres by a volume in litres. One litre-atmosphere is 1 atm acting over 1 L, and the figure used here is 101.325 J. The arithmetic is simple: the standard atmosphere is 101,325 Pa, and a litre is 0.001 cubic metre, so the product is 101.325 pascal-cubic-metres, which is joules.

The atmosphere in this definition goes back to the barometer, being first set by a 760 mm column of mercury at 0 degrees Celsius. The tenth General Conference on Weights and Measures in 1954 fixed it as exactly 1,013,250 dynes per square centimetre, with no dependence on any substance. In 1982 IUPAC moved its reference pressure for substance data to 100 kPa. Expressed in thermochemical calories, one litre-atmosphere is about 24.2 cal.

1 liter-atmosphere = 101.325 joules (exactly).

Sources: Wikipedia: Conversion of units of energy; Wikipedia: Atmosphere (unit); Wikipedia: Calorie

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