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Rankine scale

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Absolute temperature scale using Fahrenheit degrees

This article is about the temperature scale. For the idealized thermodynamic cycle for a steam engine, seeRankine cycle. For the scale measuring recovery after stroke, seeModified Rankin Scale.

Rankine
Unit of	Temperature
Symbol	°R, °Ra
Named after	W. J. M. Rankine
Conversions
491.67 °Rin ...	... corresponds to ...

Kelvin	273.15 K
Celsius	0.00 °C
Fahrenheit	32.00 °F

A man with a beard and curly hair sitting at a table with an open book. — W.J. Rankine

TheRankine scale (/ˈræŋkɪn/RANG-kin) is anabsolute scale ofthermodynamic temperature named after theUniversity of Glasgow engineer andphysicist W. J. M. Rankine, who proposed it in 1859.^[1] Similar to theKelvin scale, which was first proposed in 1848,^[1] zero on the Rankine scale isabsolute zero, but a temperature difference of one Rankine degree (°R or °Ra) is defined as equal to oneFahrenheit degree, rather than theCelsius degree used on the Kelvin scale. In converting from kelvin to degrees Rankine, 1 °R = 5/9 K or 1 K = 1.8 °R. A temperature of 0 K (−273.15 °C; −459.67 °F) is equal to0 °R.^[2]^[3]

Usage

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The Rankine scale is used in engineering systems where heat computations are done using degrees Fahrenheit.^[4]^{[better source needed]}

The symbol fordegrees Rankine is °R^[2] (or °Ra if necessary to distinguish it from theRømer andRéaumur scales). By analogy with the SI unitkelvin, some authors term the unitRankine, omitting the degree symbol.^[5]^[6]

Some temperatures relating the Rankine scale to other temperature scales are shown in the table below.

		Scale
		Kelvin	Rankine	Fahrenheit	Celsius	Réaumur
Temperature	Absolute zero	0 K	0.00 °R	−459.67 °F	−273.15 °C	−218.52 °Ré
	Freezing point ofbrine^[a]	255.37 K	459.67 °R	0.00 °F	−17.78 °C	−14.22 °Ré
	Freezing point of water^[b]	273.15 K	491.67 °R	32.00 °F	0.00 °C	0 °Ré
	Boiling point of water^[c]	373.1339 K	671.641 °R	211.971 °F	99.9839 °C	79.9871 °Ré

Notes

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^The freezing point ofbrine is the zero point of Fahrenheit scale, old definition.^[7]
^The ice point of purified water has been measured to be0.00008910 degrees Celsius.^[8]
^ForVienna Standard Mean Ocean Water at onestandard atmosphere (101.325 kPa) when calibrated solely per the two-point definition of thermodynamic temperature. Older definitions of the Celsius scale once defined the boiling point of water under one standard atmosphere as being precisely100 °C. However, the current definition results in a boiling point that is actually16.1 mK less. For more about the actual boiling point of water, seeVSMOW in temperature measurement.^{[citation needed]}