Rankine scale

2025-11-03T23:29:11Z

2607:F140:8801:0:0:0:1:141: Fix conversion error

{{Short description|Absolute temperature scale using Fahrenheit degrees}}
{{About|the temperature scale|the idealized thermodynamic cycle for a steam engine|Rankine cycle|the scale measuring recovery after stroke|Modified Rankin Scale}}
{{Infobox unit
| name = Rankine
| quantity = [[Temperature]]
| symbol = °R
| symbol2 = °Ra
| namedafter = [[W. J. M. Rankine]]
| convertfromx = yes
| calcinput = 491.67
| units1 = [[Kelvin scale]]
| inunits1 = {{convert|491.67|R|K|disp=out}}
| units2 = [[Celsius scale]]
| inunits2 = {{convert|491.67|R|C|disp=out}}
| units3 = [[Fahrenheit]]
| inunits3 = {{convert|491.67|R|F|disp=out}}
}}

[[File:William_Rankine_1870s.jpg | thumb | right | alt=A man with a beard and curly hair sitting at a table with an open book. | W.J. Rankine]]
The '''Rankine scale''' ({{IPAc-en|ˈ|r|æ|ŋ|k|ɪ|n}} {{respell|RANG|kin}}) is an [[absolute scale]] of [[thermodynamic temperature]] named after the [[University of Glasgow]] [[engineer]] and [[physicist]] [[W. J. M. Rankine]], who proposed it in 1859.<ref name="Merriam-Webster"/> Similar to the [[Kelvin|Kelvin scale]], which was first proposed in 1848,<ref name="Merriam-Webster">{{Cite Merriam-Webster|Rankine|access-date=2019-11-07}}</ref> zero on the Rankine scale is [[absolute zero]], but a temperature difference of one Rankine degree (°R or °Ra) is defined as equal to one [[Fahrenheit]] degree, rather than the [[Celsius]] degree used on the Kelvin scale. In converting from kelvin to degrees Rankine, {{convert|5//9|K|R|sigfig=1|order=flip|disp=x|{{nbsp}}{{=}}{{nbsp}}}} or {{convert|1|K|R|sigfig=2|disp=x|{{nbsp}}{{=}}{{nbsp}}}}. A temperature of {{convert|0|K|C F}} is equal to {{val|0|u=°R}}.<ref name="SP811">{{Cite journal |url=https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication811e2008.pdf |title=Guide for the use of the International System of Units (SI) |last1=Thompson |first1=Ambler |last2=Taylor |first2=Barry N. |date=2008 |language=en |doi=10.6028/nist.sp.811e2008 |access-date=2019-11-07 |journal=NIST Special Publication |volume=811 |pages=45-69}}</ref><ref>{{cite web |title=NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically |url=https://www.nist.gov/physical-measurement-laboratory/nist-guide-si-appendix-b8 |website=NIST.gov |publisher=National Institute of Standards and Technology |access-date=2 November 2025 |language=en |date=18 August 2025 |orig-date=1 February 2016}}</ref>

== Usage ==
The Rankine scale is used in engineering systems where heat computations are done using degrees Fahrenheit.<ref name="arstechnica">{{cite web |url=https://arstechnica.com/science/2022/08/warning-sign-nasa-never-finished-a-fueling-test-before-todays-sls-launch-attempt/ |title=Warning sign? NASA never finished a fueling test before today's SLS launch attempt |work=Ars Technica |first=Eric |last=Berger |date=2022-08-29 }}</ref>{{better citation needed|date=November 2025}}

The symbol for '''degrees Rankine''' is °R<ref name="SP811" /> (or °Ra if necessary to distinguish it from the [[Rømer scale|Rømer]] and [[Réaumur scale|Réaumur]] scales). By analogy with the SI unit [[kelvin]], some authors term the unit ''Rankine'', omitting the degree symbol.<ref name="dummies">{{Cite book |title=Thermodynamics For Dummies |last=Pauken |first=Michael |publisher=Wiley Publishing Inc. |page=20 |year=2011 |isbn=978-1-118-00291-9 |location=Indianapolis }}</ref><ref name="engineering">{{cite book |last=Balmer |first=Robert |year=2011 |title=Modern Engineering Thermodynamics |location=Oxford |publisher=Elsevier Inc. |page=10 |isbn=978-0-12-374996-3 }}</ref>

Some temperatures relating the Rankine scale to other temperature scales are shown in the table below.
{|class="wikitable" style="text-align:right"
! colspan="2" rowspan="2" |
! colspan="5" |Scale
|-
! scope="col" | Kelvin
! scope="col" | Rankine
! scope="col" | Fahrenheit
! scope="col" | Celsius
! scope="col" | Réaumur
|-
! rowspan="4" |Temperature
! scope="row" | [[Absolute zero]]
| {{convert|0|K|R F C|disp=table|abbr=on}}
| {{val|−218.52|u=°Ré}}
|-
! scope="row" | Freezing point of [[brine]]{{efn|The freezing point of [[brine]] is the zero point of Fahrenheit scale, old definition.<ref>{{Cite conference |last=Grigull |first=Ulrich |year=1986 |url=http://www.aihtc.org/pdfs/IHTC-8-Grigull.pdf |title=Heat Transfer |language=en |access-date=2022-08-29 }}</ref>}}
| {{convert|255.37|K|R F C|disp=table|abbr=on}}
| {{val|−14.22|u=°Ré}}
|-
! scope="row" | Freezing point of water{{efn|The ice point of purified water has been measured to be {{val|0.000089|end={{overline|10}}|u=degrees Celsius|fmt=none}}.<ref>{{Cite journal |last=Magnum |first=B.W. |date=June 1995 |title=Reproducibility of the Temperature of the Ice Point in Routine Measurements |url=http://www.cstl.nist.gov/div836/836.05/papers/magnum95icept.pdf |url-status=dead |journal=NIST Technical Note |volume=1411 |archive-url=https://web.archive.org/web/20070307055524/http://www.cstl.nist.gov/div836/836.05/papers/magnum95icept.pdf |archive-date=2007-03-07 |access-date=2007-02-11 }}</ref>}}
| {{convert|273.15|K|R F C|disp=table|abbr=on}}
| {{val|0|u=°Ré}}
|-
! scope="row" | [[Boiling point]] of water{{efn|For [[Vienna Standard Mean Ocean Water]] at one [[Atmosphere (unit)|standard atmosphere]] ({{val|101.325|u=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 precisely {{val|100|u=degC}}. However, the current definition results in a boiling point that is actually {{val|16.1|u=mK}} less. For more about the actual boiling point of water, see [[Vienna Standard Mean Ocean Water#VSMOW in temperature measurement|VSMOW in temperature measurement]].{{cn|date=November 2025}}}}
| {{convert|373.1339|K|R F C|disp=table|abbr=on|sigfig=6}}
| {{val|79.9871|u=°Ré}}
|}

== See also ==
* [[Outline of metrology and measurement]]
* [[Comparison of temperature scales]]

== Notes ==
{{notelist}}

== References ==
{{reflist}}

== External links ==

{{Scales of temperature}}
{{Portal bar|Energy}}

[[Category:Scales of temperature]]
[[Category:1859 introductions]]

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Rankine scale