Water vapor and mechanical work

A comparison of Carnot and steam cycles

Research output: Contribution to journalArticle

Abstract

The impact of water vapor on the production of kinetic energy in the atmosphere is discussed here by comparing two idealized heat engines: the Carnot cycle and the steam cycle. A steam cycle transports water from a warm moist source to a colder dryer sink. It acts as a heat engine in which the energy source is the latent heat of evaporation. It is shown here that the amount of work produced by a steam cycle depends on relative humidity and is always less than that produced by the corresponding Carnot cycle. The Carnot and steam cycles can be combined into a mixed cycle that is forced by both sensible and latent heating at the warm source. The work performed depends on four parameters: the total energy transport; the temperature difference between the energy source and sink; the Bowen ratio, which measures the partitioning between the sensible and latent heat transports; and the relative humidity of the atmosphere. The role of relative humidity on the work produced by a steam cycle is discussed in terms of the Gibbs free energy and in terms of the internal entropy production.

Original languageEnglish (US)
Pages (from-to)91-102
Number of pages12
JournalJournal of the Atmospheric Sciences
Volume68
Issue number1
DOIs
StatePublished - Jan 2011

Fingerprint

relative humidity
water vapor
engine
cycle transport
Bowen ratio
Gibbs free energy
atmosphere
kinetic energy
entropy
partitioning
evaporation
heating
energy
comparison
temperature
water
energy source
cold
parameter

Keywords

  • Energy transport
  • Hydrologic cycle
  • Kinetic energy
  • Latent heating/cooling
  • Thermodynamics
  • Water vapor

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Water vapor and mechanical work : A comparison of Carnot and steam cycles. / Pauluis, Olivier.

In: Journal of the Atmospheric Sciences, Vol. 68, No. 1, 01.2011, p. 91-102.

Research output: Contribution to journalArticle

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