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Differential equation for vapour pressure as a function of temperature.

[ In Korean. / En coréen.]

Author(s) : PARK K. K.

Summary

A new approach to develop a vapour pressure equation is proposed. Nondimensional slope term in the Clapeyron equation and logarithm of reduced pressure multiplied by a coefficient are added together to set up a differential equation (DE). The coefficient is a function of temperature and is determined such that the homogeneous solution of the DE is a term in the Wagner-type vapour pressure equation. Next, behaviour of a source function of the DE is observed using saturation data from NIST Chemistry Webbook for H2O, CO2 and CH4. The observation suggests that the source function is essentially linear to reduce temperature, which completes the DE. Solving the DE gives a new 3-parameter vapour pressure equation. Vapour pressure data from the Webbook for 45 pure substance refrigerants are fitted to the new equation yielding an average AAD of 0.12%. The results compares with existing 3-parameter vapour pressure correlations, such as Riedel (0.44%), Mejbri-Bellagi (0.23%) and Xiang-Tan (0.21%). The equation proposed in this work is valid over the entire temperature range where data points exist.

Details

  • Original title: [ In Korean. / En coréen.]
  • Record ID : 2009-0999
  • Languages: Korean
  • Source: The 3rd Korean Congress of Refrigeration.
  • Publication date: 2009/03/19

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