Friday, November 14, 2008

Mass Heat of Vaporization in HYSYS only for Pure Component

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Since the released of this article "Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS", a few young engineers raised a question. The proposed method does not work for pure component i.e. pure propane. How shall i obtain the latent heat of pure component using HYSYS ?

The proposed method in "Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS" is typically use to handle system with multi-component with large ranging of boiling point. It is typical useful for crude, naphtha, gasoline, condensate, etc. However, the propose method can not be used for pure component as it has only single boiling point at one pressure i.e. 152.4 Btu/lb at 100 psia for pure propane.



To obtain the latent heat of vaporization for pure component from HYSYS, it is pretty simple. From stream properties tab, latent heat of vaporization (Hvap) will be the Vapor Mass Enthalpy (Hv) minus Liquid Mass Enthalpy (Hl). Refer to above image. Hv = - 1032.6 Btu/lb, Hl = -1185 Btu/lb, thus Hvap = -1032.6 - (-1185) = 152.4 Btu/lb at 100 psia.



Another way is to read the Latent heat of Vaporization (Hvap) directly from properties tab. See above image. Mass Heat of Vap (Btu/lb) = 152.4 Btu/lb.

Important Note :
For pure component, latent heat of vaporization can be obtained by Vapor Mass Enthalpy (Hv) minus Liquid Mass Enthalpy (Hl).

For multi-component, latent heat of vaporization is NOT advisable to obtain by Vapor Mass Enthalpy (Hv) minus Liquid Mass Enthalpy (Hl). Rigorous method proposed in "Determine Latent Heat for Multi-Component and Relieving Area Using Rigorous Method in HYSYS" can be used.

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