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What is Latent Heat of Condensation – Enthalpy of Condensation – Definition

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For condensation, latent heat effects associated with the phase change are significant, similarly as for boiling, but in reverse. Latent Heat of Condensation – Enthalpy of Condensation
dry-steam-saturated-vapor-minFor condensation, latent heat effects associated with the phase change are significant, similarly as for boiling, but in reverse. Note that the enthalpy of condensation (or heat of condensation) is by definition equal to the enthalpy of vaporization with the opposite sign. Latent heat is the amount of heat added to or removed from a substance to produce a change in phase. During vaporisation, this energy breaks down the intermolecular attractive forces, and also must provide the energy necessary to expand the gas (the pΔV work).  When latent heat is added or removed, no temperature change occurs. The enthalpy of vaporization is a function of the pressure at which that transformation takes place.
Latent heat of vaporization - water at 0.1 MPa, 3 MPa, 16 MPa
The heat of vaporization diminishes with increasing pressure, while the boiling point increases. It vanishes completely at a certain point called the critical point.

Latent heat of condensation – water at 0.1 MPa (atmospheric pressure)

hlg = – 2257 kJ/kg

Latent heat of condensation – water at 3 MPa

hlg = – 1795 kJ/kg

Latent heat of condensation – water at 16 MPa (pressure inside a pressurizer)

hlg = – 931 kJ/kg

The heat of condensation diminishes with increasing pressure, while the boiling point increases. It vanishes completely at a certain point called the critical point. Above the critical point, the liquid and vapor phases are indistinguishable, and the substance is called a supercritical fluid.

The heat of condensation is the heat released to completely condendse a unit of saturated vapor and it equal to – hlg =hl – hg.

The heat that is necessary to melt (or freeze) a unit mass at the substance at constant pressure is the heat of fusion and is equal to hsl = hl − hs, where hs is the enthalpy of saturated solid and hl is the enthalpy of saturated liquid.

Phase changes - enthalpy of vaporization
Latent heat of vaporization – water at 0.1 MPa. Dominant part of heat absorbed.
 
References:
Heat Transfer:
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  2. Heat and Mass Transfer. Yunus A. Cengel. McGraw-Hill Education, 2011. ISBN: 9780071077866.
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Nuclear and Reactor Physics:

  1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
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Advanced Reactor Physics:

  1. K. O. Ott, W. A. Bezella, Introductory Nuclear Reactor Statics, American Nuclear Society, Revised edition (1989), 1989, ISBN: 0-894-48033-2.
  2. K. O. Ott, R. J. Neuhold, Introductory Nuclear Reactor Dynamics, American Nuclear Society, 1985, ISBN: 0-894-48029-4.
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  4. E. E. Lewis, W. F. Miller, Computational Methods of Neutron Transport, American Nuclear Society, 1993, ISBN: 0-894-48452-4.

See also:

Boiling and Condensation

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