![]() Anyone is free to disagree with the logical explanation.In this work, we present an altered partition function that leads to an improved calculation of the enthalpy and entropy of vaporization in the framework of quantum cluster equilibrium theory. Therefore, the energy required to convert water from saturated liquid to saturated vapor during the process of vaporization exceeds the energy returned by the condensation process when the saturated vapor converts to saturated water by about 6.5 kj/kg-k In the case of condensation since the entropy creation is negative, the net heat released as steam converts to saturated water = To summarize, while in both cases of vaporization and condensation, from saturated water to saturated vapor during vaporization and from saturated vapor to saturated water the enthalpy remains the same, in the case of vaporization positive entropy creation adds about 6.5 kj/kg-k more heat requirement for conversion of water to saturated steam. Primarily the decrease in entropy takes place due to the conversion of more disordered vapor to more ordered liquid water molecules. As we proceed from saturated vapor to saturated water outline on the dome on 100 degc/0.1 Mpa line entropy decreases by the same amount of 6.5 kj/kg-k what was the entropy creation in vaporization. When water vapor condenses to liquid water, the same latent heat is released however the entropy of the water is decreased, so something must have its entropy increased to compensate. Entropy generation in the vaporization is always positive, since the degree of disorder increases in the transition from a liquid in a relatively small volume to a vapor or gas occupying a much larger space. This is an output of huge expansion and disorder created by steam. The total entropy increase is about 6.5 kj/kg-k if we consider the intersection of isothermal/isobaric line corresponding to 100 degc, 0.1Mpa with saturated water and saturated vapor curves. It may be observed, as we move from the saturated water line on the dome towards the saturated vapor line on the right the entropy increases. This vapor generation is the source of entropy in the process of vaporization. ![]() As more and more water converts to vapor on this line the dryness fraction ‘q’ increases with simultaneous generation of more and more vapor. As we proceed to right the supply of energy breaks intermolecular bonds. This is the line where the two phases coexist in equilibrium. Let us follow the horizontal line corresponding to 100 degc and 0.1 Mpa which is 1 bar from left to right on the TS diagram. As we proceed to right on this isothermal and isobaric line from saturated water to saturated vapor contour of the dome, the vaporization simultaneously proceeds with dryness fraction ‘q ‘increasing from zero to 1. By the definition of entropy, the heat transferred to or from a system equals the area under the T-s curve of the process. On the right q =1 on the saturated vapor line meaning it is dry steam with no water. Inside the dome, both water and steam coexist as two phases. In a phase transition when both phases coexist in equilibrium, the difference in Gibbs free energy is equal to zero, ∆G=0. On the extreme left on the saturated water pink line, the dryness fraction = 0 which shows it is all water. q represents the dryness fraction of steam + water inside the two-phase dome where they coexist together. Above the critical point, there is the supercritical region. On the left of the dome, there is water and on the right of the dome, there is superheated steam. At the topmost point of the dome where saturated water line insects the saturated vapor line is the critical point. ![]() The pink outline of the dome on the left represents saturated water while the red outline of the come on the right side represents the saturated water vapor line. The x-axis is entropy and the y-axis is temperature. ![]() The diagram below is a temperature entropy diagram of water.
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