Why is specific volume of saturated water greater at 1 MPA than at 0.1 MPA during the phase change process?

check out the T-V diagram here in the link. http://www.ohio.edu/mechanical/thermo/Intro/Chapt.1_6/Chapter2a.html

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    $\begingroup$ Saturated water? Can you explain what this means and ideally give a link to an article that describes the specific volumes you mention? $\endgroup$ – John Rennie Sep 14 '14 at 9:41
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    $\begingroup$ By Saturated water I mean water that is about to vaporize. $\endgroup$ – thermonerd Sep 14 '14 at 9:45
  • $\begingroup$ Do you mean, why the specific volume is bigger at higher pressure before it starts vaporizing? Are you at the Saturated Liquid line? $\endgroup$ – Steeven Sep 14 '14 at 10:03
  • $\begingroup$ Yes Steeven exactly. $\endgroup$ – thermonerd Sep 14 '14 at 10:07
  • $\begingroup$ Yeah I'm at the line connecting the saturated liquid to the saturated vapour,i wanted to know why the line gets shorter as the pressure increases $\endgroup$ – thermonerd Sep 14 '14 at 10:15

For saturated water, you must have vapor and liquid water together, presumably at thermal equilibrium. In addition, the pressure of the saturated water must be the vapor pressure at the specified temperature. The Antoine equation specifies vapor pressure as a function of temperature, and it also says that a higher vapor pressure corresponds to a higher temperature. At higher temperatures (hence, at higher pressures), the density of liquid water is lower, so the specific volume is higher.

For further info, see http://antoine.frostburg.edu/chem/senese/101/liquids/faq/antoine-vapor-pressure.shtml


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