Gauge Pressure and Specific Volume of Saturated Steam
 
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Observe the relationship between gauge pressure and the specific volume of the saturated steam.The specific volume of steam decreases as the system pressure increases. At atmospheric pressure a pound of steam occupies about 1,600 times the volume of a pound of condensate. As pressure increases in the system, the specific volume of the steam decreases. Because of this principle, a greater quantity of steam is available in a smaller space (pipe, heat exchanger) at higher pressures. This is why steam is often distributed at higher pressure but is reduced to a lower pressure to perform specific heat-transfer functions. Rising pressure constrains the molecules from moving apart when water vaporizes. At the critical pressure of 3206.2 psia, the specific volumes of liquid and gas are equal.  |
