Chapter2, Lesson D - Isothermal Vaporization of Water

2D-1 :	Isothermal Vaporization of Water					4 pts

The temperature of 10 lb_m of water is held constant at 205^oF. The pressure is reduced from a very high value until vaporization is complete. Determine the final volume of the steam in ft³.

Read :	The initial state of the water is probably a subcooled liquid (or even a supercritical fluid), since the pressure is "very high". The final state of the water is a saturated vapor because the vaporization of the water is just barely complete. The temperature of the final saturated vapor is the same as the initial temperature: 205^oF. This is an isothermal process !





Given :	m	10	lb_m
	T	205	^oF

Find :	V_final	???	ft³

Solution :	We need to determine the volume of the system and we are given the mass of water in the system.


	We need to determine the specific volume of the system because :

						Eqn 1

	Because we know that the water in the final state is a sat'd vapor, we can look up its specific volume in the Saturated Temperature Table of the Steam Tables at 205^oF.



	The problem is that a temperature of 205^oF is not listed in the Saturation Temperature Table.

	So, we must interpolate to determine the value :			T_sat	V_{sat vap}
	So, we must interpolate to determine the value :			(^oF)	(ft³/lb_m)
				200	33.63
				205	???
				210	27.82

						Eqn 2

						Eqn 3

	slope	-0.581	(ft³/lb_m)/^oF	V_{sat vap}	30.725	ft³/lb_m
	Now that we now the value of the specific volume of the saturated vapor, and the system contains ALL saturated vapor (x = 1), we can plug values into Eqn 1 and answer the question.




	V_final	307	ft³

Example Problem with Complete Solution