Complete the following table for water (revisited from HW2) using either the NIST Webbook or the Thermal Fluids Excel Plug in. Be sure to cite which one that you used. Your grade will be based mostly on the use of technology, not on the answers. Your solution must be different than your solution from HW2.
T(oC) P(kPa) H(kJ/kg) x(kg vap/kg) Phase Description
a.) P = 200 kPa and x = 0.7 kg vap/kg
b.) T = 140 degC and H = 1800 kJ/kg
c.) P = 950 kPa and x = 0 kg vap/kg
d.) T = 80 degC and P = 500 kPa
e.) P = 800 kPa and H = 3161.7 kJ/kg
No Old Comments.
5 comments:
In part C of this problem, if all we know is the pressure and x=0, can we assume that we are saturated liquid? This is what I did for HW2, and just took the numbers directly from the tables.
Anonymous:
Yes. When x = 0 kg vap/kg the system contains a saturated liquid.
continuing along that line, so what do we do if it is a subcooled liquid, or superheated vapor? do we write x as N/A? would a problem ever give x as 0, or 1, but want to be classified as a subcooled or superheated, instead of saturated? thanks.
Hi Anonymous,
You are exactly right. Quality, x, is not defined for subcooled liquids or superheated vapors. So, N/A would be the right answer for x in those cases.
No, if x has a value (always between 0 and 1) then the system cannot contain subcooled liquid or superheated vapor at an equilibrium state.
Sometimes, if you make an incorrect assumption that a system contains a two phase mixture, you may calculate a value of x < 0 or x > 1. You should think of this as an indication that the system does not contain a two-phase mixture. If you calculate x < 0 then the system probably contains a subcooled liquid. If you calculate x >1, then the system probably contains a superheated vapor. This is unusual and can be avoided by carefully comparing actual properties to saturation properties, but it may be helpful to be aware of this little quirk.
Best of luck !
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