Complete the blank cells in the following table of properties of steam. In
the last column describe the condition of steam as compressed liquid,
saturated mixture, superheated vapor, or insufficient information; and, if
applicable, give the quality.
T(oC) P (kPa) V (m3/kg) U (kJ/kg) Quality
x Phase Description
a.) 30 200
b.) 130 270.28
c.) 400 1.5493
d.) 300 0.500
e.) 500 3084
3 comments:
Sorry the formatting gets messed up in the blog.
Notice that I changed P to 270.28 kPa in part (b). This is the saturation pressure on NIST. This way, the problem is the same as it was in HW #2.
I'm having issues with part e. In the previous homework and this homework I am finding T @ 300 kPa and 3084 kJ/kg to be 309.85 degC and a specific volume of 0.53202 m^3/kg...I pulled both of these values directly from NIST. On HW 1, I interpolated between T's of 300 and 400degC and their respected values of H~ to find V~. I found the T and U values in the superheated vapor tables in the binder. I get the same answer using both sources and I'm still getting the wrong solution. Am I missing something in this problem (twice)???
jolene 8:59 PM
Something is wrong with what you did and I am not sure what ! Here is how I did the problem.
Start with P=300 kPa and determine Usatvap. You find that Usatvap < 3084 and you conclude this is a superheated vapor, right ? So, in NIST, you want to go back and do isobaric properties at 500 kPa. I used T = {300,700}, by 20degC steps. I scanned the U column until I found a pair of T's that bracket the value of 3084. Then, I interpolated. If you feel lazy, you can just keep zooming in on smaller ranges using NIST to get the correct T and other properties. But you won't have NIST on the test next Tue !
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