Solving Steam Problems: Calculating Heat Transfer with Thermodynamic Properties

[FrankPais]

1.I am currently working through some steam questions and I am struggling with this problem. I am using "Thermodynamic and Transport Properties of Fluids byG.F.C Rogers and Y.R Mayhew

Here are my questions as it is written:

"(A) Steam at 30 bar, 375 degrees C flows through a cooling coil with a negligible change in velocity and pressure, such that the exit dryness fraction is 0.5.

Calculate the heat transfer per kg of water substance."

I have worked this out by using the steady flow equation, linear interpolation and the unknown which was the "h2" value using h=(1-x)hf+xhg. (Obviously not in that order)

Here is my issue below...

One kg of steam at 30 bar, 375 degrees C, is contained in a rigid container and is cooled until the pressure is 13 bar.

Calculate the final dryness fraction and the heat transfer

Now I have been given a data sheet with the equation for x (dryness fraction) which is x= mass of saturated steam/total mass but I am still unsure how to calculate the dryness fraction from the information from the Steam Tables as I can not get the value of -966kJ

So I am asking for your help with this please.

I also have many more problems as well I need help with.

Many thanks

Scott

2. x (dryness fraction) which is x= mass of saturated steam/total mass

I believe once I have calculated the dryness fraction I need to use the steady flow equation of Q=m(h2-h1) to calculate the work done [I have disregarded the other values as they state that they are negligible]



3. I can not continue this until I know how to work out the dryness fraction correctly. As I have obviously not worked out the dryness fraction correctly I can not seem to get the correct answer.

PLEASE HELP

 

[AvroArrow]

ME WITH THIS. To calculate the dryness fraction you will need to use the Steam Table values for enthalpy, specific volume, and entropy at both the inlet and exit states of your process. You can then use the steam table to derive the dryness fraction from the formula x= mass of saturated steam/total mass. Once you have the dryness fraction, you can use the steady flow equation of Q=m(h2-h1) to calculate the work done [I have disregarded the other values as they state that they are negligible]. Hope this helps!