NCEES Prob havc 514-515

[dlivy]

For 514:

According to the answer,

why h(in) is saturated liquid at discharge pressure@260psig? after expansion valve, I thought should be a lower pressure value.

For 515:

according the explanation from answer, why using 50psia and 60 psia @40 degree?

thanks a lot.

waiting.

 

[BORICUAZO]

For question 514: Preassure must be reduced in the expansion valve. Due to insuficient information for this problem, there is no other option than select h (in) as hf@260 psig. So, I assume that the expansion valve has no effect on the preassure, maybe is a damage one.

For question 515: I have no idea how they get that specific volume of .98 ft^3 / lbm. I just accept to use vg@20°F = .93343 ft^3 / lbm, for a final value of 106 cfm.

 

[dlivy]

thanks, IndependencePR

now, I understand 514 better.

generally, A,B,C,D 4 points. According to D point, 260psig;

Pa=Pd, so for A point, saturated liquid, we know h value of A point,

For B point, h value of B point = A point, that's why they use 260psig saturated liquid h value 45.7.

Best wishes to all the examinees!!!!