Give the phase and the missing property of P, T, v and x. a. R-134a T = -10 F, P

Question

Give the phase and the missing property of P, T, v and x.
a. R-134a T = -10 F, P = 18 psia
b. R-134a P = 50 psia, v = 1.3 ft3/lbm
c. NH3 T = 120 F, v = 0.9 ft3/lbm
d. NH3 T = 200 F, v = 11 ft3/lbm

Explanation / Answer

a. P > Psat = 16.76 psia This state is compressed liquid so x is undefined and v = vf = 0.01173 ft3/lbm b. v > vg = 0.95 ft3/lbm so superheated vapor Look then in Table F.10.2 under 50 psia which is not printed so we must interpolate between the 40 and 60 psia sections. (60 psia, 1.3 ft3/lbm) : T = 300 F (40 psia, 1.3 ft3/lbm) : T = 66.6 F Linear interpolation between these gives T = 183 F for a better accuracy we must use the computer software. c. Look in Table F.8.1 at 120 F: v vg = 0.3388 ft3/lbm so sup. vapor Look in Table F.8.2 start anywhere say at 15 psia, 200 F there we see v = 27.6 ft3/lbm so P larger We can bracket the state between 35 and 40 psia so we get P = 35 + 5 11 – 11.7410.2562 – 11.74 = 37.494 psia

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