Refrigerant-134a enters the expansion valve of a refrigeration system at 160 psia as a saturated liquid and leaves at 30 psia. Determine the temperature and internal energy change across the valve.

Temperature : 92.9 F

Internal Energy change: - 2.53 Btu/lbm

Explanation:

As

mh1=mh2

h1=h2

In table A-11 through 13E

p2=120Psi, h1 = 41.79 Btu/lbm,

u1=41.49

So T1=90.49 F

P2=20Psi

h2=h1 = 41.79 Btu/lbm

T2 = - 2.43F

u2 = 38.96 Btu/lbm

T2-T1 = 92.9 F

u2-u1 = - 2.53 Btu/lbm