R134a enters a tubular heat exchanger at 100 F with a qualit

R-134a enters a tubular heat exchanger at 100 F with a quality of 75%. Heat is transferred out of the system in an aergonic process, until the fluid leaves as saturated liquid at 0F. Determine the heat transfer per lbm of R-134a flowing through the heat exchanger. Neglect any changes in kinetic and potential energies. Assume steady-state operation.

Solution

Given data

Working fluid is R-134a

It enters the heat exchanger at 100 F & x = 0.75

It exits as a saturated liquid at 0 F

At 100 F & x = 0.75

h₁ = 108.86 + 0.75 (71.79)

= 180.05 Btu/lbm

At 0 F

h₂ = 75.92 Btu/lbm

Heat tranfer per lbm = h₁ - h₂

= 180.05 - 75.92

= 104.13 Btu/lbm