Your new job at a domestic refrigerator manufacturing company involves the design of expansion valves. The liquid refrigerant passes through the expansion valve (also called a throttle valve), where its pressure abruptly decreases, causing flash evaporation of 35% of the liquid.

The resulting mixture of liquid and vapor, at a lower temperature and pressure, then travels through the refrigerator's evaporator coil and is completely vaporized by cooling the warm air of the space being refrigerated. The resulting refrigerant vapor returns to the refrigerator's compressor inlet to complete the thermodynamic cycle.

For a new refrigerator design, saturated liquid Refrigerant 134a enters the expansion valve at 80.0°F and exits at 10.0°F. Your supervisor needs you to determine the following items:

(a) The increase in entropy per lbm of R-134a flowing through the expansion valve.

(b) The entropy production rate per unit mass flow rate of R-134a flowing through the expansion valve.

(c) The average Joule-Thomson coefficient for this process.

Write and solve a thermodynamics problem to provide the answers.