1. A piston cylinder device contains 0.5 kg of R - 134a at 500 kPa and 80 C . The refrigerant is now cooled at constant pressure until it exists as a saturated liquid - vapor mixture

( x = 0.4 ) at 20 C . a )

Determine the entropy change of the R - 134a during this process . ( Answer : -0.28 kJ / K ) b ) Sketch a T - s diagram with respect to the saturation line for this process .

2. An insulated piston - cylinder device equipped with an electric resistance heater contains 5 L of saturated liquid water at 150 kPa . 2200 kJ of energy from the electric resistance heater is isobarically transferred to the steam .

a ) Determine the entropy change , in kJ / K , of the water during this process . ( Answer : 5.72 kJ / K ) .

b ) Sketch a T - s diagram with respect to the saturation line for this process .

1. A piston cylinder device contains 0.5 kg of R-134a at 500 kPa and 80 C. The refrigerant is now cooled at constant pressure until it exists as a saturated liquid-vapor mixture (x = 0.4) at 20 C. a) Determine the entropy change of the R-134a during this process. (Answer: -0.28 kJ/K) b) Sketch a T-s diagram with respect to the saturation line for this process. 2. An insulated piston-cylinder device equipped with an electric resistance heater contains 5 L of saturated liquid water at 150 kPa. 2200 kJ of energy from the electric resistance heater is isobarically transferred to the steam. a) Determine the entropy change, in kJ/K, of the water during this process. (Answer: 5.72 KJ/K). b) Sketch a T-s diagram with respect to the saturation line for this process