R-134a is expanded in an expansion valve or trap from an inlet state of 50 C (saturated liquid) to a pressure of 0.2 MPa. If the heat transfer rate to or from the valve is negligible (there is no work done either), what is the temperature of the refrigerant at the exit

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2