1. Refrigerant R134a enters a counterflow heat exchanger operating at steady state at -20C and a quality (kuruluk) of 35% and exits as saturated vapor at -20C. Air enters as a separate stream with a mass flow rate of 4 kg/s and is cooled at a constant pressure of 1 bar from 300 to 260 K. Heat transfer between the heat exchanger and surroundings can be ignored, as can all changes in KE and PE. Let To = 300 K and Po = 1 bar. Answer the following cases: (12%) (a) Sketch the variation of temperature with position of each stream in the heat exchanger on the same diagram. Additionaly sketch; on a P-T diagram for air from inlet to exit, and on a T-S diagram for R-134a fluid from inlet to exit. Also, place Po , To and relevant stream pressures on P-T and T-S diagram sketches. (12%) (b) Calculate refrigerant mass rate. (15%) (c) Determine the rate of available energy destruction within the heat exchanger in kW. (11%) (d) Devise and evaluate an available energy efficiency for the heat exchanger.