is used to superheat the vapor entering the compressor while subcooling the liquid leaving the condenser. The system uses R-134a. The evaporator operates at 15oF and the condenser operates at 100 psia. The heat exchanger provides 40oF of subcooling at the throttle valve entrance. a) Calculate the entropy generation at the throttle for the simple refrigeration cycle. Calculate also the entropy generation of the universe (throttle + surroundings) due to this operation. b) Calculate the process efficiency of the heat exchanger for the refrigeration cycle that includes the heat exchanger

ercise 6 6.1 A surface condenser is fitted with separate air and condensate outlets. A portion of the cooling surface is screened from the incoming steam and the air is passes over these screened tubes to the air extraction and becomes cooled below the condensate temperature. The condenser receives 20 000kg/hr of dry saturated steam at 36.2°C. At the condensate outlet the temperature is 34.6°C TK and at the air extraction the temperature is 29°C. The volume of air and vapour leaving the condenser is 3.8m3/min. Assume constant pressure throughout the condenser, calculate: 6.1.1 the mass of air removed per 10 000kg of steam (2.63kg); 6.1.2 the mass of steam condensed in the air cooler per minute (0.5kg/min)%3B 6.1.3 the heat rejected to the cooling water (13451kW).

The evaporator (a heat exchanger) in an A/C unit has R-410A entering at -20 °C and a quality of 30% and leaves at the same temperature and a quality of 100%. The COP of the air conditioner is known to be 1.3 and the mass flow rate is given as 0.013 kg/s. Find the power input to the cycle. (Note that, here, the evaporator is the part of the A/C unit that accepts [i.e., withdraws] heat from the room maintained at a cold temperature)