Chapter 8, Problem 8.28P

In a 14 TR ammonia refrigeration plant, the condensing temperature is 250C and evaporating temperature -100C. The refrigerant ammonia is sub-cooled by 5 0C before passing through the throttle valve. The vapor leaving the evaporator is 0.97 dry. Find: 1. Coefficient of performance: and 2. Power required. Use refrigerant table for properties of ammonia at 250C and -100C.

b. A refrigerating system using Freon-12 has an evaporator saturation temperature of - 25°C and a condenser saturation temperature of 35°C. The vapor is dry saturated at entry to the compressor and has a temperature of 65°C after compression to the condenser pressure. There is no undercooling of the liquid in the condenser. i. Calculate the input power required by the compressor per kW of refrigeration. ii. Calculate the COPRef of the refrigerating system. ii. Show the operating cycle of the refrigerating system on a T-s diagram.

Calculate the logarithmic mean temperature difference for a condenser if the temperature difference between condensing steam and water inlet is 650oC and that steam inlet and water is 120oC.