1. The performance of an ammonia absorption cycle refrigerator is to be compared with that of a similar vapor-compression system. Consider an absorption system having an evaporator temperature of -10?C and a condenser temperature of 50?C. The generator temperature in this system is 150?C. In this cycle, 0.42 kJ is transferred to the ammonia in the evaporator for each kilojoule transferred from the high-temperature source to the ammonia solution in the generator. To make the comparison, assume that a reservoir is available at 150?C, and that heat is transferred from this reservoir to a reversible engine that rejects heat to the surroundings at 25?C. This work is then used to drive an ideal vapor-compression system with ammonia as the refrigerant. Compare the amount of refrigeration that can be achieved per kilojoule from the high-temperature source with the 0.42 kJ that can be achieved in the absorption system.
2. If we neglect the external irreversibilities due to the heat transfers over finite temperature differences in a power plant, how would you define its second-law efficiency?