Explanation:
The thermal or rational efficiency of the process is simply 2 kW/3kW = 66%. The second law efficiency takes into account the maximum efficiency possible for any system working between the two temperature limits; it is the quotient of the thermal efficiency and the Carnot efficiency. The Carnot efficiency in this case is 1 - 310/1200 = 0.74. Hence, the second-law efficiency for the process at hand is a remarkable 66/74 = 89%.
