Two carnot-cycle heat engines (A and B) work in series. Engine A absorbs heat at 627 oC from a high temperature thermal reservoir and releases heat to a thermal reservoir at temperature T; Engine B absorbs the heat released by Engine A at temperature T and releases heat to ambient air of 27 oC. Determining temperature T at the following conditions: (a) the work outputs of both engines are equal and (b)the thermal efficiencies of both engines are equal.
A refrigerator with a coefficient of performance of 4 transfers heat from a cold region at -20ºC to a hot region at 30ºC. Calculate the total entropy change of the regions when 1 kJ of heat is transferred from the cold region. Is the second law satisfied? Will this refrigerator still satisfy the second law if its coefficient of performance is 6?