(a) Isentropic efficiency describes the thermal efficiency of heat engine in converting thermal energyto mechanical work. An isentropic efficiency of 90% indicates that the heat engine can convert 90%of thermal

energy received from hot thermal reservoir to mechanical work. (b) Isentropic efficiency is a function of temperature of hot and cool thermal reservoir. (c) The isentropic efficiency of a reversible cycle is 100%, which does not violate the Kelvin-Planckstatement of the 2nd Law. (d) Isentropic efficiency is defined as a parameter indicating the extent of excellence of an actualprocess when compared to isentropic process. An isentropic efficiency 90% of a heat engine indicates that work produced by this heat engine is 90% of that of an isentropic engine operated withthe same two thermal reservoirs and the consumption of the same amount of thermal energy. (e) Isentropic efficiency indicates the extent of irreversibility involved in an actual cycle. The higherthe isentropic efficiency, the less the irreversibility.