Limitations of the Carnot cycle for?

The Carnot Heat Engine Cycle and the Carnot Heat Pump Cycle are reversible cycles and do not exist in any actual operation. However, they are very useful

for predicting maximum possible thermal efficiencies and coefficients of performance using the absolute temperature of the heat source and the absolute temperature of the heat sink. The Carnot Cycle consists of two reversible and adiabatic ( isentropic ) steps and two reversible and isothermal steps.