Finite Time Thermodynamic Analysis of an Internally Irreversible Heat Engine-Driven-Heat Pump System Utilizing Low Grade Thermal Energy

A Rankine cycle heat engine utilizing low grade thermal energy is used to drive a conventional mechanical compression heat pump, providing heating and cooling loads. The performance of such a system is first modeled using an endoreversible analysis where only external irreversibilities exist due to the heat transfer between the system and surrounding thermal reservoirs. This approach is extended further to the analysis of a system where irreversibilities are both external, associated with the heat transfer, and internal to the cycle, due to the compression and expansion processes. A cycle irreversibility parameter is used to characterize the extent of internal irreversibility. This approach provides more realistic upper bounds for the performance of such a device and information regarding optimum working fluid temperatures.