Exergy analysis of CO2 heat pump systems

Abstract

Carbon dioxide (CO2, R744), a natural refrigerant of beneficial properties found everywhere in our ambiance, can provide answer to the environmental problems caused by other refrigerants' use. The intention of this work is to outline the variation of exergy efficiency factor, COP and exergy flow related to the use of CO2 in two stage and single stage heat pumps. The relevant mathematical models to the thermodynamic cycles were developed and an attempt was made for our efficiency and exergy losses results to be displayed. Moreover, fundamental process and system design issues of the applicable CO2 heat pumps cycles were inaugurated, along with their properties and characteristics, comparing CO2 use to that of R22 and its substitutes R407C and R410A applied in relevant conditions. Since exergy analysis is important theoretical basis for optimizing the systems operation and minimizing the losses, the results of this paper will advance the systems' design and performance.