Steady versus dynamic exergy analysis: the case of an air source heat pump

Abstract

Exergy analysis is often performed statically, for given system conditions and reference state. Dynamic exergy analyses, considering the variation of system operation and ambient conditions, would obviously be more time consuming. Therefore comparing the results of the two approaches helps understand when the dynamic methodology should be preferred. In this paper the yearly behaviour of a reversible Air Source Heat Pump (ASHP) is dynamically simulated with TRNSYS. At every time step the exergy delivered and consumed by the ASHP is calculated. Dynamic exergy efficiencies are then compared with steady state values and some useful considerations regarding the differences are performed.