Concerning exergy efficiency evaluation of heat recovery exchangers for air handling units

The energy chain of building energy services begins with primary energy resources and ends with building services systems (BSS). The analysis for such chain and its' elements should rely on fundamentals of thermodynamics. This paper pays attention to one of them that exergy efficiency is in the range of 0-1. In this study, exergy analysis of heat recovery exchangers for air handling units is carried out. Special attention is paid to the direction of thermal exergy flow when temperatures inducing heat transfer are close to a near-environmental temperature. On the basis of the proposed methodology, the dependency of exergy efficiency on dimensionless temperature and thermal recuperator efficiency is discussed. It is important to take the dimensionless temperature interval 0-1 into account. Here the exergy efficiency values are the lowest. Design and management measures should be used to avoid operating a heat exchanger there.