The exergy efficiency assessment of heat recovery exchanger for air handling units, using a state property – Coenthalpy

Abstract

Exergy analysis is relevant to HVAC systems since both work and heat are present in the energy transformation processes. In this paper, an algorithm for the exergy analysis of a ventilation heat recovery exchanger (HRE) is proposed. It involves calculating exergy flows using coenthalpy as the state property. In exergy analysis, Borel considers coenthalpy k as direct potential of the exergy flow. As a result, universal and functional exergy efficiencies of a HRE are calculated. In any case, the solutions for exergy efficiency lie in the interval 0–1. The functional exergy efficiency proposed in the paper serves as the basis for determining the universal algorithm for the exergy analysis of a HRE at a varying reference environment temperature (RET). The values of these exergy efficiencies are discussed by numerical examples derived from the application of the developed algorithm. Functional exergy efficiency broadens the possibilities of increasing the exergy efficiency of processes taking place in HRE as well as allowing the application of exergy-optimal design and control of energy transformation processes in HVAC systems, the popularity of which is ever more increasing.