Improving performance of AHU using exhaust air potential by applying exergy analysis

Abstract

In this study, the exergy analysis of an AHU equipped with a heat and exergy recovery unit was investigated. The equations obtained from energy and exergy balance were solved based on a program developed in engineering equation solver. Through the air-to-air heat exchanger, the energy is transferred from the fresh air to the exhaust one but the exergy is transferred from the exhaust air to the fresh one. Therefore, the cooling coil power consumption and irreversibility were reduced. The efficacy of installing an air-to-air heat exchanger is dependent on the temperature and relative humidity of the ambient. Based on the results, at the lowest ambient temperature and relative humidity, the power consumption is reduced by 10.8%, while in the highest ambient temperature and relative humidity, this figure was 33%. Under ambient conditions with low temperatures and high relative humidity, installation of heat recovery unit reduced the irreversibility by 5.18%, while in the highest temperature and lowest relative humidity this figure was 12.8%.