Emerging Technologies: Air-To-Air Energy Recovery Heat Exchangers PDF

This is the sixth article covering a new energy-saving technology evaluated in a recent U.S. Department of Energy report, which is available at www.eren.doe.gov/buildings/documents.

Air-to-air energy recovery heat exchangers (ERHXs) include heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs). They are placed in ventilation units, unitary air conditioners, and air-handling units that take in outdoor air (OA) while venting indoor air (Figure 1). Exhaust air from the building interior passes through one side of the exchanger, counter flow to the incoming makeup air, which passes through the other side of the exchanger. During the cooling season, the (cooler) indoor air precools the incoming OA. The transfer of heat reverses during the heating season, i.e., the exchanger transfers heat from the warmer indoor air to preheat the incoming OA. The heat exchanger may transfer sensible heat only (HRV) or both sensible and latent heat (ERV). Typical heat and enthalpy exchange efficiencies range from 55% to almost 80%.¹ ARI Standard 1060 and ASHRAE Standard 84 form the basis for rigorous performance ratings of ERHXs.