Experimental investigation of condensation in energy recovery ventilators

Abstract

Membrane-based Energy Recovery Ventilators (ERV) have become an important part of modern ventilation systems for commercial and residential buildings due to their high sensible and latent effectiveness. Using ERVs in winter conditions, however, can result in condensation and frost formation. Whereas frost formation requires extremely low temperatures, condensation can occur even in mild winter weather conditions. In this study, a widely used ERV is experimentally tested under various indoor and outdoor operating conditions. Short time tests are used to determine the onset of condensation while long time tests are used to investigate the effect of channel blockage due to condensation on pressure drop and effectiveness of the ERV. The presence of condensation is inferred from visual observation of water in the exchanger, investigation of the sensible and latent effectiveness, and measurements of pressure drop over the exchanger. It is shown that condensation increases the sensible effectiveness of the supply side and decreases the sensible effectiveness of the exhaust side. Additionally, the latent effectiveness of both air streams increases when condensation occurs, although the increase in exhaust side latent effectiveness is more significant. Increasing the relative humidity and temperature of the indoor air increases the possibility of condensation and its rate, while increasing flowrate only increases the rate of condensation and does not affect its onset. Finally, the accumulation of water in the channels significantly increases the pressure drop in the exhaust side while it does not significantly impact the effectiveness.