3D Flow Simulations of Fan Enclosure Concepts for a Novel Heat and Moisture Exchanger

Abstract As the single most energy-intensive system in buildings, heating, ventilation, and air conditioning (HVAC) units consume on average 40 percent of total building energy in the United States. For regions with hot and humid climates, building loads due to HVAC systems increase significantly as a large portion of the electric load is used to condense moisture in the air. To improve building energy efficiency, energy recovery ventilators (ERV) have played an increasingly important role. They essentially rely on a membrane-based heat and moisture exchanger (HME) to reduce the latent heat load. A novel energy recovery ventilator was recently developed to improve ERV performance and advance building design. It combines a HME, two impeller fans and air enclosures into a single unit. In this work, two enclosure concepts were investigated, both of which have each fan placed in the enclosure of the HME inlet. Computational fluid dynamics (CFD) was used to model air flow inside the enclosure. The simulation results provided important information on the distribution of air flow across the inlets of the HME, which is expected to improve the enclosure design to meet the ERV performance target. A grid refinement study was conducted which showed that the medium grid refinement produced results within 3% of the asymptotic solution and had significantly less computation time compared to the fine grid. The first concept had a velocity uniformity of 86% at the HME inlet, while the second concept showed undesirable, reversed flow in the upper channels. The study indicates placing the fan at the outlet of the HME, rather than the inlet, would lead to more uniform air flow into the HME.