Performance of cross-flow energy recovery ventilators with angled ribs

Energy recovery ventilators (ERVs) are widely used in building ventilation systems to improve energy efficiency by transferring heat and moisture between exhaust and incoming fresh air streams. In cross-flow membrane-based ERVs, performance is strongly influenced by channel geometry, which governs both heat and mass transfer and pressure drop. This study investigates the thermal–hydraulic performance of a modified cross-flow ERV incorporating angled ribs in the open channel to enhance heat and mass transfer. A combined numerical and experimental approach was employed to evaluate the effectiveness improvement and associated pressure drop penalty of the proposed geometry. Computational fluid dynamics (CFD) simulations were conducted to analyze the flow structure and local heat transfer behavior. The extracted heat transfer coefficients were implemented in a two-dimensional finite difference model (FDM) to predict sensible and latent effectiveness. The numerical method was validated for a full-scale exchanger using experimental measurements conducted under winter operating conditions. Good agreement was observed between numerical predictions and experimental results, particularly at mid-range flow rates, with an average absolute deviation of ±1.6%. Flow-field analysis of the CFD simulations revealed that the introduction of angled ribs generates secondary velocity components perpendicular to the primary flow direction, promoting enhanced mixing and boundary layer disruption. These rib-induced structures intensify with increasing Reynolds number, leading to higher convective heat transfer coefficients. In contrast to the simple open channel, where the Nusselt number remains nearly independent of Reynolds number in the fully developed region, the angled rib geometry exhibits increasing Nusselt number with Reynolds number. A linear regression correlation was developed to predict the Nusselt number for the modified configuration, enabling the determination of heat transfer coefficients at various Reynolds numbers and, consequently, the prediction of the exchanger’s sensible and latent effectiveness. Both numerical and experimental results consistently demonstrated an absolute improvement of approximately 4% in sensible and latent effectiveness with the addition of angled ribs. Although the modification increases pressure drop compared to the simple open channel, the hydraulic penalty remains significantly lower than that of conventional corrugated channels, indicating a favorable thermal–hydraulic trade-off.