Investigation of the Effect of Non-Uniform Membrane Properties on Performance of Mini/Microchannel Energy Recovery Ventilator Devices

Abstract

Membrane based energy recovery ventilators (ERV) can be used to recover sensible and latent energy from exhaust-to-supply air in building applications. These typically consist of parallel layers of membrane separating the air streams, across which heat and moisture are exchanged. Reducing equipment cost and size remain a key challenge for continued commercialization and adoption of these devices. As membrane effectiveness improves, the air-side heat resistance can begin to dominate transport. To mitigate this, minichannel flow passages (DH < 2 mm) can be used to reduce convective heat and mass transfer. Channels can be formed through direct manipulation of membrane (e.g., pleating, corrugating, etc.), or through the use of spacer or other insert. The use of multiple parallel channels can result in large spatial variations in driving temperature and humidity ratio differences in a single layer membrane, impacting overall transport. Furthermore, the local membrane mass transfer resistance is typically a function of the surface temperature and relative humidity and not a constant value throughout the device. Accurate design models are required to appropriately size ERV equipment and maximize performance for a given equipment volume. Thus, the goal of this study is to use simulation tools to understand how the use of parallel mini- and microchannels and non-uniform membrane properties effect the performance of a membrane ERV in a building application. A two dimensional coupled heat and mass transfer resistance network model is developed. The model is compared against existing data from more detailed CFD analysis, and used to parametrically investigate effects different inlet conditions on device performance.