Modeling and experimental validation in partially wet conditions of an air-to-air heat recovery exchanger

Nowadays, important efforts are deployed to reduce our current residential building consumption. The most common retrofit option concerns the air tightness and the thermal insulation improvement. However, this latter retrofit option could decrease the air indoor quality because of a reduction of air infiltration flow rate. Installation of an air-to-air heat recovery system allows for an efficient combination between consumption reduction due to the air tightness improvement and acceptable air indoor quality. The study presented in this paper has been realized in the frame of the ‘Green +’ project, which aims at developing decentralized heat recovery ventilation systems. The present paper focuses on modeling and experimental validation of an air-to-air heat recovery exchanger in partially wet conditions (i.e. where condensation might occur in one of the two air streams). The knowledge of the thermal performance in dry and wet regimes is essential since it highly impacts on the heat recovered from the vitiated air flow rate (extracted from the building) to the fresh air flow rate (coming from the outdoor). The first part of the paper briefly describes a solving procedure able to determine the regime (completely dry, completely wet and partially wet). A moving boundary model for the partially wet regime is applied in order to predict performance of such device.  Secondly, the experimental apparatus (and its control) designed to characterize thermal performance in different operating conditions (dry and wet regime) is presented. Thirdly, experimental data are presented and analyzed, which includes a comparison with simulation results.