Odour transfer in membrane energy exchangers for ventilation: An investigation on sensory perception and design implications

Abstract

Membrane energy exchangers (MEEs) are increasingly utilized for their ability to maintain adequate ventilation rates that ensure good indoor air quality in an energy efficient manner. Their capability to transfer moisture reduces humidity loads in hot, humid climates and prevents frost formation inside heat exchangers in cold climates. Nevertheless, odour transfer through semi-permeable membranes has been largely overlooked assuming negligible effect without robust scientific evidence. Recent studies have revealed that the commonly used tracer gas method for heat recovery systems is inadequate for assessing odour transfer in MEEs. This study developed three MEEs using additive manufacturing. While maintaining identical dimensions, the MEEs incorporated different membranes with distinct pore sizes and moisture transfer abilities. Untrained sensory panels, comprising 20–25 participants, assessed odour perception in a laboratory environment. Six representative odour sources commonly encountered in real-world scenarios, along with three blank controls, were evaluated. The results show that high-intensity odours, such as salami, posed significant challenges for all tested MEEs, with dissatisfaction rates ranging from 72 % to 95 %. MEE-1, with the highest humidity transfer resistance (143.3 s/m), demonstrated the best odour mitigation performance. The other two MEEs showed comparable sensory outcomes despite MEE-2′s higher humidity transfer resistance. No consistent correlation was identified between moisture transfer resistance and odour transfer resistance, indicating that odour selectivity cannot be reliably benchmarked based solely on moisture transfer properties. These findings highlight the need for further investigation into the factors influencing odour transfer and the importance of tailoring MEE designs for specific odour profiles.