Gaseous Contaminant Transfer in Membrane Energy Exchangers
Date
2023-09-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Membrane-based air-to-air energy exchangers (M-AAEEs) reduce the energy required for conditioning building ventilation air by transferring heat and moisture between the building exhaust and ventilation air. However, M-AAEEs may also contaminate the ventilation air due to the transfer of contaminants from the stale exhaust air leaving the building to the fresh ventilation air being supplied to the building. It is important to quantify this transfer to assess its impact on indoor air quality. Hence, the main objective of this thesis is to quantify contaminant transfer in M-AAEEs using test methods available in the literature.
A test facility was developed, and experiments were performed to quantify the contaminant transfer for different air flow rates, pressure conditions, contaminants and membrane types. Contaminant transfer was quantified using a parameter called the exhaust contaminant transfer ratio (ECTR), which gives the fraction of the contaminants that transferred from the exhaust air to the ventilation air. Furthermore, a theoretical model was developed to predict contaminant transfer through the membranes. The results from the experiments and the theory were in good agreement within uncertainty limits. The experimental uncertainty in ECTR was between ± 0.5% and ± 2.7%.
Contaminants with lower molecular weight and smaller size (i.e., higher diffusivity) tend to have higher transfer through the membranes considered in this study. As a result, the inert tracer gas test, which is recommended in current energy exchanger standards to determine leakage in M-AEEs, may not represent the transfer of many common indoor contaminants. Moreover, the theoretical model presented in this study can be used to estimate contaminant transfer if the moisture transfer rate through the membrane is known.
Description
Keywords
Membrane-based air-to-air energy exchanger (M-AAEE), contaminant, Exhaust air transfer ratio, Membranes
Citation
Degree
Master of Science (M.Sc.)
Department
Mechanical Engineering
Program
Mechanical Engineering