Mathematical modeling of gas-phase mass transfer in hydrous materials for a total heat exchange ventilator

Abstract

Total heat exchange ventilation systems are effective in achieving energy savings by reducing the ventilation load in buildings, while maintaining a certain amount of fresh outdoor air intake. As the system's elemental materials exchange both latent and sensible heat, hydrophilic chemical compounds may be exchanged simultaneously. Proper control of the exchange of hazardous chemicals and pollutants via these heat exchange elements is an important issue in the development of total heat exchange ventilation systems. In this respect, the development of a numerical model that facilitates repeated sensitivity analysis is important in the development of a new total heat exchanger that has high heat exchange efficiency and suppresses the exchange of polluting chemicals. This study proposes new hygrothermal and chemical compound transfer models for paper-based hydrous materials, which are the main components of total heat exchangers in indoor ventilation systems. Through a series of numerical analyses and experimental measurements, the prediction accuracy of the mathematical model was compared with experimental results for the gas transfer rate in hydrous materials and a building-sized total heat exchanger. The results demonstrated that an increase in water content in hydrous material has a significant impact on the permeability of water-soluble gases, with NH₃ and HCHO permeability coefficients increasing by factors of 250 and 20 respectively. Conversely, for low-solubility gases such as CO₂, the permeability coefficient only slightly increased at low humidity and remained largely unaffected thereafter. These findings contribute to the advancement of more efficient and safer total heat exchange ventilation systems.