Heat and mass coupled transfer combined with freezing process in building materials: Modeling and experimental verification

Abstract

Newly completed building envelope is always characterized by high initial moisture content, and so the liquid moisture permeability is the main feature of mass transferring on its initial use. The high initial moisture content has strong impact on indoor condition and energy consumption especially in severe cold area where the moisture freezing in building envelope would occur in winter. Therefore, accurately predicting the hygrothermal states of building envelope to obtain useful envelope parameters is very important. In order to analyze the moisture transferring performance of enclosure on building initial use in severe cold area, the paper studied the coupling transfer of heat and moisture in building envelope. The permeability and freezing of the liquid water in porous building material were considered. The moisture content gradient was used as mass transfer driving force, and the temperature gradient was used as heat transfer driving forces. Heat and moisture coupled transfer conservation equations on different transferring conditions were built. An experimental set-up was built to verify the model, and good agreements were obtained, which suggests that the model can be used to simulate the heat and moisture coupled transfer in newly completed building envelope of severe cold area.