Recent research suggests that fine-particulate air pollution increases the incidence of lung disease and pre-mature death. Single fibre filter theory is used to predict the theoretical particulate collection efficiency of air permeable walls (dynamic insulation). The relationship between particle diameter and filtration efficiency for dynamic insulation, as a function of flow rate, is examined and compared to that for a conventional filter.
The authors' previous analysis of dynamic insulation is extended to include the inner and outer air film resistances with the objective of modelling the variation in surface temperature with air flow. The boundary condition that comes closest to predicting the variation of the surface temperature with air flow is one which assumes that the conduction heat flux at the wall surface, rather than the net heat flux, is equal to the flux incident on the wall from global environmental temperature, T.;.
The concept of dynamic insulation, where cold air is drawn through porous insulation in a building envelope from outside to inside, thereby returning heat energy normally lost by conduction back into the interior of the building, has been studied by several researchers, in Japan, Europe and Canada. However the work to date has largely concentrated on the physical processes in individual wall, floor or roof elements and only a small number of experimental buildings (all of a small domestic scale) have been adequately monitored.
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