modelling

This report presents a simplified computational model for combined air-, moisture and heat transport for one-dimensional cases. The model is based on finite difference technique with explicit forward differences in time. Analytical solutions for the coupling, the conductances, between the computational cells for a given air flow through the construction are used. Moisture is transferred by vapour diffusion and vapour convection. No liquid water transport occurs.

A numerical model, employing a local-averaging formulation was developed for heat transfer and water vapor deposition within fiberglass insulation under air exfiltration and frosting conditions. Frost growth on the cold surface was modeled using special frost growth boundary conditions. Non-isotropic permeability effects that occur in fiberglass boards were included in the mode/for porous medium flow because tests showed that the permeability for flow parallel to the plane of the boards was 69% higher than perpendicular to the insulation boards.

A new parametrical model for the prediction of the thermal performance of the earth to air heat exchangers is presen1ed. The system consists of an earth tube, buried in the ground, through which ambient or indoor air is propelled and cooled by the bulk temperature of the natural ground. The proposed model has been developed by analysing temperature data of the circulated air at the pipe's outlet using a systematic parametrical process.

Mathematical models have been used by various researchers to provide both a fundamental understanding of indoor air quality dynamics and a platform for estimation of IAQ constituents in lieu of experimental measurements. Due to the diverse nature of these applications the complexity and hence applicability and accuracy of the models varies tremendously. Some models have been specifically developed for evaluation of the impact of a broad range of environmental conditions on IAQ constituents.