Applicability of Comsol Multiphysics to Combined Heat, Air and Moisture Transfer Modelling in Building Envelopes

摘要

The intention of this project is to analyse the applicability of the programme Comsol Multiphysics for the study of different physics in building envelopes regarding the laboratory tests and other program, WUFI, in order to check its reliability. The laboratory tests and the WUFI’s simulations were performed within the framework of a previous project carried out at the Civil Engineering Department at Tampere Universiy of Technology.Two different types of simulations have been performed to accomplish the purpose: only diffusion and the combination of diffusion and convection. Ten structures have been used in the diffusion simulations and another different one has been chosen for the second simulation. All the structures used are building envelopes made of different construction materials such as gypsum board, spruce plywood, fiberglass, rock wool or flax insulation among others.Several Comsol’s modules have been tried before finding the correct ones, the “Free and Porous Media Flow” interface within the “Fluid Flow” module for the air transfer and the “Coefficient form PDE” interface within the “Mathematics” module for the coupled heat and moisture transfer.The results of Comsol are more similar the laboratory results than the WUFI’s results are in general. However, the results are not enough satisfactory which means that the differential equations are not enough even applied with Comsol whose numerical techniques are better. Those equations contain simplifications that can be the reason of the lack of accuracy, such as the Fickian transport.