Steady-state and unsteady-state moisture regime of enclosing structure

Abstract

This paper describes the moisture transfer problems of enclosing structures which are crucial in modern construction industry. In terms of current condition of science, researchers do not know the moisture transfer law in capillary-porous materials, so they need to work with a variety of mathematical models. We developed the new steady-state and unsteady-state formulation of mathematical models based on moisture potential F, which takes into account water vapour and liquid movements uniformly. It is vital to understand whether we can use steady-state moisture transfer mathematical model in a design engineer work or we must use the unsteady-state one, so we make a comparison between them for a single-layer aerated concrete wall. We compare moisture behaviours of the steady-state and unsteady-state processes in two ways: comparison of the moisture distribution in the thickness of the enclosing structure during maximum moisture accumulation period and comparison of the average moisture of the wall during a year. It was found that the solution of the unsteady-state equation of moisture transfer gives significantly more possibilities than the solution of the steady-state equation of moisture transfer. As a result, we recommend to use the developing unsteady-state mathematical model to predict the moisture regime of enclosing structures.