Abstract
A transient method to determine the moisture diffusion coefficient of material is described. The experimental procedure is to suspend a sheet of the material in the atmosphere at constant temperature and humidity, and to observe any increase in material weight. Mathematical model in the method is derived by using the following assumptions. (1) The material is semi-infinite solid. (2) Surface humidity is equal to air humidity. In other words moisture transfer coefficient is sufficiently large. (3) Interaction between moisture and heat in the material is negligible. These assumptions cause measuring errors in applying this method to building material. In this paper, emphasis is on the mathematical analysis of errors. Errors are analyzed by means of Laplace transformation method. Errors caused by each assumption are shown in a graph. Experimental conditions, i. e. sheet thickness and data length, which assure measurement accuracy, are derived from the graphs.
