Study on characteristics of moisture diffusion in multi-layer paper insulation

摘要

In this paper, a mathematical model was set based on mass diffusion laws to simulate the moisture diffusion process in paper insulation. Besides, we designed 3 kinds of paper models with different paper layers and experimentally investigated the moisture distribution in the direction of thickness of paper and its variation with time. Each layer of paper insulation was sampled in enclosed spaces and the corresponding moisture content was detected by Karl Fischer titration. It was found that the migration speed had positive correlations with the gradient of local moisture content, which was in accordance with the law introduced in the model. Furthermore, the influence of temperature on moisture distribution and the diffusion speed were experimentally studied. The experimental data was discretized and fitted into the discretion model. The characteristic coefficients in the model were obtained by solving the discrete model. The relations between diffusion coefficients and temperature with moisture content were acquired. Finally, relations between the number of paper layers and diffusion speed were investigated on designed models through experiments. It was indicated that the differences in relevant coefficients among different models were obvious. The diffusion speed of moisture decreased with increasing number of paper layers. We considered that the layer effect was aroused by micro oil gap between paper layers.