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Spontaneous imbibition plays a significant role in different technical applications, and several analytical models have been proposed for predicting the fluid imbibition mass into porous media based on the fractal theory. Herein, these previous models are reconsidered in view of the obvious difference between the effective porosity and the areal porosity of porous media. Firstly, an implicit equation for fractal tortuosity is proposed and a modified correlation for the areal porosity is presented; then, a semi-analytical prediction model for fluid imbibition mass with gravity pressure is derived; finally, comparisons of predictions among several previous models with the present model are carried out. The modeling results show consistency with the experimental data published in the literature.

In order to improve the comprehensive performance of solid adsorption desiccant for compressed air adsorption dryer and reduce the loss rate of adsorption dryer, a new type of binary composite solid adsorption material suitable for compressed air drying is put forward. This material is composed of activated alumina (matrix) and 4A molecular sieve and 13X molecular sieve respectively in the proportions of 95%/5%, 90%/10% and 85%/15%. Static characteristic analysis is first made on three macro characteristic parameters, including the compressive strength, specific surface area and static water adsorption (60%RH). Thereafter, microscopic surface morphology analysis on composite material samples are employed. Comparative analysis result shows that, for compressed air drying, the activated alumina/13x molecular sieve with the proportion of 85%/15% is better than the 90%/10% activated alumina/4A molecular sieve composite solid adsorption material.