Abstract:

In this paper, the authors put forward the idea that the displacement flow in capillary structure under pressure gradient is the main mechanism of high intense and rapid drying process. In this paper, both analytical and experimental studies are carried out to clarify the displacement process and its characteristic. A simplified displacement flow model is proposed and the time of the moisture migration is calculated. A one-dimentional displacement flow test device is built up and a set of experiments under different pressure gradients and temperatures are conducted. Glass beads of 0. 8mm diameter are used as the porous material.
The experiment results show that under a constant temperature, as the pressure gradient is getting greater, the time for moisture to reach the external surface from the internal is getting smaller and the range of time reducing is getting smaller too. On the other hand, under the same pressure gradient, as the liquid temperature increases, the time for moisture from the internal to the external surface decreases.

Key words: rapid drying, porous media, displacement flow