Properties of Wet Gases, h-X Diagram

In vacuum drying, the released wet vapor is exhausted. In convection drying and other processes under normal or over-pressure, the moisture is carried away by an auxiliary gas, which is inert with respect to the solid. The gas flows over the product or penetrates through the product. Additionally, in convection drying, the gas is used as a heating medium whereby heat is transferred by convection to the wet product. 

The evaporated moisture contents in the wet auxiliary gas, the absolute moisture content or the moisture load X of the gas is 

Moisture movement by capillary force and surface force 

If a capillary of radius r is dipped into a wetting liquid, the liquid rises in the capillary by height z above the surrounding liquid level. 

The smaller the capillary the larger is z. Therefore, liquid is aspirated by narrow product capillaries from wider pores and transfered to the evaporation plane or product surface. The liquid flux w/, transported by capillary force is, according to Krischer 

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