What is the drying process?

The drying process is the controlled removal of moisture or liquid from a material through evaporation, and it involves both heat and mass transfer. In its simplest form, heat is supplied to the wet material, which provides energy to convert liquid water into water vapor, and then moving air carries that vapor away from the surface. In industrial drying theory, the process is divided into stages. First, the material is heated up to the wet bulb temperature while free surface water evaporates at a constant rate. Second, as surface water is depleted, moisture must migrate from inside the material to the surface, causing the drying rate to fall and the material temperature to rise. Third, in the final falling rate period, the surface is dry and internal diffusion controls drying, making it much slower until equilibrium moisture content is reached. Methods to achieve this include air drying, sun drying, convection drying in ovens, conduction drying on hot surfaces, radiation drying with infrared or microwaves, freeze drying by sublimation under vacuum, and desiccant drying using materials that absorb moisture. In laundry, the drying process means spinning out bulk water, then evaporating remaining moisture with warm air circulation. In building restoration after water damage, it involves extracting standing water, then using dehumidifiers and air movers to dry porous materials like drywall and wood within 24 to 72 hours to prevent mold growth.