Regeneration of heat and water from the exhaust air stream

This thesis deals with the process of wood drying. It is a method of removing excess water from wood. Drying can be divided into two basic types. The first type is natural drying. The material is dried without the presence of foreign energy source. This type depends only on climatic conditions and the amount of sunlight. Another type is artificial drying, where is pre-sent a foreign energy source, such as a biomass boiler. The second type is significantly faster than the first. The second type of drying uses a device called a wood dryer. There are a lot of types of wood dryers, the most widely used are kiln dryer, belt dryer, rotary drum dryer. In these devices, the thermal energy is transferred to the drying materials by the flowing warm drying medium (convection). The heat is transferred to the drying medium in a heat exchan-ger. Because the drying process is very energy demanding, it is appropriate to reduced the required energy. This can be done by regenerating heat and water. In the heat exchanger, part of the heat can be gained from the flowing exhaust medium. If a condensation of evaporated water in the exchanger occurs, the latent heat of the water is released. The gained heat is used to preheat the drying medium and thereby to reduce the required energy