Wood drying system using alternate hot dry and refrigerated humid air - using heat pump to control temp. of wood in drying enclosure and humidifying spray to control air moisture content

摘要

The drying of porous, fibrous, hygroscopic materials, such as wood, is performed without subjecting the material to high temps by initially storing the material in air at 25 to 35 degrees centigrade and 70 per cent humidity. After some days the temp. is raised to 60 degrees Centigrade and the humidity is lowered to about 30 percent, alternating with each heating cycle a cold humid period, the alternations becoming more frequent as the drying progresses. The material is stacked (2) inside a sealed enclosure (1) at one end of which is a heat pump unit (7) with its evaporator (8) and condensers (9,10) placed so the air is drawn by a fan (12) through the condenser (9) then past a humidifying water spray (18). The warmed moist air passes round the stack (2) and returns via the heat pump evaporator. A controller (14) operates a servo motor to vary the opening of a valve (15) which controls temp. by variation of the amount of air which bypasses the evaporator.