Vacuum drying kiln

摘要

A vacuum drying kiln has a drying chamber in which, in use, is placed timber to be dried and around which is a surrounding water jacket through which is circulated a heat exchange fluid which derives its heat by flowing through the secondary circuit of a heat exchanger through the primary circuit of which is pumped a mixture of air and water vapor drawn by a vacuum pump from the interior of the drying chamber. The kiln is operated cyclically through successive heating and evacuation phases and the vacuum pump is one utilizing a secondary fluid to effect pumping, the characteristics of this secondary fluid being that it is immiscible with water and has a low specific heat so that it encourages the condensation of the water vapor in the primary circuit of the heat exchanger by undergoing large temperature variations for small changes in heat content.