A
vacuum drying system is being designed and developed at National Institute of
Vacuum Science & Technology (NINVAST) to dry various materials under vacuum
conditions. Its performance and capabilities are tested by carrying out
different experiments on green (freshly cut) wood samples of Poplar and
Eucalyptus with dimensions of 990.6 mm x 76.2 mm x 25.4 mm and 469.9 mm x 50.8
mm x 25.4 mm, respectively. These samples were dried from green moisture
content (MC) 78% to 10% by this system at ultimate vacuum of about 1.6 x 103
pascal and at a temperature ranging from 35oC to 55oC for
about 20 hrs. Drying quality tests included: prong test, warp measurement,
surface checking and moisture content measurement, which were all performed.
The resulting wood samples showed no dislocation and no excessive stress
buildup. If compared to ordinary drying process, the vacuum drying is rapid and
the drying rate increases with rise in temperature. The designed system is
beneficial for commercial use.
