Development of hybrid kiln drying system with radio frequency heating for the sugi boxed heart timber

In this study, proper applied stage of the radio-frequency (RF) heating during kiln drying based on the quality concerning the surface checks of the boxed heart timbers was examined. At the stage of the RF heating the moisture contents decreased clearly at the internal parts of timbers. The surface stress of the sugi (Cryptomeria japonica D. Don) boxed heart timber changed into the compression stress by the RF heating in any drying stage. The surface checks increased according to the decrease of the moisture content. However, the increase of the area and the width of the surface checks in the Link 3 were comparatively low, and the quality of these boxed heart timbers seemed relatively good. The amount of electric energy of RF heating in the Link 3 was fewer than that in the Link 1, 2.