Design And Use Of The Hybrid Drying Equipment With High Frequency Heating And Hot-air For Wood

Hybrid drying with High Frequency (HF) heating and hot-air for wood, an international advanced technology, was newly introduced from Japan by Northeast Forestry University and it will play an important role in drying hard-drying wood, large section wood and so on. The key to promote the technology and improve the level of domestic wood drying technology is how to change domestic conventional drying equipment into hybrid drying equipment with High Frequency (HF) heating and hot-air for wood and the fair use of it. In this research, the method to calculate the power and frequency for the high-frequency generator in the above mentioned hybrid drying equipment and the determination of the parameter for the adequate high-frequency generator were explored; the conventional drying kiln combined additional high-frequency generator was designed and the testing machine for the pilot plant test was made; the match between high-frequency heating and convection heating during the combined HF and convective heating (dual heat source heating) stage of wood drying with the testing machine was preliminarily studied by using larch as experimental specimen. The contents and results were as follows:1 The method to calculate the required high-frequency power for wood heating and water evaporating during the high-frequency heating process was explored. The high-frequency power of each stage by the percentage of high-frequency heating was calculated in order to determine the high-frequency power of the high-frequency generator in the dual heat source heating wood drying equipment. In addition, the method to determine the frequency of the high-frequency generator based on the length of wood was explored in order to insure the heating uniformity and heating efficiency. Based on these studies, the example of the selection for the high-frequency generator was given.2 The pilot plant test equipment of hybrid drying with High Frequency (HF) heating and hot-air for wood which is suitable for domestic use was designed, including design of the conventional convection heating drying device, the HF heating device and the device for HF long-distance transmission to four plies'circular heating by one high-frequency generator.3 The match between high frequency heating and convection heating during wood drying process was preliminarily discussed. The results showed that the time of high-frequency heating had little effect on the total drying time; with the method of convective heating in the first and second drying stage, the high frequency heating in the third stage especially below 20% moisture content, the surface checks were reduced with good drying qualiy, and lower power consumption.