木材乾燥用温室システムに設置した潜熱蓄熱板の夜間保温効果および乾燥速度に及ぼす影響

摘要

To supply good quality domestic woods for house construction steadily, it is necessary to promote installation of wood drying system. In the case of kiln drying equipment, the energy consumption of drying becomes extremely high, while the drying period is short. To mitigate the global warming due to the exhaustion of CO2 from fossil fuels, the passive solar system for wood drying in an agricultural green house has been experimentally investigated. The installation cost of green house is low, but the following two points have to be improved to make the solar drying system for practical use:(1)the promotion of drying rate at nighttime, (2) the reduction of cracks appearing in wood with dry shrinkage at daytime. In the present study, the placement of phase change materials (PCM) in green house is proposed, and effects of PCM on air temperature rise at nighttime and drying rate are examined. The following results are obtained.(1)The air temperature in green house at nighttime increases due to the heat storage of PCM at daytime. The heat transfer between the air and PCM board in green house is affected by the arrangement of PCM board, and it is found that the vertical arrangement induces the improvement of heat transfer, which increases the heat storage of PCM and air temperature at nighttime. (2) In the constant drying rate period, the placement of PCM causes the decrease in the drying rate due to the decrease in the highest air temperature at daytime. In the falling drying rate period, the drying rate is increased by the increase in the air temperature at nighttime due to the heat storage of PCM.