轻质稻秸保温材料高频热压板坯内部温度的研究

Study on Internal Temperature of Rice Straw Insulation Board during High-frequency Hot Pressing

研究了高频电场中板坯厚度方向温度分布规律以及制板工艺因素(包括原料含水率、板材厚度和板材密度)对轻质稻秸保温材料板坯内部温度的影响,试验采用荧光光纤温度测定仪自动准确测定高频热压时板坯内部温度。结果表明:板坯升温过程分为快速升温、水分排出、慢速升温三个阶段,板坯内部温度在厚度上存在差异.温度分布总体表现为芯层高表层低。与常规热压相比,高频热压大大缩短了热压时间,且板坯厚度方向温度均匀性大大优于常规热压。在快速升温阶段,在一定范围内提高含水率能加快板坯的升温速度;在水分排出阶段,通过减小原料含水率能缩短水分汽化时间;原料含水率对慢速升温阶段基本没有影响。在整个升温阶段,板材密度越低,其升温速度越快;在水分排出阶段。板材密度越低,水分汽化时间越短。板材厚度的影响作用与板材密度类似。

The rule of temperature distribution with thickness by high-frequency hot pressing was investigated.The effects of moisture content （MC）,board density and thickness on internal temperature of rice straw insulation material were evaluated as well.A temperature detector of fluorescence optical fiber was used to measure the internal temperature of mats automatically and accurately during high frequency hot-pressing.The results show that the temperature-time curve can be divided into three stages：a rapidly temperature rising stage,a water evaporating stage and a slowly temperature increasing stage.The internal temperature changes cross the thickness section.Normally,the temperature of the central layer is higher than that of the surface layer.Comparing with the conventional hot pressing,the pressing time can be greatly shortened by high-frequency hot pressing.Meanwhile,the internal temperature is more uniform in the mat thickness direction.In the rapidly temperature rising stage,the internal temperature is increased dramatically with raising the moisture content.In the moisture vaporizing stage,the time can be shortened by decreasing the moisture content.The moisture content has no influence on the slowly temperature increasing stage.The lower density of boards promotes the increase of the temperature and the decrease of the time of water evaporation.The influence of the board thickness on the internal temperature is similar to the board density.