DRYING PROMOTION OF AGRICULTURAL PRODUCTS USING CORONA DISCHARGE

电晕放电产生的离子风促进了农产品的干燥。他们说，离子风引起的强制对流导致了这种促进，然而，这并没有得到完美的解释。为了解释这一机理，分别采用有空气离子和无空气离子的强制对流进行了水分蒸发试验和萝卜干燥试验。前一种对流称为“带空气离子”对流，后一种称为“非空气离子”对流。两者都是由离子风制成的。此外，还对电晕放电干燥香菇进行了评价。非空气离子蒸发速率随电压线性增加，带空气离子蒸发速率随电压阶跃增加。在-4 ~ -10kV范围内，带空气离子的蒸发速率大于不带空气离子，在-10kV ~ -14 kV范围内，带空气离子的蒸发速率等于或低于不带空气离子的蒸发速率。在9.8kV下，有空气离子和无空气离子处理萝卜的干燥速率差异不大。空气离子对萝卜干燥的影响不大，但考虑到水分蒸发试验，应进行另一电压下的干燥试验。电晕放电后，与自然蒸发相比，水的蒸发速度有时会减慢。电晕放电使蒸发作用增强，潜热损失使水温下降。水温下降引起的热平衡变化似乎是造成蒸发迟缓的原因。在不同的实验条件下，电晕放电对香菇的干燥促进作用得到了认可，电晕放电法与常规方法的干燥速率之比为1.6 max。通过对干香菇的收缩率、色泽和吸水率的测定，发现电晕放电处理使干香菇的收缩率降低，色泽变黄，吸水率无变化。

Drying of agricultural products is promoted by ion wind from corona discharge. They say the forced convection caused by ion wind results this promotion, however, this is not explained perfectly. In order to explain this mechanism, the forced convection with air ion and that without air ion were used for water evaporation test and radish drying test. The former convection was called "with-air-ion" and the latter "non-air-ion". Both were made from ion wind. In addition drying of shiitake mushroom using corona discharge was evaluated.The evaporation rate using non-air-ion increased linearly with voltage, and that using with-air-ion increased in step. From -4 kV to -10 kV the evaporation rate using with-air-ion was higher than non-air-ion, and was equal to or lower than non-air-ion from -10kV to -14 kV.There were little difference between drying rate of radish using with-air-ion and non-air-ion at 9.8kV.It was appeared that the effect of air ion on radish drying was little, however, considering water evaporation test, drying test at another voltage should be performed.After corona discharge the evaporation rate of water was sometimes retarded in comparison with natural evaporation. The evaporation was enhanced under the corona discharge so that water temperature decreased owing to latent heat loss. It seems that the change of heat balance on account of water temperature drop caused the evaporation retardation.The drying promotion of shiitake mushroom using corona discharge was recognized under various experimental conditions The ratio of drying rate of corona discharge method to conventional method was 1.6 max. As a result of measurements of shirinkage, color and water absorption of dried shiitake mushroom, shrinkage decreased and color was little more yellow and absorption didn't change on account of using corona discharge.