コンテナ内貨物の汗ぬれ現象-II : 結露量の経時変化

Abstract

In Japan, the amount of agricultural products imported from oversea has increased year after year. The cargo-container transportation plays an important role for the importation, but the sweat damages that occur during rapid cooling processes has been a serious problem for the transportation. The detail investigation for the sweat phenomena is necessary to solve the problem. Recently, we have successfully estimated the coefficients of the heat and vapor transfer by use of a miniature container loaded soybeans. In this paper, the heat and vapor transfer in a real-scale container, limiting the flows in the vertical direction, was simulated during cooling and then time-dependent change in the amount of dew was elucidated. The change of the temperature in the cargo indicates gradual release of heat in accordance with previous reports. The change of the vapor pressure shows the inversion of the flow direction, which had been observed in the measurement for a miniature container. On the other hand, the amount of dew on the ceiling, which is strongly related to the sweat damages, showed a maximum and disappeared within about 5 days. The maximum weights, 0.17-0.02kg/m^2, are considerably little and hence the dew would not drop without any vibration and shock of the container. Therefore, it concludes that the keeping the container in static conditions for 1-4 days prevents the cargo from suffering the sweat damages.