EXPERIMENTAL STUDY ON HEAT TRANSFER ON AND UNDER GROUND CONSIDERED MOISTURE MOVEMENT

对地面垂直温度分布和地表热通量进行了为期两年的长期观测。地面上覆盖着五种不同的材料；裸土、草坪、混凝土路面、沥青路面及透水沥青路面。观测包括天气和土壤含水量的数据采集。长期观测结果表明，夏季混凝土和沥青路面日平均温度均在40ºC以上。裸露土和草坪在同一季节的日平均表面温度比混凝土和沥青路面低7 ~ 10‰。裸露土和80cm深度草坪的地下温度全年都比混凝土和沥青路面的地下温度低3 ~ 5ºC。混凝土和沥青路面下的土壤含水量很高，这是由于抑制了水的蒸发。根据含水量的变化，测定了土壤的导热系数、体积比热和电阻。土壤在湿润条件下的导热系数是干燥条件下的两倍大。研究了两种类型的模拟模型来预测地面的热性能。一种方法精确地考虑了地下水分的运动，而另一种方法仅仅考虑了地表水分蒸发的影响。在前一种模拟模型（称为模型A）中，土壤中的水分随含水量的梯度而变化，土壤的热性质也随含水量的变化而变化。后一种模型称为模型B，它使用蒸发比计算水在表面的蒸发量，并且热性质是恒定的。实测值与计算值的比较表明，对于地表和地下的再生换热现象，A模型比B模型更准确。然而，模型B有足够的精度来预测地上和地下的热量传递。少

Long-term Observation of vertical temperature distribution and surface heat flux of the ground has been carried out through two years. The ground is covered with five different kind of materials; bare soil, lawn, concrete pavement, asphalt pavement and permeable asphalt pavement. The Observation includes the data acquisition of weather and water content of soil.The results of the long-term Observation show the daily average surface temperatures of the the concrete and the asphalt pavement are over 40ﾟC in summer. The daily average surface temperatures of the bare soil and the lawn are lower than those of the concrete and the asphalt pavement by from 7 to 10ﾟC in the same season. The underground temperatures of the bare soil and the lawn at the depth of 80cm are always lower than those of the concrete and the asphalt pavement by from 3 to 5ﾟC through a year. The water content of the soil under the concrete and the asphalt pavement is high because of the suppression of water evaporation … More at the surface.The thermal conductivity, volumetric specific heat and electric resistance of the soil were measured according to the variation of the water content. The thermal conductivity of the soil under wet condition has as two times large value as that under dry condition.Two types of simulation model are examined to predict the thermal performance of the ground. One exactly considers the moisture movement in the ground, and the other simply takes the effect of water evaporation at the surface into consideration. In the former simulation model, called Model A, moisture in the ground moves according to the gradient of water content and thermal properties of the soil also vary according to the water content. The latter model, called Model B, uses evaporation ratio to calculate the water evaporation at the surface and thermal properties are constant. The comparison of the measured and the calculated values shows Model A is more accurate than Model B in the viewpoint of the reproducing heat transfer phenomenon on and under the ground. Model B, however, has enough accuracy to predict the heat transfer on and under the ground. Less