直埋闭式地源热泵回填土性能研究

回填土的性能对直埋式地源热泵的设计有一定的影响．对直埋闭式地源热泵用回填土的性能参数中的密度、含水率、饱和度以及导热系数进行了数学定义，并指出影响导热系数的主要因素是密度和含水率。用平板探针原理的室内试验的方法研究了各种物质组成情况、时间以及不同温度对导热系数的影响，并对试验的结果进行了详细的分析，得出了随各种影响因素而变化的曲线。试验结果表明，膨润土不适合单独用于回填材料，需与水泥配合并推荐使用非饱和态。导热系数随水灰比的减小而增加。掺人大颗粒的骨料是提高导热系数的有效途径，砂含量的增加使导热系数往往呈线性增长。当水灰比为0．45且砂的置换率为80％时回填材料具有较满意的导热性能，值得推荐使用。

STUDY ON PERFORMANCE OF BACKFILLED SOIL FOR VERTICAL-BURIED CLOSED-LOOP GSHP

Design and performance of ground source heat pump are depended on the thermal conductivity of the backfilled material. Mathematic definitions of parameters, such as density, water content and saturation, etc., describing the performance of backfilled material used for vertical-buried and closed-loop Ground Source Heat Pump(GSHP) were given, and that the main factors affecting thermal conductivity of backfilled material were density and water content. Laboratory tests based on the principle of flat probe for the measurement of thermal conductivity changing with materials selection and mix design, maintaining time and temperature were undertaken, and the results were analyzed in detail and prepared into some curves. It has been shown that bentonite is not suitable for backfilled material lonely, and should be mixed with cement in unsaturated state. The thermal conductivity increases with decreasing water/cement ratio. It is an effective method for increasing the thermal conductivity by adding granular fillers. An increase in sand content will increase the thermal conductivity linearly. As water/cement ratio is 0.45 and ratio of sand replacement is 80%, the backfilled material has satisfactory thermal conductivity, and is thus recommended in practical engineering of GSHP.