地源热泵回填材料优化集成及导热特性研究

发布时间：2018-11-17 12:33

【摘要】：地源热泵是利用浅层地热能对建筑物进行供暖制冷的高效节能环保型空调,其中垂直土壤埋管系统由于节约用地、换热性能好、不消耗地下水,在我国得到了最广泛的应用。地源热泵的利用成为了应对全球能源危机、气候变暖、发展低碳经济的重要途径。垂直土壤埋管地源热泵机组设计的关键技术是地下土壤热交换器,而地下土壤中的热量是经换热孔中的回填材料传递给U形管及管内液体的。高导热性能的回填材料可以降低换热孔内的热阻,减少地下换热孔深度和换热管长度,从而减少地源热泵的安装成本,推广使用地源热泵。本文在兼顾地源热泵回填材料传热特性、工程性能和造价、稳定环保的基础上,对膨润土基和水泥基两种回填材料进行了配比测试和优化集成,取得了以下成果:(1)膨润土基回填材料导热系数受骨料含量、干密度、含水率、孔隙率的影响规律。(2)水泥基回填材料的最优水灰比为0.55,最佳砂灰比2.0;内掺3%的天然石墨粉,导热系数增大17.8%;内掺8%的缓凝泵送型混凝土膨胀剂,可以显著提高膨胀特性,并且产生11%的减水作用,导热系数也有所增大。(3)膨润土基和水泥基回填材料的导热系数都随温度升高而增大,地温梯度变化有助于提高回填材料的导热能力。(4)添加聚丙烯类阻裂纤维,能显著提高回填材料抗裂性,抑制干湿循环裂隙。(5)优化集成后得出了两种回填材料的适宜配比,具有良好的导热能力和工程性能,能够明显降低换热孔深度和换热管长度,减少工程造价。
[Abstract]:Ground-source heat pump (GSHP) is an efficient energy-saving and environment-friendly air conditioning system which uses shallow geothermal energy to heat and refrigeration buildings. The vertical soil buried pipe system is widely used in our country because of saving land, good heat transfer performance and no consumption of groundwater. The utilization of ground source heat pump has become an important way to deal with the global energy crisis, climate warming and the development of low carbon economy. The key technology of the design of vertical buried pipe ground source heat pump unit is the underground soil heat exchanger, and the heat in the underground soil is transferred to the U-tube and the liquid in the pipe through the backfill material in the heat exchange hole. The backfill material with high thermal conductivity can reduce the heat resistance in the heat exchange hole, reduce the depth of the underground heat transfer hole and the length of the heat exchanger pipe, thus reduce the installation cost of the ground source heat pump and popularize the use of the ground source heat pump. On the basis of considering heat transfer characteristics, engineering performance and cost of backfill materials of ground-source heat pump, and stabilizing environmental protection, the ratio test and optimization integration of bentonite based backfill materials and cement based backfill materials are carried out in this paper. The results are as follows: (1) the thermal conductivity of bentonite based backfill is affected by aggregate content, dry density, moisture content and porosity. (2) the optimum water-cement ratio of cement-based backfill is 0.55 and the optimum sand / cement ratio is 2.0; When 3% of natural graphite powder is added, the thermal conductivity increases by 17.8%. Adding 8% retarding and pumping type concrete expansion agent can significantly improve the expansion characteristics and produce 11% water reducing effect. (3) the thermal conductivity of bentonite and cement based backfill materials increases with the increase of temperature, and the change of geothermal gradient is helpful to improve the thermal conductivity of backfill materials. It can obviously improve the crack resistance of backfill material and restrain dry-wet cycle crack. (5) the optimum ratio of two backfill materials is obtained after optimization and integration, which has good thermal conductivity and engineering performance. It can obviously reduce the depth of heat transfer hole and the length of heat transfer pipe, and reduce the engineering cost.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU83;P314

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