含重晶石粉回填料提升地埋管换热能力研究

Heat transfer capacity analysis of buried pipe borehole with barite powder backfill

为研究含重晶石粉回填料对平原区第四系和山区岩石地层钻孔地埋管换热能力的影响,开展了导热系数测试实验比对分析、现场热响应实验和长期运行条件的模拟计算。平原区第四系钻孔采用中砂回填,山区基岩钻孔采用水泥砂浆回填。室内导热系数测试发现:中砂回填料中重晶石粉质量分数为5%时,导热系数提升14.3%;水泥砂浆中添加5%的重晶石粉,导热系数提升7.3%。钻孔现场热响应测试发现:同一场地内夏季工况下,平原区含5%重晶石粉回填料钻孔地埋管延米换热量提高2.4 W/m,换热效率提升3.5%;山区内含5%重晶石粉水泥砂浆回填料钻孔地埋管延米换热量提高2.7 W/m,换热效率提升3.9%。经数值模拟计算,钻孔回填料重晶石粉质量分数提升至10%,地埋管延米换热能力提高约6.0%。总体上添加重晶石粉后地埋管换热能力得到提高且可持续性较好。

In order to study the effect of backpacking containing barite powder on the heat transfer efficiency of buried pipe boreholes in plain and mountainous areas of Beijing,a comparative analysis of laboratory experiments and field thermal response experiments was carried out.The quaternary boreholes in plain areas were backfilled with medium sand and the bedrock boreholes in mountainous areas were backfilled with cement mortar.When the specific gravity of medium sand barite powder was 5%,the thermal conductivity of medium sand backfill samples increased by 14%.When 5%barite powder was added to cement mortar,the thermal conductivity increased 7.3%.According to the field thermal response test results,under summer conditions in the same site,the heat transfer rate of a backfilling borehole containing barite powder increased by 2.4 W/m and 3.5%per meter compared with that of the medium-sand backfilling borehole in plain area.The heat transfer rate of cement mortar backfill containing barite powder increased by 2.7 W/m and 3.9%per meter.The numerical simulation model of the quaternary system and bedrock area was established.It was found that the content of barite powder increased to 10%and the heat transfer rate of boreholes increased by about 6.0%.In general,the heat transfer capacity of buried pipe is improved and its sustainability gets better after adding barite powder.