摘要
以地源热泵技术在寒区设施农业中的应用为背景,开展地下换热器低温冻胀特性研究。通过岩土埋管冻胀试验,基于冻结半径追踪和管体应变测量,开展冻结区发展规律以及埋管变形收缩特性的研究,对比砂土基和黏土基回填料对冻胀的影响,并进一步考察换热管容积与流阻变化。结果表明,冻结区在进出水2管中心连线方向发展速度大于其垂直方向,受冻胀影响,U型换热管产生椭圆化变形与收缩,砂土基回填比黏土基回填具有更大的冻结范围,但前者换热管变形和收缩程度却小于后者。换热管在100 h内持续由0降至-10℃后,测得管容积减小率为0.4%,流阻增大率为6.5%,由此可知,埋管冻胀的变形与收缩成为循环流量减小和系统效率下降的原因之一。
Based on the ground source heat pump technology(GSHP)application in facility agriculture in cold regions,the frost heave characteristics of ground heat exchanger were studied.The research,based on the freezing radius tracking and pipe surface strains measurement,was carried out by frost heave experimental system.The experimental system mainly included soil tank,surrounding soil(ground soil and backfill material),U-type heat exchange pipe and cold source circulation system.In order to reflect better the effects of soil frost heave on pipe,uniform and saturated surrounding soil was used,the initial temperature of which was 4℃.The effects of sand-based and clay-based backfill materials on frost heave were contrasted.The frost-susceptible natural clay was applied as ground soil and clay-based backfill material,the mixture of fine sand and bentonite was applied as sand-based backfill material.In the experiment,the cryogenic fluid circulated in the U-pipe for 100 hours continuously,the temperature of which reduced from 0 to-10℃.The research on the characteristics of freezing area growth,buried pipe deformation and contraction were developed.Moreover,the changes of heat exchange pipe volume and flow resistance due to pipe deformation were investigated.In this study,the X direction was defined as the line through two centers of inlet pipe and outlet pipe,the Y direction was perpendicular to X direction.It could be found in both backfill materials,the running time in the X direction was less than the Y direction at the corresponding freezing radius.This was related to the structure of U-pipe with two side-by-side pipes.The difference decreased with the increase of freezing area.In contrast,the freezing radius growth rate in the sand-based backfill(the rates in X and Y direction were 1.64 and 1.43 mm/h respectively)was slightly larger than that of the clay-based backfill(the rates in X and Y direction were 1.58 and 1.37 mm/h respectively).This indicated the freezing area in the sand-based backfill was greater than that
作者
王有镗
郑斌
王春光
李成宇
毛明明
刘旭阳
Wang Youtang;Zheng Bin;Wang Chunguang;Li Chengyu;Mao Mingming;Liu Xuyang(School of Transportation and Vehicle Engineering,Shandong University of Technology,Zibo 255049,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2019年第14期205-211,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金资助项目(51806130)
山东省自然科学基金资助项目(ZR2017LEE031)
山东省重点研发计划资助项目(2019GHY112076)
关键词
热泵
传热
冻胀
地下换热器
回填料
埋管变形
heat pumps
heat transfer
frost heave
ground heat exchanger
backfill material
buried pipe deformation
