Heat conduction performance and transfer mechanism of sand-barite powder backfill materials

Authors

JIA Hailiang, College of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, ChinaFollow
ZHU Zixian, College of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
ZHOU Yang, Shaanxi Institute of Geological Survey, Xi’an 710054, China
SUN Qiang, College of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, China

Abstract

The ground source heat pump of buried pipeline is a major form of shallow thermal energy utilization, and the thermophysical properties of backfill materials, especially the thermal conductivity, are the key factors affecting the heat transfer efficiency of the heat pump system. In this paper, the variation law of thermal conductivity of the sand-barite powder samples at different barite powder mixing ratio (volume fraction) and saturation was studied. The mechanism of improving the thermal conductivity of backfill materials with barite powder was revealed based on the macroscopic and microscopic experiments such as stereoscope and nuclear magnetic resonance analysis. In addition, the influence of the heat conduction performance of this backfill materials on heat transfer efficiency was studied by numerical simulation. The study shows that barite powder has a significant effect on the thermal conductivity of backfill materials, and the barite powder at the mixing ratio of 20% has best effect on improving the thermal conductivity of backfill materials, which could improve the thermal conductivity by 52.09% at maximum. Water content also has a significant effect on the thermal conductivity, and the thermal conductivity of the saturated sample is significantly increased, which is 4−5 times higher than that of dry sample. The improvement of the thermal conductivity of backfill materials by barite powder is mainly caused by the package and filling effect. Specifically, the package effect is to wrap the sand particles with barite powder, while the filling effect is to fill the pores between sand particles with barite powder. The numerical simulation results prove that it is feasible to improve the heat transfer efficiency of ground source heat pump by enhancing the thermal conductivity of backfill materials with barite powder. Generally, the research results provide reference for the selection of backfill materials of ground source heat pump.

Keywords

heat conduction performance，heat transfer efficiency，backfill material，barite powder，ground source heat pump，macroscopic and microscopic experiment，numerical simulation

DOI

10.12363/issn.1001-1986.22.03.0192

Recommended Citation

JIA Hailiang, ZHU Zixian, ZHOU Yang, et al. (2022) "Heat conduction performance and transfer mechanism of sand-barite powder backfill materials," Coal Geology & Exploration: Vol. 50: Iss. 11, Article 18.
DOI: 10.12363/issn.1001-1986.22.03.0192
Available at: https://cge.researchcommons.org/journal/vol50/iss11/18

Reference

[1] LUO Jin,ROHN J,BAYER M,et al. Analysis on performance of borehole heat exchanger in a layered subsurface[J]. Applied Energy,2014,123(15):55−65.

[2] 赵春虎,尚宏波,靳德武,等. 深层垂直井同轴换热能力数值模拟分析[J]. 煤田地质与勘探,2020,48(5):174−181

ZHAO Chunhu,SHANG Hongbo,JIN Dewu,et al. Numerical simulation of coaxial heat transfer capacity of deep vertical wells[J]. Coal Geology & Exploration,2020,48(5):174−181

[3] 庄迎春,谢康和,孙友宏. 砂土混合材料导热性能的试验研究[J]. 岩土力学,2005,26(2):261−264

ZHUANG Yingchun,XIE Kanghe,SUN Youhong. Experimental study on thermal conductivity of mixed materials of sand and bentonite[J]. Rock and Soil Mechanics,2005,26(2):261−264

[4] 邹行,裴鹏,郝定溢,等. 不同土壤类型与含水率对水平埋管换热性能影响数值分析[J]. 煤田地质与勘探,2021,49(6):221−229

ZOU Hang,PEI Peng,HAO Dingyi,et al. Numerical analysis of the effect of different soil types and water content on heat transfer performance of horizontal buried pipes[J]. Coal Geology & Exploration,2021,49(6):221−229

[5] YI Dong,MCCARTNEY J S,LU Ning. Critical review of thermal conductivity models for unsaturated soils[J]. Geotechnical and Geological Engineering,2015,33(2):207−221.

[6] ADUDA B O. Effective thermal conductivity of loose particulate systems[J]. Journal of Materials Science,1996,31(24):6441−6448.

[7] ESCH D C. Thermal analysis，construction，and monitoring methods for frozen ground[M]. Virginia：American Society of Civil Engineers，2004.

[8] 杨雨,徐拴海,张浩,等. 填料对地热井固井材料导热性能的影响[J]. 煤田地质与勘探,2020,48(5):182−189

YANG Yu,XU Shuanhai,ZHANG Hao,et al. Effect of thermally conductive filler on thermal conductivity of cementing materials in geothermal wells[J]. Coal Geology & Exploration,2020,48(5):182−189

[9] WAN Rong,KONG Dequan,KANG Jiayuan,et al. The experimental study on thermal conductivity of backfill material of ground source heat pump based on iron tailings[J]. Energy and Buildings,2018,174:1−12.

[10] LEE C,LEE K,CHOI H,et al. Characteristics of thermally–enhanced bentonite grouts for geothermal heat exchanger in South Korea[J]. Science in China Series E:Technological Sciences,2010,53:123−128.

[11] ALRTIMI A A,ROUAINIA M,MANNING D A C. Thermal enhancement of PFA−based grout for geothermal heat exchangers[J]. Applied Thermal Engineering,2013,54(2):559−564.

[12] DINH B H,KIM Y S,KANG G O. Thermal conductivity of steelmaking slag−based controlled low−strength materials over entire range of degree of saturation:A study for ground source heat pump systems[J]. Geothermics,2020,88:101910.

[13] WANG Huajun,CUI Yahui,QI Chengying. Effects of sand–bentonite backfill materials on the thermal performance of borehole heat exchangers[J]. Heat Transfer Engineering,2013,34(1):37−44.

[14] NOEL J A,WHITE M A. Freeze–cast form–stable phase change materials for thermal energy storage[J]. Solar Energy Materials and Solar Cells,2021,223:110956.

[15] KONG M,ALVARADO J L,THIES C,et al. Field evaluation of microencapsulated phase change material slurry in ground source heat pump systems[J]. Energy,2017,122:691−700.

[16] ZHENG Huanpei,WANG Changhong,LIU Qingming,et al. Thermal performance of copper foam/paraffin composite phase change material[J]. Energy Conversion and Management,2018,157:372−381.

[17] 雷彦鹏. 地源热泵工程固废基回填材料的研发与应用研究[D]. 济南：山东大学，2020.

LEI Yanpeng. Research on R&D and application of solid waste–based backfill materials for ground source heat pump engineering[D]. Jinan：Shandong University，2020.

[18] 姜雅,王婷. 中美贸易关系中重晶石资源作用分析[J]. 中国矿业,2021,30(9):36−41

JIANG Ya,WANG Ting. Analysis of the role of barite resources in Sino−US trade relations[J]. China Mining Magazine,2021,30(9):36−41

[19] 中华人民共和国水利部，中华人民共和国住房和城乡建设部. 土工试验方法标准：GB/T 50123—2019[S]. 北京：中国计划出版社，2019.

[20] 肖立志. 核磁共振成像测井与岩石核磁共振及其应用[M]. 北京：科学出版社，1998.

[21] 贾海梁,陈伟航,王婷,等. 微波照射冻土热融软化规律试验研究[J]. 岩石力学与工程学报,2020,39(增刊2):3636−3644

JIA Hailiang,CHEN Weihang,WANG Ting,et al. Experimental study on the thawing and softening laws of frozen soil under microwave irradiation[J]. Chinese Journal of Rock Mechanics and Engineering,2020,39(Sup.2):3636−3644

[22] JIA Hailiang,DING Shun,WANG Yan,et al. An NMR–based investigation of pore water freezing process in sandstone[J]. Cold Regions Science and Technology,2019,168:102893.

[23] KLEINBERG R L,KENYON W E,MITRA P P. Mechanism of NMR relaxation of fluids in rock[J]. Journal of Magnetic Resonance,1994,108(2):206−214.

[24] 李杰林. 基于核磁共振技术的寒区岩石冻融损伤机理试验研究[D]. 长沙：中南大学，2012.

LI Jielin. Experimental study on deterioration mechanism of rock under the conditions of freezing–thawing cycles in cold regions based on NMR technology[D]. Changsha：Central South University，2012.

[25] 王福军. 计算流体动力学分析：CFD软件原理与应用[M]. 北京：清华大学出版社，2004.

[26] 黄雪婷. 竖直U型地埋管换热性能主要影响因素数值研究[D]. 西安：长安大学，2014.

HUANG Xueting. Numerical study on the main influencing factors of U−shaped vertical ground heat exchanger performance[D]. Xi’an：Chang’an University，2014.

[27] 王硕,殷元生,黄可钦,等. 同轴套管深埋管换热器延米换热量变化规律的研究[J]. 工业加热,2019,48(2):5−9

WANG Shuo,YIN Yuansheng,HUANG Keqin,et al. Research on the change of heat transfer rate per meter in deep coaxial borehole heat exchanger[J]. Industrial Heating,2019,48(2):5−9

[28] MURAYA N K,ONEAL D L,HEFFINGTON W M. Thermal interference of adjacent legs in a vertical U−tube heat exchanger for a ground−coupled heat pump[J]. ASHRAE Transactions,1996,102(2):12−21.