Optimization of parameters for backfill heat exchanger in deep mines

IF 3.5 2区工程技术 Q3 ENERGY & FUELS Geothermics Pub Date : 2024-07-04 DOI:10.1016/j.geothermics.2024.103091

Ya Yin , Lan Qiao , Qingwen Li , Lu Chen

{"title":"Optimization of parameters for backfill heat exchanger in deep mines","authors":"Ya Yin , Lan Qiao , Qingwen Li , Lu Chen","doi":"10.1016/j.geothermics.2024.103091","DOIUrl":null,"url":null,"abstract":"<div>Based on the current status of laying buried pipes in the backfill to extract geothermal at home and abroad, a three-dimensional non-steady-state Mineral-geothermal co-mining model was established using COMSOL software. Firstly, under the same geometric and physical conditions, the performance of S-S, T-S and l-S Backfill Heat Exchanger (BFHE) were compared and analyzed. The results showed that the comprehensive evaluation index of the S-S BFHE was better than that of T-S and l-S BFHE. Secondly, the influence of pipe diameter <math><msub><mi>d</mi><mi>p</mi></msub></math>, inlet temperature <math><msub><mi>T</mi><mrow><mi>i</mi><mi>n</mi></mrow></msub></math> and flow velocity <math><msub><mi>u</mi><mi>f</mi></msub></math> of circulating medium, thermal conductivity <math><msub><mi>λ</mi><mi>b</mi></msub></math>and specific heat capacity <math><msub><mi>C</mi><msub><mi>P</mi><mi>b</mi></msub></msub></math>of the backfill on the coupled heat pump characteristics were studied. It was found that increasing the <math><msub><mi>d</mi><mi>p</mi></msub></math> can increase the heat transfer efficiency, but the improvement in heat transfer performance is not significant when it reaches a certain size. Low <math><msub><mi>T</mi><mrow><mi>i</mi><mi>n</mi></mrow></msub></math> can achieve higher heat exchange efficiency. Increasing the <math><msub><mi>u</mi><mi>f</mi></msub></math> can effectively improve heat transfer efficiency, but it is also limited. Considering the heat transfer efficiency, <math><msub><mi>d</mi><mi>p</mi></msub></math>, <math><msub><mi>T</mi><mrow><mi>i</mi><mi>n</mi></mrow></msub></math>, and <math><msub><mi>u</mi><mi>f</mi></msub></math> are recommended to be around 30–35 mm, 10–12℃, and 0.4–0.6 m/s respectively. The high <math><msub><mi>λ</mi><mi>b</mi></msub></math> and <math><msub><mi>C</mi><msub><mi>P</mi><mi>b</mi></msub></msub></math> can effectively increase the heat transfer performance of BFHE. Based on this, the relative sensitivity parameter was introduced to discuss the sensitivity of different influencing factors to the total heat transfer <math><msub><mi>Q</mi><mrow><mi>B</mi><mi>F</mi><mi>H</mi><mi>E</mi></mrow></msub></math>. The results showed that only the <math><msub><mi>T</mi><mrow><mi>i</mi><mi>n</mi></mrow></msub></math> had a negative impact on the <math><msub><mi>Q</mi><mrow><mi>B</mi><mi>F</mi><mi>H</mi><mi>E</mi></mrow></msub></math>. The influence of <math><msub><mi>λ</mi><mi>b</mi></msub></math>, <math><msub><mi>d</mi><mi>p</mi></msub></math>, and <math><msub><mi>u</mi><mi>f</mi></msub></math> on <math><msub><mi>Q</mi><mrow><mi>B</mi><mi>F</mi><mi>H</mi><mi>E</mi></mrow></msub></math> gradually weakened with heat transfer time, while the influence of <math><msub><mi>C</mi><msub><mi>P</mi><mi>b</mi></msub></msub></math> gradually increased. Over extended periods of operation, the thermal parameters of the backfill exert the greatest influence on the heat transfer performance of BFHEs, with thermal conductivity having the most significant effect, followed by specific heat capacity.</div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":null,"pages":null},"PeriodicalIF":3.5000,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geothermics","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0375650524001792","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENERGY & FUELS","Score":null,"Total":0}

引用次数: 0

Abstract

Based on the current status of laying buried pipes in the backfill to extract geothermal at home and abroad, a three-dimensional non-steady-state Mineral-geothermal co-mining model was established using COMSOL software. Firstly, under the same geometric and physical conditions, the performance of S-S, T-S and l-S Backfill Heat Exchanger (BFHE) were compared and analyzed. The results showed that the comprehensive evaluation index of the S-S BFHE was better than that of T-S and l-S BFHE. Secondly, the influence of pipe diameter $d_{p}$ , inlet temperature $T_{i n}$ and flow velocity $u_{f}$ of circulating medium, thermal conductivity $λ_{b}$ and specific heat capacity $C_{P_{b}}$ of the backfill on the coupled heat pump characteristics were studied. It was found that increasing the $d_{p}$ can increase the heat transfer efficiency, but the improvement in heat transfer performance is not significant when it reaches a certain size. Low $T_{i n}$ can achieve higher heat exchange efficiency. Increasing the $u_{f}$ can effectively improve heat transfer efficiency, but it is also limited. Considering the heat transfer efficiency, $d_{p}$ , $T_{i n}$ , and $u_{f}$ are recommended to be around 30–35 mm, 10–12℃, and 0.4–0.6 m/s respectively. The high $λ_{b}$ and $C_{P_{b}}$ can effectively increase the heat transfer performance of BFHE. Based on this, the relative sensitivity parameter was introduced to discuss the sensitivity of different influencing factors to the total heat transfer $Q_{B F H E}$ . The results showed that only the $T_{i n}$ had a negative impact on the $Q_{B F H E}$ . The influence of $λ_{b}$ , $d_{p}$ , and $u_{f}$ on $Q_{B F H E}$ gradually weakened with heat transfer time, while the influence of $C_{P_{b}}$ gradually increased. Over extended periods of operation, the thermal parameters of the backfill exert the greatest influence on the heat transfer performance of BFHEs, with thermal conductivity having the most significant effect, followed by specific heat capacity.

查看原文

微信好友朋友圈 QQ好友复制链接

本刊更多论文

深部矿井回填热交换器的参数优化

根据国内外在回填土中铺设埋管开采地热的现状，利用 COMSOL 软件建立了三维非稳态矿热共采模型。首先，在相同的几何物理条件下，对比分析了 S-S、T-S 和 l-S 三种回填换热器的性能。结果表明，S-S 型回填式换热器的综合评价指标优于 T-S 型和 l-S 型回填式换热器。其次，研究了管道直径 dp、循环介质的入口温度 Tin 和流速 uf、回填土的导热系数 λ 和比热容 CPbo 对耦合热泵特性的影响。研究发现，增大 dp 可以提高换热效率，但当 dp 达到一定大小时，换热性能的改善并不明显。低锡可以获得更高的热交换效率。提高 uf 可以有效提高传热效率，但也有局限性。考虑到传热效率，建议 dp、Tin 和 uf 分别为 30-35 mm、10-12℃ 和 0.4-0.6 m/s。高 λb 和 CPb 可以有效提高 BFHE 的传热性能。在此基础上，引入相对灵敏度参数来讨论不同影响因素对 QBFHE 总传热的灵敏度。结果表明，只有锡对 QBFHE 有负面影响。随着传热时间的延长，λb、dp 和 uf 对 QBFHE 的影响逐渐减弱，而 CPb 的影响逐渐增大。在长期运行过程中，回填土的热参数对 BFHE 的传热性能影响最大，其中热导率的影响最大，其次是比热容。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文去求助

来源期刊

Geothermics 工程技术-地球科学综合

CiteScore

7.70

自引率

15.40%

发文量

237

审稿时长

4.5 months

期刊介绍： Geothermics is an international journal devoted to the research and development of geothermal energy. The International Board of Editors of Geothermics, which comprises specialists in the various aspects of geothermal resources, exploration and development, guarantees the balanced, comprehensive view of scientific and technological developments in this promising energy field. It promulgates the state of the art and science of geothermal energy, its exploration and exploitation through a regular exchange of information from all parts of the world. The journal publishes articles dealing with the theory, exploration techniques and all aspects of the utilization of geothermal resources. Geothermics serves as the scientific house, or exchange medium, through which the growing community of geothermal specialists can provide and receive information.