U型中深层地埋管换热器(U-bend Deep Borehole Heat Exchanger,UDBHE)可有效开采中深层地热能,具有较高的换热性能,因而备受关注。中深层岩土热物性一般随深度而变化,而目前缺乏分层岩土热物性对U型中深层地埋管换热器传热性能影响的深...U型中深层地埋管换热器(U-bend Deep Borehole Heat Exchanger,UDBHE)可有效开采中深层地热能,具有较高的换热性能,因而备受关注。中深层岩土热物性一般随深度而变化,而目前缺乏分层岩土热物性对U型中深层地埋管换热器传热性能影响的深入研究。文章基于已经建立的UDBHE半解析传热模型,研究了分层岩土热物性(热导率和体积比热容)对UDBHE传热性能的影响。研究结果表明:各层岩土热导率和体积比热容对UDBHE传热性能均有一定影响,并且其影响均随着岩土层深度的增大而增大;随着时间的增加,岩土热导率造成的影响逐渐增大,而岩土体积比热容造成的影响基本不变。保持各层岩土热导率的加权平均值不变,岩土热导率非均匀性对传热性能有较大影响,并且较大的岩土热导率非均匀性程度将促进UDBHE传热性能,反之则抑制。同理,岩土体积比热容非均匀性也有一定影响,但其影响随时间变化很小。研究结果对UDBHE性能预测及优化提供重要的参考价值。展开更多
In this research,the thermal performance of a single U-tube vertical ground heat exchanger is evaluated numerically as a function of the most influential flow parameters,namely,the soil porosity,volumetric heat capaci...In this research,the thermal performance of a single U-tube vertical ground heat exchanger is evaluated numerically as a function of the most influential flow parameters,namely,the soil porosity,volumetric heat capacity,and thermal conductivity of the backfill material,inlet volume flow rate,and inlet fluid temperature.The results are discussed in terms of the variations of the heat exchange rate,the effective thermal resistance,and the effectiveness of the ground heat exchanger.They show that the inlet volume flow rate,inlet fluid temperature,and backfill material thermal conductivity have significant effects on the thermal performance of the ground heat exchanger,such that by decreasing the inlet volume flow rate and increasing the backfill material thermal conductivity and inlet fluid temperature,the outlet fluid temperature decreases considerably.On the contrary,the soil porosity and backfill material volumetric heat capacity have negligible effects on the studied ground heat exchanger’s thermal performance.The lowest inlet fluid temperature reaches a the maximum effective thermal resistance of borehole and soil,and consequently the minimum heat transfer rate and effectiveness.Also,multilinear regression analyses are performed to determine the most feasible models able to predict the thermal properties of the single U-tube ground heat exchanger.展开更多
文摘U型中深层地埋管换热器(U-bend Deep Borehole Heat Exchanger,UDBHE)可有效开采中深层地热能,具有较高的换热性能,因而备受关注。中深层岩土热物性一般随深度而变化,而目前缺乏分层岩土热物性对U型中深层地埋管换热器传热性能影响的深入研究。文章基于已经建立的UDBHE半解析传热模型,研究了分层岩土热物性(热导率和体积比热容)对UDBHE传热性能的影响。研究结果表明:各层岩土热导率和体积比热容对UDBHE传热性能均有一定影响,并且其影响均随着岩土层深度的增大而增大;随着时间的增加,岩土热导率造成的影响逐渐增大,而岩土体积比热容造成的影响基本不变。保持各层岩土热导率的加权平均值不变,岩土热导率非均匀性对传热性能有较大影响,并且较大的岩土热导率非均匀性程度将促进UDBHE传热性能,反之则抑制。同理,岩土体积比热容非均匀性也有一定影响,但其影响随时间变化很小。研究结果对UDBHE性能预测及优化提供重要的参考价值。
文摘In this research,the thermal performance of a single U-tube vertical ground heat exchanger is evaluated numerically as a function of the most influential flow parameters,namely,the soil porosity,volumetric heat capacity,and thermal conductivity of the backfill material,inlet volume flow rate,and inlet fluid temperature.The results are discussed in terms of the variations of the heat exchange rate,the effective thermal resistance,and the effectiveness of the ground heat exchanger.They show that the inlet volume flow rate,inlet fluid temperature,and backfill material thermal conductivity have significant effects on the thermal performance of the ground heat exchanger,such that by decreasing the inlet volume flow rate and increasing the backfill material thermal conductivity and inlet fluid temperature,the outlet fluid temperature decreases considerably.On the contrary,the soil porosity and backfill material volumetric heat capacity have negligible effects on the studied ground heat exchanger’s thermal performance.The lowest inlet fluid temperature reaches a the maximum effective thermal resistance of borehole and soil,and consequently the minimum heat transfer rate and effectiveness.Also,multilinear regression analyses are performed to determine the most feasible models able to predict the thermal properties of the single U-tube ground heat exchanger.
