中深层套管式地埋管地源热泵系统能效分析
Energy efficiency analysis for medium-deep coaxial borehole ground-source heat pump systems
摘要：
中深层套管式地埋管地源热泵系统的能效受多种因素影响,为保证其高效运行,对其影响因素进行研究尤为重要。本文建立了中深层套管式地埋管地源热泵系统换热器传热模型,采用工程实测数据验证该模型的准确性。基于该模型,量化了一个供暖期内多种因素对系统能效的影响。结果表明:进口水温和岩土导热系数对系统能效具有重要影响,回填材料导热系数对其影响较小;增大循环流量会提高取热功率,但系统能效也随之降低,当循环流量由8.33 kg/s增大至10.56 kg/s时,取热功率提升4.95%,能效下降1.23%;增大外管管径、岩土和回填材料的导热系数能够提升系统能效,但达到一定数值后,对能效提升效果不显著。本研究对中深层套管式地埋管地源热泵系统长期稳定运行及能效提升具有参考意义。
Abstract：
The energy efficiency of the medium-deep coaxial borehole ground-source heat pump systems (MDGSHPs) is affected by multiple factors, and to ensure their efficient operation, it is particularly important to study their influencing factors. In this paper, a heat transfer model of MDGSHPs’ heat exchanger is established, and the accuracy of the model is verified by engineering-measured data. The influence of multiple factors on the energy efficiency of the system is quantified based on this model during one heating period. The results show that the inlet water temperature and the thermal conductivity of rock soil have an important impact on the energy efficiency of the system, while the thermal conductivity of the backfill material has little influence on it. Increasing the circulation flow rate will improve the heat extraction rate, but the energy efficiency of the system will decrease. When the circulation flow rate increases from 8.33 kg/s to 10.56 kg/s, the heat extraction rate increases by 4.95%, and the energy efficiency decreases by 1.23%. Increasing the outer pipe diameter and the thermal conductivity of rock soil and backfill material can improve the energy efficiency of the system, while it is not obvious to improve the energy efficiency after reaching a certain value. This study has reference significance for the long-term stable operation and energy efficiency improvement of MDGSHPs.
Keywords:medium-deep geothermal energy; ground-source heat pump; coaxial borehole heat exchanger; operation performance; energy efficiency analysis