地源热泵埋管与土壤多年累积传热效应研究

【作者】 李大鹏；

【导师】 廖胜明；

【作者基本信息】 中南大学 ， 供热、供燃气、通风及空调工程， 2009， 硕士

【摘要】 可再生能源逐步替代常规能源是世界发展的趋势,地源热泵技术可以利用浅层地热能资源满足建筑物空调、供暖等多种需求,是运用可再生能源的重要技术手段之一,同时发展地源热泵也是确保我国能源结构调整的需要。中国国土面积巨大,土壤构造和气候差异明显,在不同地气条件下应用地源热泵的技术措施多样,因此研究不同地气条件对地源热泵系统运行性能的影响有重要的意义。本文主要采用模块化动态系统模拟软件TRNSYS对常规地源热泵系统和带辅助散热源的地源热泵系统的运行性能和土壤传热特性进行了研究。首先建立了适用于运行工况变化范围大的精确的水-水热泵模型,并验证了该模型的准确性;然后针对不同气候条件下不同建筑类型的常规地源热泵系统进行了设计模拟,结果表明在寒冷地区和夏热冬冷地区经过合理设计的地源热泵系统能够保证系统长期正常运行;在夏热冬暖地区常规地源热泵系统则很难保证系统长期正常运行。通过对比在不同设计进水温度下常规系统的总能耗发现,总能耗并不会因为降低设计进水温度而显著减少。针对冷负荷占优的建筑,对采用冷却塔为辅助散热源的混合式地源热泵系统进行了模拟分析,提出了一种以冷却塔为主的控制策略,并与已有的控制策略进行了对比分析,结果表明,对于夏热冬冷地区的混合式系统宜通过基于设定温差和温度的控制策略控制系统的运行方式;对于夏热冬暖地区的混合式系统宜通过冷却塔为主的控制策略控制系统的运行方式;冷却塔环路应该与地埋管环路并联运行,并应使通过地埋管环路的水流量与总水流量的比例与地埋管换热器所承担的释热量比例相对应。最后,对制冷、制热和制热水的多功能地源热泵系统进行模拟,结果表明,应用多功能地源热泵系统可以明显改善地下土壤全年释热量与吸热量的不平衡性;多功能地源热泵系统与传统系统相比,运行一年的系统总能耗可以节省46%。根据不同的经济性参数,生命周期内的费用现值节约率变化范围在7%～40%,投资回收期变化范围在5～12年。本文所建立的模型可以很容易的推广应用在实际工程项目中去,所得结论对地源热泵系统的合理设计与能耗预测具有重要意义。更多还原

【Abstract】 It is a trend of world development that renewable energy is gradually to replace conventional energy, and ground source heat pump (GSHP) technology, which meets buildings needs of air-conditioning, heating etc. by utilizing shallow geothermal resource, is an important means of the use of renewable energy; meanwhile, developing GSHP is also the requirement of China’s energy construction adjustment. China’s land area is huge, and soil formation and climate, as well as the technology measures of GSHP applications, varied significantly at different zones, therefore it is significant to investigate the effects of soil and climate conditions on the performance of GSHP system.In this paper, the performance of conventional GSHP and GSHP with auxiliary heat rejecter and heat transfer characteristics of the soil were studied with a transient modular system simulation software TRNSYS. Firstly, a water-water heat pump model, which can be run accurately in a wide range of operating conditions, was established, and the accuracy of the model was verified. Then conventional GSHP system in three climate zone for two different building types was designed and simulated, and the results showed GSHP with proper design in cold zone and hot summer and cold winter (HSCW) zone could ensure normal operation over an extended period, however the one in hot summer and warm winter (HSWW) zone was difficult to guarantee normal operation. The relation of the design entrance water temperature (EWT) of heat pump and total system energy consumption was investigated, and the result suggested that total energy consumption did not significantly reduce with decreasing the design EWT.The investigation of Hybrid GSHP system with cooling tower as auxiliary heat rejecter was performed in cool load dominant buildings, and a novel control strategy i.e. cooling tower priority was carried out and compared from some known control strategy. The result of analysis showed that hybrid GSHP in HSCW zone should be controlled by the strategy based on set temperature different and temperature, and the one in HSWW zone should be modulated by the novel control strategy. And the ratio of flow rate through borehole loop to total flow rate should correspond to the ratio of the load that borehole loop would release to total load.Finally, a multi-functional GSHP system with cooling, heating and domestic hot water was developed and analysed. The result of investigation showed that multi-functional system can significantly improve the thermal balance of the soil; compared with traditional system, energy consumption reduced 46 percent, and the saving of the present valve of life-cycle costs ranged from 7%-40% and investment payback period ranged from 5-12 years depended on economic analysis parameters.These models developed in this paper can be easily applied in practical projects, and the conclusion is of significance for proper design and energy consumption forecast of GSHP system.更多还原