【作者】 王潇；

【导师】 郑茂余；

【作者基本信息】 哈尔滨工业大学 ， 供热、供燃气、通风与空调工程， 2011， 博士

【摘要】 土壤耦合热泵在严寒地区实际应用中,由于热泵从土壤中的取热量很大,系统长年运行土壤温度将逐年下降,热泵的供暖性能也将逐年降低,最终导致热泵出力不足。为此,本文基于太阳能移季利用的思想,提出将太阳能、土壤蓄热和土壤耦合热泵技术有机融合的季节性蓄热太阳能-土壤耦合热泵(SGCHPSS)系统,将非采暖季丰富的太阳能转移至冬季使用,同时解决上述问题,从而为严寒地区供暖提供新方法。为了了解该系统在严寒地区的实际应用效果和供暖性能,建立了SGCHPSS实验平台,初步给出系统的运行方式和控制方法并进行全年实验研究。通过对太阳能土壤蓄热运行特性、系统供暖运行特性和土壤全年温变特性的实测和分析得出:太阳能季节性土壤蓄热能够有效提高土壤温度,热泵的COP达到4.29,系统全年的性能系数达到6.14,冬季供热量中约87%来自于太阳能。考虑到系统的复杂性和时间的限制,对系统的进一步研究不能一一通过实验的方法实现,因此,在实验的基础上建立了该系统中各设备的数学模型,并结合实验中给定的运行方式和控制方法实现系统的动态仿真。通过将系统模拟计算结果与实验结果进行对比,验证了系统模型的正确性。为了减少计算量,忽略了土壤换热器管间的热干扰,将多管土壤换热器模型简化为单管土壤换热器模型。为了验证简化的合理性,将单管模型与多管模型进行了对比验证,结果表明:通过单管土壤换热器模型计算得到的单个钻井蓄热量和取热量与通过多管土壤换热器模型计算得到的单个钻井蓄热量和取热量的最大相对误差分别为5.9%和7.9%,均小于10%,在允许的范围内。首先,利用建立的系统数学模型对SGCHPSS系统进行变参数模拟研究,详细分析了改变系统配置参数——太阳能集热器面积、土壤换热器埋管深度和热泵制热量对系统运行特性的影响。模拟结果表明:增加集热器面积和热泵容量都有利于提高热泵和系统的供暖性能,减少运行费用,而土壤换热器埋管深度并不是越深越好,当埋管深度增加至一定程度时热泵和系统的供暖性能提升的幅度很小,同时会使运行费用增加。其次,分别对有季节性蓄热和无季节性蓄热情况下系统运行的可持续性进行了分析,得出在严寒地区长年利用土壤耦合热泵为建筑物供暖会出现热泵出力不足,耗电量不断增加,而室温却达不到要求的现象;而SGCHPSS系统可以有效提高土壤温度,使热泵的供暖性能逐年提升,系统的耗电量也逐年减少,同时可以使土壤保持以年为周期的热平衡。然后,针对实验中运行方式存在的问题,提出三种新的可行的运行方式,并与实验运行方式进行了对比分析,得出通过改变运行方式可以提升系统的供暖性能,改变系统中各设备的能量输出比例;对供暖期进行分阶段改变运行方式可以在节约电能的同时改善供暖效果。最后,给出系统可能的系统配置和运行方式,利用动态规划法对不同系统配置下的运行方式进行了优化,得出不同系统配置下的供暖期最优运行方式,再以系统费用年值为目标函数对系统配置进行了优化,从而得到在实验条件下的系统最优配置和最优运行方式。该优化方法可以为SGCHPSS系统的工程应用提供指导。通过本文的研究,证明了SGCHPSS系统具有很大的节能优势和较好的供暖性能,并为系统的优化设计和运行提供理论基础和技术支持。更多还原

【Abstract】 During the practical application of ground-coupled heat pump in severe cold area, due to the large heat extraction of the heat pump, the soil temperature would descend year by year for the system operation all the year round. As a result, the heating performance of the heat pump would drop year by year, too. Finally, the heat pump output would be insufficient. Therefore, based on the idea of transferring the solar energy between the seasons, this paper presented the solar-ground coupled heat pump system with seasonal storage (SGCHPSS), which integrated the solar energy, the soil heat storage and the ground-coupled heat pump technology organically. In this way, the abundant solar energy in the non-heating seasons was transferred to winter and the problems mentioned above could be solved. The system provides a new method for space heating in severe cold area.To find out the practical effect and heating performance of the system in severe cold area, the experimental platform of SGCHPSS system was established, the tentative operation way and control method of the system were given and the annual experiment was performed. The operating characteristics of solar soil heat storage and system heating as well as the temperature variation characteristics of the soil were tested and analysed. It can be concluded that the soil temperature could be increased effectively via solar seasonal soil heat storage, the COP of the heat pump achieved 4.29, the system annual coefficient of performance reached 6.14 and 87% of the total heat supply in winter came from the solar energy.Considering the complexity of the system and time constraints, further study of the system can not be realized though the experimental method one by one. Therefore, the mathematical model of each device in the system was established based on the experiment. Combining the operation way and control method given in the experiment, the system dynamic simulation was realized. To reduce the computional time, the thermal interference between the U-tubes of the ground heat exchanger was neglected. For verifying the rationality of the simplification, the single tube mathematical model was verified by the multi-tube mathematical model. The results show that the maximum relative errors of the heat storage capacity and heat extraction capacity of single borehole, computed separately by the single tube mathematical model and the multi-tube mathematical model, were 5.9% and 7.9%, respectively, which were all in the allowable range of less than 10%. The system mathematical models were further verified through the comparison between the simulation results and the experimental results. The system mathematical models established were first used to conduct the simulative study on varing the parameters. Impacts on system operating characteristics caused by varing the system configuration parameters including solar collector area, buried depth of ground heat exchanger and heat output of the heat pump were analyzed in detail. The simulation results show that increasing the solar collector area and the capacity of the heat pump were all favourable for improving the heating performances of the heat pump and the system as well as reducing the operating costs. However, the buried depth of the ground heat exchanger was not the deeper the better. When the buried depth increased to a certain extent, the heating performances of the heat pump and the system were enhanced little, while the operating costs would increase.Secondly, the sustainability of the system operation under the conditions of storing heat seasonally or not was analyzed respectively. The following conclusions can be drawn: in severe cold area, if the ground-coupled heat pump was used to heat the building all the year round, the heat output of the heat pump would be insufficient and the power consumption would increase continually, while the indoor temperature could not meet the requirements; the SGCHPSS could raise the soil temperature effectively, the heating performance of the heat pump was improved year by year, the power consumption of the system was also reduced year by year and the annual heat balance could be maintained in the soil. Then, in view of the existing problems of operation way in the experiment, three new and feasible operation ways were put forword and a comparative analysis with that in the experiment was conducted. It can be drawn that the heating performance of the system could be promoted and the proportion of the energy output of each device could be changed by varying the operation way; the heating effect could be improved while saving the electric energy if the heating period was divided into phases to vary the operation way.Finally, the possible system configuration and operation way were given, and the dynamic programming method was used to optimize the operation way for different system configuration. By this way, the optimal operation way for the heating period was obtained for different system configuration. Then, the annual cost was taken as the objective function to optimize the system configuration. Consequently, the optimal system configuration and operation way were gained. This optimization method can provide guidance for engineering applications of SGCHPSS system.The studies in this paper have proved that the SGCHPSS has great energy-saving advantages and better heating performance, which can provide theoretical basis and technical support for the optimization design and operation of the system.更多还原