基于最小熵产的地埋管换热器优化设计研究

OPTIMAL DESIGN STUDY OF GROUND HEAT EXCHANGER BASED ON MINIMUM ENTROPY GENERATION

对于地埋管换热器,综合考虑传热性能和消耗的功率,建立管内流体的熵产模型。考虑两支管间热短路影响,确定流体沿管长的温度分布。以最小熵产为目标,根据沿埋管深度的温度分布,在不同换热负荷条件下,确定地埋管换热器的最优长度和管径随流量的变化关系,换热负荷确定时,埋管的最优管长随流量增加而减小,地埋管的最优管径随流量的增加而增大。在流量一定的条件下,埋管的最优管长随换热负荷的增加而增加,最优管径随换热负荷的增加也相应增大。以青岛市某实验室土壤源热泵系统为例,分析最优长度和管径对换热效能及系统性能的影响。

To improve ground heat exchanger the performance of ground source heat pump system, the entropy generation for work medium of was established considering the heat transfer performance and consumption of power. Considering the variation of fluid temperature along the length and the heat shortcircuit between adjacent legs, the fluid temperature distribution along the tube length was achieved. Optimum length and diameter for the heat exchanger is determined for different mass flows by using the second law of thermodynamics, namely the minimum entropy production. Optimum U-tube length decreases when the mass flow increases or when the heating load increases. The optimum U-tube diameter increases when the mass flow increases. The optimum length and diameter minimize entropy generation and therefore result in increased efficiency of the heat pump, provides the optimal methods and it gives references for plan optimization evaluation of the ground source heat pump system.