基于显热容法的地源热泵地埋管换热器周围土壤冻结特性研究
Study on freezing characteristics of soil around ground heat exchangers of ground-source heat pumps based on apparent heat capacity method
摘要：
为了探讨寒冷地区土壤冻结对地源热泵地埋管换热器换热特性的影响，建立了考虑土壤冻结的地埋管周围土壤传热模型，并利用显热容法对冻结相变问题进行了处理。基于模型的数值求解探讨了土壤含水率、原始温度、热扩散率及Stefan数对埋管周围土壤温度分布及冻结速度的影响。结果显示，与未考虑土壤冻结相比，计算出的地埋管周围土壤温度高，传热热阻小，从而可以减小埋管的设计长度，降低系统初投资；提高土壤含水率有利于地源热泵的设计与运行；减小热扩散率和Stefan数可以有效地降低土壤的冻结速度。
Abstract：
In order to search the effect of soil freezing on heat exchange characteristics of ground heat exchangers in cold zone, develops a heat transfer model of soil around ground heat exchangers taking soil freezing into consideration, and solves the freezing phase change problem by apparent heat capacity method. Based on the numerical solution of the model, discusses the influences of the water content in soil, soil initial temperature, soil thermal diffusivity and Stefan number on soil temperature distribution and freezing velocity. The results indicate that the soil temperature is higher compared with unfreezing conditions and thus the heat transfer resistance is smaller, which contributes to the decrease of design length of the buried coil and system initial cost. It also proves that the increase of water content in soil is favorable to the design and operation of ground-source heat pumps. Moreover, the decrease of soil thermal diffusivity and Stefan number can stay effectively the soil freezing velocity.
Keywords:ground-sourceheatpump,groundheatexchanger,soilfreezing,apparentheatcapacitymethod