并联双U型桩基埋管换热器换热性能研究

本文建立了并联双U型桩基埋管换热器传热问题的三维数学模型,利用江苏某工程现场实测数据验证了所建立模型数值解的准确性。对不同循环液流速,不同桩基长度和不同运停比等工况下埋管出口水温,单位桩深换热量,桩周温度以及桩周土壤温度进行了分析,揭示了出口水温、单位桩深换热量等性能参数在不同工况下的动态变化规律以及桩身和周围土壤温度改变而产生的热堆积现象,提出了单位桩身温度变化换热量β1和单位土壤温度变化换热量β2,评价了不同工况对换热性能影响程度。结果表明,高流速可以增强换热,但高流速工况下为了产生更多的换热量而带来的代价是更高的桩身和土壤温升,不利于长期运行。长桩基长度工况和运停工况可以在有利于长期运行前提下提高埋管换热器的换热量,且运停工况对换热性能的提升更为明显。

Study on Heat Transfer Performance of Parallel Double U-type Pile Foundation Tube Heat Exchanger

The three-dimensional model of the parallel double U-shaped pile foundation tube heat exchanger is established,and the measured value of a project site in Jiangsu is used as the comparison to verify the accuracy of the established model.The water temperature at the outlet of the buried pipe,the heat exchange capacity per unit pile,the temperature around the pile,and the soil temperature around the pile were carried out under the conditions of different circulating fluid flow rates,different pile foundation lengths,and different operation and stop ratios.The analysis reveals the dynamic change law of the performance parameters such as the outlet water temperature and the heat exchange capacity per unit pile under different working conditions and the heat accumulation phenomenon caused by the change of the soil temperature of the pile body and the surrounding soil.The heat exchange capacity β1 and the unit soil temperature β2 was evaluated,and the influence degree of different working conditions on heat transfer performance was evaluated.The results show that high flow rate can enhance heat transfer,but the cost of generating more heat transfer under high flow conditions is higher pile body and soil temperature rise,which is not conducive to long-term operation;long pile long working condition And the operation and stop working conditions can improve the heat exchange capacity of the buried heat exchanger under the premise of facilitating long-term operation,and the improvement of heat transfer performance is more obvious in the operation and stop working conditions.