桩芯介质对管式能量桩换热效率的影响

Influence of Pile Core Medium on Heat Transfer Efficiency of Tubular Energy Pile

管桩在中国大部分地区已经取得了较多的应用,现阶段能量桩的发展已不再局限于传统桩基础中,管桩桩基中能量桩技术也逐渐得到应用。管桩式能量桩的传热模式有别于传统能量桩,可利用其内壁空腔,提高换热效率,不同桩芯介质条件下,管桩式能量桩的换热效率有较为显著的区别。采用室内模型试验和数值模拟的方法,测得不同桩芯介质情况下管式能量桩及其桩周土体温度场的变化规律,通过控制循环导管内导热液体的流速改变能量桩的循环模式,续而探讨分析不同桩芯介质及循环流速下管式能量桩在实际运行过程中的换热效率。研究结果表明:试验条件下,桩芯介质为水的管式能量桩换热效率要高于桩芯介质为干砂的管式能量桩,且其在循环稳定时的桩身温度变化值和桩周土体的温度变化值也高于桩芯介质为干砂的情况,表明不同桩芯介质对管式能量桩的桩土温度场有显著影响,进一步验证了可通过改变管式能量桩内壁空腔的介质来提高其换热效率的可行性;同时,结合数值模拟结果发现流速的增大可以提高能量桩的换热效率,但是影响较小,而提高能量桩运行时的流速需要耗费额外的能源,表明在实际工程应用中通过提高流速的方法增加能量桩的换热效率具有较低的经济性,实际运行中的能量桩其流速满足建筑制冷供暖需求即可。

In the past decades, tubular piles have been used in most regions in China. However, presently, the energy pile, which overcomes the limitations of traditional piles, is being used widely. Tubular energy piles have gradually been developed. The heat exchange model of a tubular energy pile is different from the traditional energy pile, and the cavity of a tubular pile could be used to improve the heat exchange efficiency. The heat exchange efficiency varies under different conditions of inner media. Based on model tests and numerical simulations, the temperatures of a tubular energy pile and the surrounding soil were measured to study the heat exchange rate of tubular energy piles with different inner media. The velocity of cyclic water was controlled to study the effect of the working model on the heat exchange rate. The results show that the heat exchange efficiency with water as the inner medium is higher than that with sandy soil as the inner medium;further, the stable temperatures of the pile and surrounding soil with water as the inner medium are higher than those in the other case. This shows that the inner medium considerably influences the temperature field of tubular energy piles. Further, it is feasible to improve the heat exchange rate of energy piles by changing the inner medium. Simultaneously, the analysis of the results of numerical simulations shows that the velocity has a positive effect on the heat exchange rate;however, this effect is not pronounced. Moreover, a considerable amount of energy is required to improve the velocity of the cyclic water during the processing of energy piles, and thus, the velocity of cyclic water has lower economic benefits in improving the heat exchange rate of energy piles.