Numerical Simulation Study On Heat Transfer Of Coil Inside Foundation Piles

This paper has built a two-dimensional unsteady numerical model of coil ground heatexchanger inside foundation piles which shows the mathematical model, geometric model,mesh generation, physical property parameter, single valued conditions and so on. And then，numerical analysis of coil ground heat exchanger inside foundation piles has been carried outwith Fluent software.Firstly, the paper compares the computed result of the two-dimensional unsteadynumerical model with the thermal response tests data, and the results indicate that they fitwith each other—the average relative error of the inner circulating water average temperatureof the coil inside piles is only0.19%. The heat exchange amount which under the heat transfertemperature difference of these two tests is1.70%. It can be seen that this model is credible.Secondly, the paper analyzes the influences of different spiral coil spacing, different pilefoundation depths and different initial soil temperature on heat transfer. The simulation resultshows the quantity of spiral coil ground heat exchanger per meter has a linear relationshipwith spiral coil spacing within the range of0.1m to0.5m. The more the spacing increasing,the more the heat gain decreasing. But with the increasing of pile foundation depths, thequantity of spiral coil ground heat exchanger only decreasing slightly, the relative decrementper meter is less than1.1%.Lastly, the annual dynamic coupling simulation of coil ground heat exchanger insidefoundation piles has been studied. And the temperature of hourly variation trend from theinlet-outlet of the ground heat exchanger is obtained by calculating. It turns out that the trendof inlet-outlet temperature variation of ground heat exchanger is same to the building dynamicload changes. The temperature difference between inlet and outlet of ground heat exchangerhas remained steady at about2℃-3℃in summer and1℃-2℃in winter. It can check thedesign of ground heat exchanger by simulating the annual inlet-outlet temperature change ofheat exchanger. And it also can provide a research foundation for the year-round operation ofcooling water heat exchanger of ground source heat pump.