Numerical Simulation On Thermal Performance Of Pile Fundation Ground Heat Exchanger With Spiral Coils

As a new type heat exchanger of ground pipes,pile foundation ground heatexchanger with spiral coils system not only has many advantages of traditional groundsource heat pump system, but also greatly remits problems(such as high initialinvestment, large covers of area) caused by too many boreholes. So, it is of greatsignificance to master grasps the performance of pile foundation ground heat exchangerwith spiral coils system and the designing parameters of soil source heat pump system.So far, we are still lacking in heat transfer performance and design parameters ofpile foundation ground heat exchanger with spiral coils system. In this background, thispaper establishes a three-dimensional numerical analysis model of pile foundationground heat exchanger with spiral coils and verifies the validity of the model bycomparing the results of numerical simulation and the existing empirical method. Theinfluence of the fluid velocity, spiral tube pitch, soil thermal physical property, the inletfluid temperature, and backfill material on the performance of pile foundation groundheat exchanger with spiral coils was calculated and analyzed, and the transformationlaw of pile foundation ground heat exchanger heat exchange with spiral coils underdifferent working conditions was achieved. The results indicated that the designing flowvelocity, the screw pitch and the temperature of inlet water of pile foundation groundheat exchanger with spiral coils cannot be over high; it is known that it is of greatsignificance to popularize pile foundation ground heat exchanger with spiral coilsthrough the analyzing results of soil thermal physical properties. The numericalsimulation of the backfill material told the different influences on the performance ofpile foundation ground heat exchanger with spiral coils between different backfillmethods and different backfill materials. Through all above, the exchange performanceof pile foundation ground heat exchanger under summer working condition wasachieved.Single U and double U3D models of vertical buried tube heat exchanger wereestablished; the validity of models was verified by comparing simulated results with theresults of the thermal response test; through the methods of analyzing unit boreholedepth heat transfer performance and outlet fluid temperature. The results show theadvantages of pile foundation ground heat exchanger with spiral coils over buried tubewith boreholes. When it comes to the situation that the pile foundation ground heat exchanger with spiral coils cannot satisfy the heating/cooling load of buildings, as anew type of buried tube, the economical advantages of pile foundation ground heatexchanger were achieved through the method of making a comparison frominvestigation perspective among pile foundation ground heat exchanger with double Uburied tube.In this paper, the results indicate that pile foundation ground heat exchanger withspiral coils shows its excellence both in heat exchange performance and economicalperspective, this provides reference for its industrial application.