| As a cold and heat source technology which is green energy, the use of renewableenergy-ground source heat pump, and in recent years has been the rapid developmentin the country. As a new type of pile spiral pipe ground source heat pump system, whichnot only has a ground source heat pump system has many advantages, but also greatlyease the high initial investment of ground source heat pump system caused by thedrilling, environmental pollution and other issues. Therefore, it is of great significanceto grasp the heat transfer performance of pile spiral pipe heat exchanger system andrefine the design of ground source heat pump system.In this paper, the theory on the pile spiral pipe heat exchanger was analyzed. Theanalytical model and numerical model were established, and the numerical modelverified and analyzed, the numerical solution in good agreement with the measuredvalues. The calculation formula of the hourly inlet and outlet water temperature of heatexchanger and stratum thermal resistance was derived.Based on the project of Xifeng County People’s Hospital pile spiral pipe groundsource heat pump system, in the region of soil thermal properties parameters on thethermal resistance were calculated, analyzed the proportion of thermal resistance andthe growth law of stratum thermal resistance with time. The experimental table wasestablished, experimental study was carried out, and the heat exchanger performanceunder different pitch was contrasted and analyzed, in the process of implementing theproject sums up the pile spiral pipe heat exchanger system construction technology. Theexperimental results showed that: the heat transfer resistance of different pitches weredifferent, the single spiral (pitch300mm) average thermal resistance than the threehelix (pitch100mm) little35.67%, than the double helix (pitch for the150mm) ofsmall9.14%, the average resistance than the three double helix spiral small26.54%;When the flow velocity in the range of0.24~0.8m/s changed, the influence of velocityon the pile spiral pipe heat exchanger was small; the pile spiral pipe heat exchangerswith different helical form of heat properties, helical, double helix and the three helixaverage heat flux of unit pipe length were respectively35.2W/m,25.5W/m and19.5W/m; System shutdown recovery, foundation pile soil temperature field around andvertical U shape buried pipe of different pile wall, the soil near the first experiencecontinues to warm up, then cooling process. For Xifeng Case, the effect of main factors upon pile spiral pipe heat exchangerwas simulated, and the result indicated that: the depth of pile foundation was notsignificant effect on heat transfer performance of the pile spiral tube heat exchanger,unit depth heat transfer at a depth of9.9m was increases by5.2W/m than that of a depthof8.4m, water temperature0.32℃; it was very small impacted that backfill original soiland backfill concrete for pile spiral pipe heat exchanger on heat transfer performance;pile spiral pipe heat exchangers heat flux of unit pipe length and water temperature asthe fluid in the pipe flow increased, its growth had been reduced; According to theresults of numerical simulation and engineering experiments and considering theoperating efficiency of the unit, the energy consumption of the system, and the pile heatexchanger temperature difference, it was recommended that the pile spiral pipe heatexchanger flow rate value did not exceed0.2m/s. |
