The prediction of borehole thermal performance is crucial in the performance evaluation and cost-effective use of a ground source heat pump (GSHP). As a result, before adapting to the thermal design of the ground heat exchangers, it is necessary to examine these correlations and expose their accuracy limits. The purpose of this paper is to assess the available borehole thermal resistance predictions in the direct ground exchange (DX) condenser when it circulates R-410A refrigerant. To forecast the thermal resistance of vertical single and double U-tube heat exchangers for various geometric configurations, eleven selected correlations in the open literature were analysed. The borehole thermal resistance and depth of the ground copper tubing DX condenser in a single and two-loop configuration were investigated using a hypothetical (3.5) kW cooling unit with (3.6) COP. As predicted by these connections, there was a lot of scatter in the borehole thermal resistance and depth. For the single and double U-tube geometries studied, it was up to twice as much. The main finding of this research was that these correlations should only be used in the preliminary thermal design of ground source heat pumps (GSHPs). Because of the large range of variability in their projections, they can’t be used for a finished thermal structure of the borehole unless they’re backed up by experimental evidence. The borehole configuration, tube diameter (do), tube center-center spacing (Sp), and borehole size all indicated strong interactions (DB). Increasing the grout thermal conductivity improves the borehole’s thermal performance and reduces the depth for given operating circumstances, according to all of the models studied.
Author (S) Details
Ali H. Tarrad
Université de Lorraine, CNRS, LEMTA, F-54000 Nancy, France.
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