3150 -- Effect of Axial Spacing Variation of Underground Pipe Loop on Condenser Heat Transfer PDF

A numerical simulation was performed to study the effect of axial spacing variation between two legs of a U-bend pipe on heat dissipation, used for condenser heat transfer, in a closed-loop water-cooled earth-coupled heat pump. Three problems were studied. The first used a uniform conductivity model, and the second one assumed: a linear relationship of soil conductivity with temperature. By assuming uniform but different average outside pipe surface and earth temperatures, it was found that an increase of 20% in heat transfer, over the base case of pipes touching each other, can be achieved by spacing the pipes about 0.18 m apart. A transient analysis showed increases on the order of 40% over the base case. A spacer design using materials similar to the pipe is suggested to keep a uniform spacing, and it will also help in curbing "thermal leakage" between the two legs of the loop.

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