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Old 01-02-19, 05:41 AM   #5
DoctorDoctor
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I am not quite sure what you mean about pressure drop. The beauty of (relatively) low flow through large diameter pipes is that the flow is governed by Bernoulli's equation. Now Bernoulli's equation doesn't really care what is in the middle (large pipes, changes in height, splits and joining of the conduit, etc), only the beginning and end. The pressure drop for input 2 inch pipe and output 2 inch pipe (with intervening plumbing as I sketched) would be by Bernoulli's equation be 0. Of course, in the real world, there is some friction and some non-laminar flow but not much.

This contrasts the loopy trench field geothermal technique where you are trying to push fluid through a very long and relatively narrow tube. In that case, friction is very significant.

As to the second part of your comment, again I am confused. Geothermal is all about engaging dirt to exchange heat. By using the vertical nature you bring in a lot of volume of earth. The low flow of the outer pipe would improve the heat exchange. But the really important factor is the surface area difference.
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