| 摘要 |
The geothermal probe has a central return tube (7) bringing back a water flow from the subterranean depths below, to e.g. a surface heat pump. Deep in the earth, the head (3) connects the surrounding downward flow tubes (5) to the return. The tubes are of pressure resistant plastic. The available cross-section of the return tube is less than 2/3 the sum of cross-sectional areas of the flow tubes. Preferably the cross-section of the return tube is one half the sum of the cross-sections of the flow tubes. Return and flow tubes are designed for the same nominal pressure. The return tube accordingly has greater thickness than the flow tubes. There may be eight flow tubes, the cross-section of the return tube (7) being half the sum of the cross-sections of the flow tubes. The flow tubes have an ID of about 20mm, pref. 20.4mm, the return tubes have an ID of about 40mm, pref. 40.8mm, and the wall thickness of the return tube is about twice that of the flow tubes. Correspondingly, the length may exceed 140m, or 200m.
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