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Table 1 Range of each parameter used for borehole thermal resistance calculation
From: Designing coaxial ground heat exchangers with a thermally enhanced outer pipe
Parameter | Minimum | Maximum | Average |
|---|---|---|---|
Water flow rate (L s−1) | 0.5 | 6 | 3.25 |
Borehole length (m) | 50 | 250 | 150 |
Backfilling thermal conductivity (W m−1 K−1) | 0.6 | 2.8 | 1.7 |
Pipe thermal conductivity (W m−1 K−1) | 0.1 | 0.7 | 0.4 |
Pipe outside diameter (mm)/thickness (mm) | SDR-11 | SDR-17 | SDR-13.5 |
31.75-mm (1.25 in.) nominal diameter | 42.0/3.8 | Not used for U-pipe | Not used for U-pipe |
50.8-mm (2 in.) nominal diameter | 59.7/5.5 | 60.3/3.6 | 59.8/4.5 |
101.6-mm (4 in.) nominal diameter | 113.1/10.4 | 114.3/6.7 | 113.3/8.5 |
152.4-mm (6 in.) nominal diameter | 166.4/15.3 | 168.3/9.9 | 166.8/12.5 |