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Table 2 Design parameters of 2U-type BHE

From: Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

Parameter/symbol (unit) Value
BHE depth/H (m) 80
Borehole diameter/ψ (m) 0.13
Outer diameter of branch pipe-in(out)/di(o) (m) 0.032
Wall thickness of branch pipe-in(out)/bi(o) (m) 0.0029
Adjacent branch pipe distance/w (m) 0.05
Thermal conductivity of pipe-in(out) material/λpi(o) (W m−1 K−1) 0.60
Thermal conductivity of refrigerant (water)/λr (W m−1 K−1) 0.65
Volumetric heat capacity of refrigerant (water)/crρr (J m−3 K−1) 4.18 × 106
Volumetric heat capacity of grout/cgρg (J (m−3 K−1)) 2.19 × 106
Thermal conductivity of grout/λg (W m−1 K−1) 1.90