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Table 1 Parameters in the numerical model

From: Numerical investigation on the performance, sustainability, and efficiency of the deep borehole heat exchanger system for building heating

Parameter Symbol Value Unit
Borehole length L 2600 m
Borehole diameter 2\(r_{\text{b}}\) 216 mm
Diameter of inner pipe 2\(r_{\text{i}}\) 110 mm
Wall thickness of inner pipe \(t_{\text{i}}\) 7.34 mm
Diameter of outer pipe 2\(r_{\text{o}}\) 178 mm
Wall thickness of outer pipe \(t_{\text{o}}\) 5.87 mm
Thermal conductivity of inner pipe wall \(\lambda _{\text{i}}\) 0.21 W m−1 K−1
Thermal conductivity of outer pipe wall \(\lambda _{\text{o}}\) 1.3 W m−1 K−1
Soil and rock thermal conductivity \(\lambda _{{\text{s}}}\) 2.5 W m−1 K−1
Heat capacity of soil/rock \(\rho _{\text{s}}\) \(c_{{{\text{s}}}}\) \(2.24\times 10^{6}\) J m−3 K−1
Thermal conductivity of grout \(\lambda _{\text{g}}\) 1.3 W m−1 K−1
Heat capacity of grout \(\rho _{\text{g}}\) \(c_{\text{g}}\) \(3.8\times 10^{6}\) J m−3 K−1
Thermal conductivity of circulating fluid \(\lambda _{\text{r}}\) 0.59 W m−1 K−1
Heat capacity of circulating fluid \(\rho _{\text{r}}c_{\text{r}}\) \(4.19\times 10^{6}\) J m−3 K−1
Viscosity of circulating fluid \(\mu _{\text{r}}\) \(1.14\times 10^{-3}\) kg m−1 s−1
Flow rate of circulating fluid \(Q_{\text{r}}\) \(8.33\times 10^{-3}\) m3 s−1