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

Geothermal Energy

Science – Society – Technology

Table 3 Different outer pipe materials with different inner pipes

Scenario ID	Inner pipe wall thermal conductivity (W m⁻¹ K⁻¹)	Outer pipe wall thermal conductivity (W m⁻¹ K⁻¹)	Description
1A	0.5	1.3	Concrete outer pipe without heat insulation layer on the inner pipe
1B	0.1	1.3	Concrete outer pipe with heat insulation layer on the inner pipe
1C	0.5	20	Steel outer pipe without heat insulation layer on the inner pipe
1D	0.1	20	Steel outer pipe with heat insulation layer on the inner pipe