Numerical study on the effects of design parameters on the heat transfer performance of coaxial deep borehole heat exchanger
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Date:
2025-04-30Title of Paper:
Numerical study on the effects of design parameters on the heat transfer performance of coaxial deep borehole heat exchangerJournal:
International Journal of Energy ResearchSummary:
Deep borehole heat exchanger (DBHE) is attracting attention intensively owing
to much more geothermal extraction, higher efficiency for heat pumps, and
lesser land demand compared with shallow borehole heat exchanger. DBHE
is usually dipped into several thousand meters in the subsurface, having a com-
plicated heat transfer with surrounding rock–soil. However, the heat transfer
characteristics below surface under different conditions are rarely studied. In
this study, a numerical model considering the comprehensive effects of geo-
thermal gradients and heat loss from inner pipe was proposed. The model
was validated with experimental data and Beier analytical solution. Based on
the model, the effects of primary design parameters on the heat transfer perfor-
mance below surface along the pipe were investigated. The results indicate that
temperature at pipe bottom increases with inlet flow rate decreasing, while the
heat load cannot be extracted fully to the surface because of the heat loss of
inner pipe. When the inlet flow rates decrease from 41.39 to 4.52 m 3 /h, the heat
loss ratio increases from 25.5% to 63.7%. It is an effective way of insulating
inner pipe to reduce heat loss under low inlet flow rates. Increasing the velocity
in inner pipe by lessening the inner pipe diameter can also decline the heat loss
well. While by this way, the increasing pumping power resulting from the
higher velocity in inner pipe has to be considered. This study is significant to
effective optimization of DBHE and energy conservation of buildings.Co-author:
Jun Liu, Fenghao Wang*, Wanlong Cai, Zhihua Wang, Qingpeng Wei, Jiewen DengVolume:
2019Page Number:
1-16Translation or Not:
NoDate of Publication:
2019-01-28
