downhole heat exchanger
{{Short description|Type of heat exchanger}}
File:Erdwaermesondenbohrung01.JPG
File:Unteres Ende einer Erdwärmesonde.jpg
File:Oberes Ende einer Erdwärmesonde.jpg
A downhole heat exchanger, (DHE) also called a borehole heat exchanger, (BHE) is a heat exchanger installed inside a vertical or inclined borehole.{{cite web |url=http://geoheat.oit.edu/bulletin/bull20-3/art1.pdf |title=Downhole Heat Exchangers |publisher=Geo-Heat Center - Oregon Institute of Technology |access-date=21 April 2013 |archive-date=17 February 2012 |archive-url=https://web.archive.org/web/20120217184548/http://geoheat.oit.edu/bulletin/bull20-3/art1.pdf |url-status=dead }} It is used to capture or dissipate heat to or from the ground. DHT's are used for geothermal heating, sometimes with the help of a geothermal heat pump. Downhole heat exchangers, like other use of geothermal energy, have the potential to significantly contribute to the reduction of {{CO2}} emissions.{{Cite web|title=Geothermal Energy - Professur für Geothermal Technologies|url=https://www.bgu.tum.de/en/gtt/research/geothermal-energy/|access-date=2021-01-15|website=www.bgu.tum.de}} In northern Europe, DHE are already widely deployed.https://www.mbie.govt.nz/assets/14861fe5a3/geothermal-barriers-update-1.pdf {{Bare URL PDF|date=March 2022}}
Types
=U-tube=
The heat exchanger usually consists of one or two u-tubes through which the carrier fluid, usually water, circulates. The space around the u-tubes is filled with groundwater or backfilled with thermally conductive grout.
=Open pipe=
Another design uses a single open pipe to flow water downward. The water then returns through the annular gap between the pipe and the casing. This design provides better thermal contact than u-tubes, but risks contamination by groundwater. Since this involves practically no downhole equipment, these systems usually only go by the name of borehole heat exchangers (BHT).
=Standing column well=
If no casing is installed and groundwater is permitted to charge the system, this arrangement is no longer a BHT, but rather a standing column well.
External links
- Video documentation: [https://vimeo.com/72978861 Installation of a downhole heat exchanger]
- John W. Lund: [https://www.geothermal-energy.org/pdf/IGAstandard/EGC/szeged/O-7-08.pdf The use of downhole heat exchangers (2003)]