Change search
ReferencesLink to record
Permanent link

Direct link
Värmeöverföring i bergvärmesystem: En numerisk analys av den ringformade koaxiala borrhålsvärmeväxlaren
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2012 (Swedish)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesisAlternative title
Heat transfer in ground source heat pump systems : A numerical analysis of the annular coaxial borehole heat exchanger (English)
Abstract [en]

The borehole heat exchangers of today suffer from poor thermal and hydrodynamic performance. The purpose of this thesis is to improve the performance of ground source heat pump systems and thermal energy storages by increasing the energy efficiency of the borehole heat exchangers. For this reason, the annular coaxial borehole heat exchanger (CBHE) has been analyzed. This type of heat exchanger is interesting in terms of both thermal and hydrodynamic performance. A model has been set up in the program Comsol Multiphysics in order to investigate the heat transfer characteristics along the borehole. A literature survey that summarizes the analytical calculation methods developed in earlier Swedish research is presented in the report. Different geometries with or without insulation of the central pipe have been analyzed and the effective borehole resistance for each geometry has been calculated based on the simulation results. The model has been validated against a recently performed thermal response test, and shows very good correlation with reality. The results from the simulations show that by using the annular CBHE an increase of 2-3 °C in the evaporator of the heat pump can be achieved. Calculations show that the pump work (head loss) can be reduced to 1/6 of the corresponding case with a single U-pipe. There arises a vertical temperature gradient in the bedrock when recharging and extracting heat with the annular CBHE. This means that the annular CBHE acts like a counter-flow heat exchanger which is thermally optimal. In total, the simulation result shows that the annular CBHE geometry in this thesis can increase a system's seasonal performance factor (SPF) with 10-19 % in comparison with a U-pipe BHE. This is equivalent to 10-19 % lower electrical power consumption every year.

Place, publisher, year, edition, pages
2012. , 92 p.
UPTEC ES, ISSN 1650-8300 ; 12016
Keyword [en]
annular coaxial borehole heat exchanger, ground source heat pump, BHE, CBHE, thermal borehole resistance
Keyword [sv]
Koaxial borrhålsvärmeväxlare, borrhålsmotstånd, värmepump, bergvärme, bergkyla, termisk prestanda
National Category
Energy Engineering
URN: urn:nbn:se:uu:diva-176915OAI: diva2:537799
Educational program
Master Programme in Energy Systems Engineering
Available from: 2012-08-08 Created: 2012-06-27 Last updated: 2012-08-08Bibliographically approved

Open Access in DiVA

fulltext(4405 kB)666 downloads
File information
File name FULLTEXT01.pdfFile size 4405 kBChecksum SHA-512
Type fulltextMimetype application/pdf

By organisation
Energy Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 666 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 526 hits
ReferencesLink to record
Permanent link

Direct link