Change search
ReferencesLink to record
Permanent link

Direct link
Development of heat pipes with potassium as woking fluid: Performance limitations and test rig development
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Energy and Process Engineering.
2012 (English)MasteroppgaveStudent thesis
Abstract [en]

The incentive to reduce energy consumption in the industry is big, especially in high temperature systems. Heat pipes are of great interest for this purpose due to their favorable thermomechanical properties. This master thesis is a part of the ongoing study of Ph.D. candidate Geir Hansen, who is currently developing a rectangular heat pipe with potassium as working fluid at NTNU. The rectangular heat pipe is intended to be implemented in the walls of electrolysis cells as a part of a heat recovery system. The present work reports results of theoretical calculations of two important heat transfer limitations, the incipience of boiling and the capillary limitation for two types of nickel foam wicks. Results of experimental tests carried out on the cooling circuit for the proposed rectangular heat pipe are also reported. The foam porosity, permeability and effective pore radius for wick 1 is 0.797, 31·10−12m2 and 62·10−6m, respectively, and for wick 2; 0.886, 205·10−12m2 and 126·10−6m. A literature survey showed that porous coated surfaces improves the heat transfer and requires less superheat for boiling to commence. Calculations performed showed no danger of homogeneous nucleation in the proposed heat pipe. Boiling inside the nickel foam wick(s) were found to only be of concern for wick 2 at high heat fluxes and a operating temperature of 600C. Calculations of the capillary limit showed that wick 2 is the best choice for sustaining high heat fluxes. Increasing the wick length to 20cm made wick 2 not suitable for usage, and wick 1 was the best choice for increased wick length. Combination of the two wick types showed to be very effective and significantly (factor of almost 4) improved the performance. An uneven heat flux distribution where a lower heat flux is at the bottom region of the evaporator is found to lower the performance, while a higher heat flux at the bottom region increases the performance. Early tests revealed that the PID controller was marginally stable, so the controller was tuned and stable operating conditions were achieved. Experiments showed that in order to get an accurate heat balance for the test rig, knowledge about the exact position of the thermocouples is needed.

Place, publisher, year, edition, pages
Institutt for energi- og prosessteknikk , 2012. , 140 p.
Keyword [no]
ntnudaim:8178, MTPROD produktutvikling og produksjon, Energi-, prosess- og strømningsteknikk
URN: urn:nbn:no:ntnu:diva-18600Local ID: ntnudaim:8178OAI: diva2:566114
Available from: 2012-11-08 Created: 2012-11-08

Open Access in DiVA

fulltext(8220 kB)2688 downloads
File information
File name FULLTEXT01.pdfFile size 8220 kBChecksum SHA-512
Type fulltextMimetype application/pdf
cover(184 kB)24 downloads
File information
File name COVER01.pdfFile size 184 kBChecksum SHA-512
Type coverMimetype application/pdf

By organisation
Department of Energy and Process Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 2688 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: 172 hits
ReferencesLink to record
Permanent link

Direct link