Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The Use of a Nano- and Microporous Surface Layer to Enhance Boiling in a Plate Heat Exchanger
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.ORCID iD: 0000-0002-9902-2087
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.ORCID iD: 0000-0001-5678-5298
Show others and affiliations
2009 (English)In: Journal of heat transfer, ISSN 0022-1481, E-ISSN 1528-8943, Vol. 131, no 10Article in journal (Refereed) Published
Abstract [en]

Presented research is an experimental study of the performance of a standard plate heat exchanger evaporator, both with and without a novel nano- and microporous copper structure, used to enhance the boiling heat transfer mechanism in the refrigerant channel. Various distance frames in the refrigerant channel were also employed to study the influence of the refrigerant mass flux on two-phase flow heat transfer. The tests were conducted at heat fluxes ranging between 4.5 kW/m(2) and 17 kW/m(2) with 134a as refrigerant. Pool boiling tests of the enhancement structure, under similar conditions and at various surface inclination angles, were also performed for reasons of comparison. The plate heat exchanger with the enhancement structure displayed up to ten times enhanced heat transfer coefficient in the refrigerant channel, resulting in an improvement in the overall heat transfer coefficient with over 100%. This significant boiling enhancement is in agreement with previous pool boiling experiments and confirms that the enhancement structure may be used to enhance the performance of plate heat exchangers. A simple superposition model was used to evaluate the results, and it was found that, primarily, the convective boiling mechanism was affected by the distance frames in the standard heat exchanger. On the other hand, with the enhanced boiling structure, variations in hydraulic diameter in the refrigerant channel caused a significant change in the nucleate boiling mechanism, which accounted for the largest effect on the heat transfer performance.

Place, publisher, year, edition, pages
2009. Vol. 131, no 10
Keyword [en]
boiling, convection, evaporation, flow through porous media, heat, exchangers, microchannel flow, nanofluidics, nucleation, refrigerants, two-phase flow, small-diameter channels, refrigerant vaporization, flow
Identifiers
URN: urn:nbn:se:kth:diva-18668DOI: 10.1115/1.3180702ISI: 000268749900011Scopus ID: 2-s2.0-77955289061OAI: oai:DiVA.org:kth-18668DiVA: diva2:336715
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Enhanced Boiling Heat Transfer on a Dendritic and Micro-Porous Copper Structure
Open this publication in new window or tab >>Enhanced Boiling Heat Transfer on a Dendritic and Micro-Porous Copper Structure
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A novel surface structure comprising dendritically ordered nano-particles of copper was developed during the duration of this thesis research project. A high current density electrodeposition process, where hydrogen bubbles functioned as a dynamic mask for the materials deposition, was used as a basic fabrication method. A post processing annealing treatment was further developed to stabilize and enhance the mechanical stability of the structure.

The structure was studied quite extensively in various pool boiling experiments in refrigerants; R134a and FC-72. Different parameters were investigated, such as; thickness of the porous layer, presence of vapor escape channels, annealed or non-annealed structure. Some of the tests were filmed with a high speed camera, from which visual observation were made as well as quantitative bubble data extracted. The overall heat transfer coefficient in R134a was enhanced by about an order of magnitude compared to a plain reference surface and bubble image data suggests that both single- and two-phase heat transfer mechanisms were important to the enhancement.

A quantitative and semi-empirical boiling model was presented where the main two-phase heat transfer mechanism inside the porous structure was assumed to be; micro-layer evaporation formed by an oscillating vapor-liquid meniscus front with low resistance vapor transport through escape channels. Laminar liquid motion induced by the oscillating vapor front was suggested as the primary single-phase heat transfer mechanism.

The structure was applied to a standard plate heat exchanger evaporator with varying hydraulic diameter in the refrigerant channel. Again, a 10 times improved heat transfer coefficient in the refrigerant channel was recorded, resulting in an improvement of the overall heat transfer coefficient with over 100%. A superposition model was used to evaluate the results and it was found that for the enhanced boiling structure, variations of the hydraulic diameter caused a change in the nucleate boiling mechanism, which accounted for the largest effect on the heat transfer performance. For the standard heat exchanger, it was mostly the convective boiling mechanism that was affected by the change in hydraulic diameter.

The structure was also applied to the evaporator surface in a two-phase thermosyphon with R134a as working fluid. The nucleate boiling mechanism was found to be enhanced with about 4 times and high speed videos of the enhanced evaporator reveal an isolated bubble flow regime, similar to that of smooth channels with larger hydraulic diameters. The number and frequency of the produced bubbles were significantly higher for the enhanced surface compared to that of the plain evaporator. This enhanced turbulence and continuous boiling on the porous structure resulted in decreased oscillations in the thermosyphon for the entire range of heat fluxes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 75 p.
Series
Trita-REFR, ISSN 1102-0245 ; 11:02
Keyword
enhanced boiling; R134a; FC-72; flow boiling; heat transfer; high speed visualization; instability; micro-channels; micro-structured; nano- and micro-technology; nano- and micro-porous structured surfaces; plate heat exchanger; pool boiling; porous media; thermosyphon; two-phase heat transfer
National Category
Energy Engineering
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-47538 (URN)978-91-7501-163-9 (ISBN)
Public defence
2011-11-25, E1, Lindstedtsvägen 3, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
StandUp
Note
QC 20111111Available from: 2011-11-11 Created: 2011-11-10 Last updated: 2011-11-11Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Palm, Björn E.Toprak, Muhammet S.

Search in DiVA

By author/editor
Furberg, RichardPalm, Björn E.Li, ShanghuaToprak, Muhammet S.Muhammed, Mamoun
By organisation
Applied Thermodynamics and RefrigerationFunctional Materials, FNM
In the same journal
Journal of heat transfer

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 239 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf