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
Nature-inspired boiling enhancement by novel nanostructured macroporous surfaces
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.ORCID iD: 0000-0001-5678-5298
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.ORCID iD: 0000-0002-9902-2087
Show others and affiliations
2008 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 18, no 15, 2215-2220 p.Article in journal (Refereed) Published
Abstract [en]

World energy crisis has triggered more attention to energy saving and energy conversion systems. Enhanced surfaces for boiling are among the applications of great interest since they can improve the energy efficiency of heat pumping equipment (i.e., air conditioners, heat pumps, refrigeration machines). Methods that are used to make the state-of-the-art enhanced Surfaces are often based on complicated mechanical machine tools, are quite material-consuming and give limited enhancement of the boiling heat transfer. Here, we present a new approach to fabricate enhanced surfaces by using a simple electrodeposition method with in-situ grown dynamic gas bubble templates. As a result, a well-ordered 3D macro-porous metallic surface layer with nanostructured porosity is obtained. Since the structure is built based on the dynamic bubbles, it is perfect for the bubble generation applications Such as nucleate boiling. At heat flux of 1W cm(-2), the heat transfer coefficient is enhanced over 17 times compared to a plain reference Surface. It's estimated that such ail effective boiling surface Would improve the energy efficiency of many heat Pumping machines with 10-30%. The extraordinary boiling performance is explained based on the structure characteristics.

Place, publisher, year, edition, pages
2008. Vol. 18, no 15, 2215-2220 p.
Keyword [en]
heat-transfer, saturated fc-72, silicon, walls
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-17788DOI: 10.1002/adfm.200701405ISI: 000258795500009Scopus ID: 2-s2.0-50249158588OAI: oai:DiVA.org:kth-17788DiVA: diva2:335833
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Fabrication of Nanostructured Materials for Energy Applications
Open this publication in new window or tab >>Fabrication of Nanostructured Materials for Energy Applications
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

World energy crisis has triggered more attention to energy saving and energy conversion systems with high efficiency. There is a growing awareness that nanoscience and nanotechnology can have a profound impact on energy generation, conversion, and recovery. Nanotechnology-based solutions are being developed for a wide range of energy problems such as, solar electricity, hydrogen generation and storage, batteries, fuel cells, heat pumps and thermoelectrics. This thesis deals with the design and fabrication of novel functional materials/architectures for energy-related applications. The study includes two parts: Nanostructured thermoelectric (TE) materials for energy conversion and nanostructured metallic surfaces for energy heat transfer.

In the first part, the focus is given to the fabrication of novel nanostructured TE materials and architectures. TE materials are very important functional materials that can convert heat to electrical energy and vice versa. Recently, nanostructuring TE materials showed very promising potential to improve their TE figure of merit which opens a new venue for the TE world. As a result, some advanced nanostructured TE architectures are proposed as the state-of-the-art TE materials/structures. Among these advanced TE architectures, bismuth telluride nanowires/thick films and skutterudite nanocomposites with nanoinclusions have been successfully fabricated and some of their advantageous TE performance has been demonstrated. For example, an improvement of 11% on the figure of merit, ZT, was achieved in the CoSb3 nanocomposite with 5 mole% ZrO2 as nanoinclusion. Comprehensive physico-chemical characterization techniques have been used for the synthesized TE materials. The potential-Seebeck microprobe, 4-point probe and laser flash apparatus have been used for the measurement of TE parameters on the TE materials.

In the second part of the thesis, we developed a nanostructured macro-porous (NMp) surface for enhancing heat transfer in boiling process. Enhanced surfaces for boiling improve the energy efficiency of heat pumping equipment such as air conditioners, refrigerators, etc. Conventional techniques currently used for fabricating enhanced surfaces are often based on the use of complicated mechanical machine tools and require a large consumption of materials and give only limited enhancement of the boiling heat transfer. In this thesis, we present a new approach to fabricate enhanced surfaces by using electrodeposition under specific conditions forming in-situ dynamic gas bubble templates. As a result, the NMp metallic surface layer comprising of dendritically ordered copper branches is obtained. Since the structure is formed during the evolution of the dynamic bubbles, it is ideal for the bubble generation applications such as boiling. The efficiency of the NMp surfaces for boiling heat transfer was evaluated in pool boiling experiments. At the heat flux of 1 W/cm2, the heat transfer coefficient for the NMp surface is found to be more than 17 times higher than the reference surface. It's estimated that such an effective boiling surface would improve the energy efficiency of many heat pumping machines with 10 - 30 %. The extraordinary enhancement of boiling performance is explained by the structure characteristics, which assist in enhancing nucleation of the gas bubbles, subsequent coalescence, and facilitated departure from the surfaces.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. x, 72 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2008:12
Keyword
Materials Chemistry
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-4807 (URN)978-91-7178-994-5 (ISBN)
Public defence
2008-06-13, Sal N1, KTH-Electrum 3, Isafjordsgatan 28 A/D, Kista, 10:00
Opponent
Supervisors
Note
QC 20100924Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2010-09-24Bibliographically approved
2. 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

Toprak, Muhammet S.Palm, Björn E.

Search in DiVA

By author/editor
Li, ShanghuaFurberg, RichardToprak, Muhammet S.Palm, Björn E.Muhammed, Mamoun
By organisation
Functional Materials, FNMApplied Thermodynamics and Refrigeration
In the same journal
Advanced Functional Materials
Materials Chemistry

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 184 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