Experimental Investigation of Nano Particle Effect on Heat Transfer in a Micro Heat Exchanger

Jafarpoor Chekab, Hamideh | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40718 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Shafii, Mohammad Behshad; Saidi, Mohammad Hassan; Saeedi, Mohammad Saeed
  7. Abstract:
  8. Modern microelectronic systems generate a large amount of heat which must be transferred out of the system without excessive temperature rise. Conventional forced air convection and microchannel cooling plates have reached their performance limits Nanofiuids are proposed as an innovative way to solve the problem. A nanofiuid is nanoscale solid particles dispersed in a traditional heat transfer liquid. Some studies show an anomalous increase in the thermal conductivity for stationary nanofiuids. However, there are only few previous studies on the convection heat transfer rate and viscosity of nanofiuids. Both convection and stationary measurements of the thermal conductivity are widely scattered, so it is not known if nanofiuids will be useful in electronic cooling applications. Here, taking into account that microfabrication of micro devices is a new area in Iran, different methods of microfabrication have been reviewed and some emerging phenomena in micro scale have been introduced. Following that, micro channels and nanofluids have been investigated. Standard microfabrication process for fabricating microchannels and at the end, the micro heat exchanger itself is presented. Experiments for investigation of forced convective heat transfer in fabricated microchannels which are triangle type with hydraulic diameter of 94.7 microns and 1.111 aspect ratio, have been performed using in deionized water as cooling fluid. The channels are made of silicon and glass and are fabricated by MEMS technology. Simultanouesly, experiments have been simulated numerically in Fluent software. The experimental results reveal a 0 to 50 percent improvement in convective heat transfer in micro channels for 1 to 4 percent volumetric concentration nanofluid in comparison with water. Furthermore, comparing experimental and theoretical results, it can be concluded that in addition to nanofluid conductivity increase, another mechanism must be involved in the increasing of heat transfer coefficient because experimental result shows a much higher increase than the numerical predictions. The amounts of for in deionized water nanofluid have been calculated according to experimental results which are between 1 and 30 for concentrations 1 to 4 percents respectively.
  9. Keywords:
  10. Convection Heat Transfer ; Nanofluid ; Microchannel ; Heat Transfer Coefficient

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