| Title |
Heat transfer augmentation in rectangular micro channel covered with vertically aligned carbon nanotubes |
| ID_Doc |
64167 |
| Authors |
Taha, TJ; Lefferts, L; van der Meer, TH |
| Title |
Heat transfer augmentation in rectangular micro channel covered with vertically aligned carbon nanotubes |
| Year |
2016 |
| Published |
|
| Abstract |
An experimental heat transfer investigation was carried out to examine the influence of carbon nanotubes (CNTs) layer deposits on the convective heat transfer performance inside rectangular microchannels. Successful synthesis of vertically aligned CNTs was achieved using a catalytic vapor deposition (CVD) process on a silicon sample substrate. By varying the synthesis time, on average 6 mu m and 20 mu m thick layers of CNTs were made with surface roughness of (S-a = 1.062 mu m, S-q = 1.333 mu m) and (S-a = 0.717 mu m, S-q = 0.954 mu m) respectively. The external surface area of the samples increased 7 times compared to the bare silicon chip. The heat transfer performance of each sample was measured inside two rectangular microchannels with cross-section of 125 mu m x 9 mm and 200 mu m x 9 mm. For the 125 mu m channel height, the 6 mu m and 20 mu m thick layer of CNTs resulted in 12% and 26% increase in pressure drop respectively. The pressure drop obtained from the 200 gm channel height show a similar trend with an increase of 6% and 16.4% for 6 mu m and 20 mu m CNTs layer thickness respectively. An average heat transfer enhancement of 19% and 74% is obtained inside the 125 mu m height microchannel with 6 mu m and 20 mu m CNTs layer thickness respectively. Whereas, the average heat transfer enhancement of 22% and 62% are obtained inside the 200 mu m channel with respective CNTs layer thicknesses of 6 mu m and 20 mu m. Enhancements are attributed to an increase in surface area and effective thermal conductivity inside the thermal boundary layer. However, the frictional heating (viscous dissipation) of a particular nanostructured sample increases with a decrease in channel height. This difference in channel size results in stronger competition between heat transfer enhancement potential that can be achieved by the deposited surface and the decrease in Nusselt number due to viscous dissipation. (C) 2016 Elsevier Ltd. All rights reserved. |
| PDF |
https://research.utwente.nl/files/6568812/heat.pdf
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