Thermal enhancement in a microchannel heat sink using passive methods / Navin Raja Kuppusamy
The present work focuses on enhancing the thermal performance of the microchannel heat sink (MCHS) using the passive method. Computational domain of the single channel was selected from the physical model of the MCHS for the numerical simulation. The basic geometry of the computational domain was...
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| Format: | Thesis |
| Published: |
2016
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| Online Access: | http://studentsrepo.um.edu.my/6789/ http://studentsrepo.um.edu.my/6789/1/navin.pdf |
| Summary: | The present work focuses on enhancing the thermal performance of the microchannel
heat sink (MCHS) using the passive method. Computational domain of the single
channel was selected from the physical model of the MCHS for the numerical
simulation. The basic geometry of the computational domain was taken from the
geometry of the MCHS from existing literatures. This model was validated with the
available analytical correlation and existing numerical results.
Five types of passive enhancements were studied in this study. Those methods are;
(1) secondary channel, (2) micromixer, (3) constrictions, (4) re-entrant obstruction and
(5) cavities. The fluid flow and heat transfer characteristics of all these MCHS were
numerically investigated in a laminar and steady state condition at a constant heat flux.
The effect of the geometrical parameter on the thermal and pressure loss was studied at
different flow configurations. The results showed that passive enhancements of the
MCHS significantly improved compared to the simple MCHS.
There were a few highlights that were also gathered from this study. Firstly, the
performance of secondary flow and micromixer is immensely good where heat transfer
increased up to 1.43 times compare to simple MCHS. Furthermore, the pressure drop
associated with this enhancement was in fact lower than the simple MCHS (0.97 times
that of simple MCHS). Secondly, although constrictions and the re-entrant obstruction
improved the performance of the MHCS by 2.25 and 1.2 respectively, the pressure loss
associated with this enhancement was substantially high. Finally, the convection heat
transfer in the MCHS with cavities improved considerably up to 1.63 with a negligible
pressure drop.
It was also found that the performance of the MCHS was greatly dependent on the
geometrical parameters of passive enhancement except for the constrictions and reentrant obstructions. Such improvement attributes to the increase of the heat transfer
area and the repetitive development of the boundary layers. Besides that, the passive
enhancement also enhanced the fluid mixing. For instance, the large and intense vortices
observed in the cavities, the micromixers and secondary channels resulted in chaotic
advection that ultimately improved the convection heat transfer. Similarly, the Eddy
effect in the MCHS with constriction also improved the heat transfer. The jet and
throttling effect, as well as the fluid acceleration that the fluid experienced after passing
the modified section also contributed to the enhancement of heat transfer with some
pressure drop penalty.
The overall result of the present work shows that the MCHS with passive
enhancement has a high potential and is feasible to be implemented in practical
applications. |
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