Numerical Investigation of a Crossflow Jet in a Rectangular Microchannel

2013 ◽  
Vol 284-287 ◽  
pp. 849-853
Author(s):  
Kok Cheong Wong

The present numerical study is conducted in three dimensional to investigate the crossflow of an external round jet and a horizontal stream of microchannel flow. The results of heat transfer performance for the cases with and without transverse jet are compared. The patterns of different crossflow jet were analyzed to understand the flow and heat transfer characteristics. The effect of jet nozzle position on the heat transfer is investigated. Generally, the heat transfer performance increases with the jet Reynolds number. However, some cases of weak jet are found to cause lower heat transfer rate relative to the case without external jet. When vertical weak jet encounter strong horizontal flow, the horizontal flow is dominant that the jet cannot reach the microchannel bottom wall but imposes resistance to the horizontal flow. The investigation on the jet nozzle location shows that the jet nozzle location closer to the channel inlet gives better heat transfer performance.

2015 ◽  
Vol 26 (12) ◽  
pp. 1550140 ◽  
Author(s):  
Amin Ebrahimi ◽  
Ehsan Roohi

Flow patterns and heat transfer inside mini twisted oval tubes (TOTs) heated by constant-temperature walls are numerically investigated. Different configurations of tubes are simulated using water as the working fluid with temperature-dependent thermo-physical properties at Reynolds numbers ranging between 500 and 1100. After validating the numerical method with the published correlations and available experimental results, the performance of TOTs is compared to a smooth circular tube. The overall performance of TOTs is evaluated by investigating the thermal-hydraulic performance and the results are analyzed in terms of the field synergy principle and entropy generation. Enhanced heat transfer performance for TOTs is observed at the expense of a higher pressure drop. Additionally, the secondary flow generated by the tube-wall twist is concluded to play a critical role in the augmentation of convective heat transfer, and consequently, better heat transfer performance. It is also observed that the improvement of synergy between velocity and temperature gradient and lower irreversibility cause heat transfer enhancement for TOTs.


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