Benefits of spanwise gaps in cylindrical vortex generators for conjugate heat transfer enhancement in micro-channels

Cylindrical vortex generators placed transversely over the span of a micro-channel can enhance heat transfer performance, but adding full-span vortex generators incurs a substantial pressure drop penalty. This paper examines the benefits of introducing various gaps along the length of the vortex gen...

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Bibliographic Details
Published in:Applied thermal engineering 2018-02, Vol.130, p.571-586
Main Authors: Al-Asadi, Mushtaq T., Alkasmoul, Fahad S., Wilson, Mark C.T.
Format: Article
Language:English
Subjects:
Computational fluid dynamics
Cooling
Finite element method
Fluid flow
Gap effect
Heat flux
Heat transfer
Heat transfer enhancement
Hydraulics
Longitudinal and transverse vortices
Micro-channel
Micro-scale cooling system
Performance evaluation
Pressure drop
Resistance
Reynolds number
Thermal conductivity
Thermal hydraulic performance
Vortex generators
Vortices
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Summary:Cylindrical vortex generators placed transversely over the span of a micro-channel can enhance heat transfer performance, but adding full-span vortex generators incurs a substantial pressure drop penalty. This paper examines the benefits of introducing various gaps along the length of the vortex generators, both for reducing pressure drop and improving the thermal conductance of the system. Three particular configurations are considered with varied dimensions: symmetrical gaps at each end of the vortex generator, i.e. adjacent to the channel side walls; a single central gap; and a combination of a central and end gaps. The performance is investigated numerically via 3D finite element analysis for Reynolds number in the range 300–2300 and under conditions of a uniform heat flux input relevant to microelectronics cooling. Results demonstrate that having end gaps alone substantially improves heat transfer while reducing the pressure drop. As well as generating longitudinal vortices which draw heat from the adjacent channel side walls, hot fluid passing through the gaps is swept directly upwards and inwards into the bulk flow, where it remains as it flows to the outlet. A thermal-hydraulic performance evaluation index is improved from 0.7 for full-span vortex generators to 1.0 with end gaps present. The central and central-plus-end gap geometries are less effective overall, but do offer localised improvements in heat transfer.
ISSN:1359-4311
1873-5606
DOI:10.1016/j.applthermaleng.2017.10.157