Three-dimensional flow effects on forced convection heat transfer in a channel with stepwise-varying width

• Published in: International journal of thermal sciences 2013-05, Vol.67, p.177-191
• Main Authors: Karathanassis, I.K., Papanicolaou, E., Belessiotis, V., Bergeles, G.C.
• Format: Article
• Language: English
• Subjects: Applied sciences; Design. Technologies. Operation analysis. Testing; Electronics; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Flow contraction; Heat transfer; Horseshoe vortex; Integrated circuits; Plate–fin heat sink; Secondary flow pattern; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Stepwise-varying width; Theoretical studies. Data and constants. Metering
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/j.ijthermalsci.2012.12.016

A numerical investigation based on the finite volume methodology of the three-dimensional laminar flow and conjugate heat transfer inside a plate–fin heat sink with stepwise-varying channel width is presented. Results are obtained for the three-dimensional flow developed in the vicinity of the flow contraction as manifested by the existence of two pairs of contra-rotating longitudinal vortices, one at the corners of the fin leading edge and the other at the flow separated regions. The topology of the flow is thoroughly examined and the contributions of the endwalls and the front surface of the flow-contracting fin to the mechanisms that cause the emergence of the three-dimensionality are determined. It is established that the corner longitudinal vortices are in fact horseshoe vortices, which emerge due to the deceleration effect of the fin front surface on the oncoming fluid. Furthermore, the interaction between the corner longitudinal vortices and the downstream recirculation bubble formed over the fin tip is also elucidated. The analysis covers a wide range of flow conditions within the laminar region in order to monitor the effect of the Reynolds number on the flow topology and to verify that the flow remains symmetrical in this region. From the numerical results, it is deduced that the recirculation downstream of the flow contraction has a beneficial impact on the heat sink thermal performance, a fact quantified through the local Nusselt number distributions. [Display omitted] ► Laminar forced convection inside variable-width heat sink is numerically investigated. ► The topology of the contraction-induced 3-D recirculation pattern is characterized. ► Onset of two pairs of longitudinal vortices due to the contraction effect found. ► Pattern of overlapping cold and warm fluid layers formed downstream of the contraction. ► Heat transfer significantly enhanced in comparison to parallel channel flow.