Analysis of turbulent heat transfer and fluid flow in channels with various ribbed internal surfaces

Abstract

This paper presents results of a numerical investigation of heat transfer and flow pattern characteristics of a channel with repeated ribs on one broad wall. Numerical computations are performed for seven ribs placed on the bottom wall of a channel for Reynolds numbers ranging from 10,000 to 30,000. The newly modified ribs (the ones with convex pointing upstream/downstream rib, wedge pointing upstream/downstream rib, concave pointing upstream/downstream rib and also concave-concave rib as well as convex-concave rib), are proposed for simulation with prospect to reduce flow separation and extend reattachment area compared to the unmodified square rib.The numerical results are reported in forms of flow structure, temperature field, turbulent kinetic energy, Nusselt number, friction factor and thermal enhancement factor. The results indicate the rib with concave-concave surfaces efficiently suppresses flow separation bubble in the corner of the rib and induces large recirculation zone over those of the others, hence giving the highest Nusselt number and friction factor. On the other hand, the one with convex-concave surface provides the lowest friction factor with moderate Nusselt number. Due to the prominent effect of its low friction factor, the rib with convex-concave surface offers the highest thermal enhancement factor of 1.19.

Effect of Boundary Conditions and Turbulence Treatment on the Simulated Performance of a Ribbed Heat Exchanger

“…However, every turbulence model presented a significant underestimation of the heat transfer in the vicinity of the ribs, which was not observed in the experiments. Similar results may be found in the work published by Eiamsa-ard et al [23] on 2D numerical domains.…”

“…The majority of numerical simulations available in the literature are based on the solution of the Reynolds-Averaged Navier-Stokes (RANS) equations, in combination with different turbulence models. Eiamsa-ard and Changcharoen [23] employed the SST k-ω model to study a channel with different rib geometries, with the aim of reducing the flow separation and extending the reattachment area with respect to the more conventional squared rib configuration. Boulemtafes-Boukadoum et al [24] compared the shear stress transport (SST) k-ω model with three other turbulence models, i.e.…”

A Comprehensive Review and Comparative Study of Various Rib Configurations Used in Rectangular Duct for Heat Transfer Enhancement

“…Fig. 6 Thermal Enhancement Factor (TEF) for different shaped ribs [6] Tanda [7] et al, conducted experimental investigation of heat transfer enhancement in a rectangular duct (having aspect ratio of 5) provided with ribs inclined at 45°angle on one and two surfaces of the duct. During the experimentation the Reynolds number was varied from 9000 to 35000, rib height to hydraulic diameter ratio (e/D) was maintained at 0.09, and rib pitch to height ratio was varied from 6.66 to 20 (in 4 steps) respectively.…”

Thermal visualization on surface with transverse perforated ribs

“…The mechanism of heat transfer enhancement is based on flow separation and reattachment. In general, flow reattachment introduces strong shear flow on the surface behind each rib, resulting in an effective disruption of the thermal boundary layer and thus the improvement of heat transfer [1][2][3][4][5][6][7][8][9][10]. However, in the case of a solid rib, a large hot spot is usually generated just downstream from the rib, leading to heat transfer deterioration around that position [11][12][13] as a result of flow separation in form of flow recirculation.…”