Computation of flow and heat transfer through channels with periodic dimple/protrusion walls using low-Reynolds number turbulence models

Abstract

Purpose This paper aims to predict turbulent flow and heat transfer through different channels with periodic dimple/protrusion walls. More specifically, the performance of various low-Re k-ε turbulence models in prediction of local heat transfer coefficient is evaluated. Design/methodology/approach Three low-Re number k-ε turbulence models (the zonal k-ε, the linear k-ε and the nonlinear k-ε) are used. Computations are performed for three geometries, namely, a channel with a single dimpled wall, a channel with double dimpled walls and a channel with a single dimple/protrusion wall. The predictions are obtained using an in house finite volume code. Findings The numerical predictions indicate that the nonlinear k-ε model predicts a larger recirculation bubble inside the dimple with stronger impingement and upwash flow than the zonal and linear k-ε models. The heat transfer results show that the zonal k-ε model returns weak thermal predictions in all test cases in comparison to other turbulence models. Use of the linear k-ε model leads to improvement in heat transfer predictions inside the dimples and their back rim. However, the most accurate thermal predictions are obtained via the nonlinear k-ε model. As expected, the replacement of the algebraic length-scale correction term with the differential version improves the heat transfer predictions of both linear and nonlinear k-ε models. Originality/value The most reliable turbulence model of the current study (i.e. nonlinear k-ε model) may be used for design and optimization of various thermal systems using dimples for heat transfer enhancement (e.g. heat exchangers and internal cooling system of gas turbine blades).

An extended and improved particle‐spectral method for analysis of unsteady inviscid incompressible flows through a channel of finite length

“…We use two manners to approximate the vorticity field. First, in our approach, particles are markers with vorticity values defined by conditions (7) or (4). We use particles with both nonzero and zero vorticity.…”

“…This interest is because of the relevance of these problem formulations to many real‐world problems. For example, the problems of blowing ventilation of rooms and tunnels, 1 transport and control of environmental pollution in fluid, 2 flows in pipes, 3,4 vocal tract modeling 5 and other problems can describe as flows of inviscid fluid in channels. To understands many hydrodynamic processes in complex channels allows analytical and numerical analysis of inviscid incompressible fluid flows mathematical models 6‐9 …”

Numerical analysis of heat transfer characteristics in a pin fin-dimpled channel with different pin fins and dimple locations

“…The cooling air pumped into the turbine blade internal passage is used to carry off the heat from the hot wall. Many turbulence promoters, rib (Li et al , 2015; Raisee and Rokhzadi, 2009; Singh et al , 2017; Xie et al , 2015), pin fin (Du et al , 2021; Luo et al , 2020; Ye et al , 2019), dimple (Fazli and Raisee, 2019; Rao et al , 2015; Vinze et al , 2019), etc., are arranged on the internal passage wall so as to low the thermal load by promoting the convective heat transfer between the hot wall and cooling air. The turbine blade trailing edge is always arranged with pin-fin arrays to enhance heat transfer.…”

Influence of Dimple Height on Turbulent Heat Transfer of Fin Array with Alternate Convex/Concave Dimples

“…The friction factor value of the fin with dimples as well as protrusions on the opposite surface was higher than that of the one with dimples and no dimpled surface on the opposed wall. Fazli and Raisee [8] evaluated the heat transfer coefficient of various ducts with repeated dimple/protrusion surfaces under turbulent flow. They found that using the nonlinear k-ε model attained a greater recirculation zone within the dimple via larger impact and upward flow than the linear k-ε model as well as the zonal k-ε model.…”