Abstract
A computational analysis has been conducted to investigate turbulent flow and convective thermal transfer characteristics in a two-dimensional horizontal rectangular section channel with a hot lower wall-mounted diamond-shaped baffle. The calculations are based on the finite volume method, by means of Commercial Computational Fluid Dynamics software FLUENT, standard k-epsilon turbulence model with QUICK numerical scheme, and the SIMPLE discretization algorithm has been applied. The fluid flow and heat transfer characteristics, i.e., dynamic pressure coefficient, stream function, mean, axial, and transverse velocities, turbulent viscosity, temperature field, skin friction coefficients, local and average Nusselt numbers, and thermal enhancement factor are presented for flow Reynolds numbers based on the aeraulic diameter of the computational domain ranging from 12,000 to 32,000 at constant surface temperature condition along the upper and lower walls. Effect of the diamond configuration of the insulated baffle is studied numerically and the data obtained from this same baffle model are also compared with that of the simple flat rectangular baffle under similar operating conditions. Over the range under investigation, the improvements are found to be around 3.962 and 29.820 times higher than the smooth air channel with no baffle for heat thermal transfer and skin friction factor, respectively. The maximum TEF is around 1.292 at the highest Reynolds number value, Re = 32,000.
Highlights
Convective heat transfer from surfaces has been the topic of several studies in recent year
Downstream of the diamond, the current lines are generated by the effect of flow expansion, leaving the section formed by the baffle and the top channel wall
The most important phenomenon occurring in this zone is the formation of a recirculating flow whose extent is proportional to the Reynolds number
Summary
Convective heat transfer from surfaces has been the topic of several studies in recent year. Karwa et al [4] presented the paper results of an experimental study of heat transfer and friction in rectangular ducts with baffles (solid or perforated) attached to one of the broad walls. Influences of three different baffle pitch to channel-height ratios (PR = P / H = 0.5, 1 and 2) on heat transfer and pressure drop in terms of respective Nusselt number and friction factor (or energy loss for propelling air through the channel) were examined. Du et al [9] designed a special flow layout with U-shaped tubes applied in the laboratory for testing the heat transfer performances (HTPs) of molten salt in the shell side of a shell-and-tube heat exchanger (STHE) Based on this design, the transitional convective HTPs (6142 < Re < 9125) of molten salt with higher temperature (209.41-241.49 °C) in the STHE with segmental baffles (STHE-SBs) were experimentally studied, and the corresponding heat transfer correlations were fitted. The finite volume method is adopted for modelling the problem by using the software Fluent
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