CFD Study of Effects of Module Geometry on Forced Convection in a Channel with Non‐Conducting Fins and Flow Pulsation

Abstract

CFD simulations were carried out to investigate the effects of the module geometry on forced convection in a rectangular channel containing series of regularly spaced non-conducting baffles with flow oscillation. The simulations were performed at constant wall temperature. Steady-flow Reynolds numbers Re in the range of 200 and 600 were studied. The results of the CFD simulations show that, for the effect fin spacing to be significant on heat transfer enhancement in finned system with oscillating flow, the oscillating flow velocity must be higher than the mean flow velocity. Superposition of oscillation yields increasing heat transfer performance with increasing fin height. Fin geometry with pyramidal shape yields highest performance in terms of the heat transfer effectiveness. IntroductionIn order to generate very complex transient interactions of eddies and flow deflection especially in the laminar flow regime, pulsation of flow through a duct containing series of transverse sharp edges can be used. According to Ni and Gough [1], the fluid mechanical conditions of this system were described to be complex, with similar magnitudes for both axial and radial velocity components. This has been found to yield significant influences on both heat and mass transfer. The fluid mechanical conditions for this kind of system were described to be governed by three main dimensionless groups, i.e. the oscillatory Reynolds number Re osc , the steady Reynolds number Re and the Strouhal number St [1][2][3][4][5][6][7]. The oscillatory Reynolds number describes the intensity of mixing applied to the system and the Strouhal number is the ratio of the system diameter to the stroke length (amplitude), which is a measure of the effective eddy propagation [6,7]. In [4][5][6], the dimensionless amplitude, which is the ratio of the oscillation amplitude to the hydraulic diameter of their device, was used instead of the Strouhal number. In addition, non-dimensional geometric parameters were also considered in the dimensionless groups, for the description of fluid mechanical conditions of the system in [4][5][6].Several research efforts have been made to develop the basics for the increased transport in this system. In [6,[8][9][10][11], the effects of flow pulsation in a channel or duct containing sharp edges arranged in ducts on the heat transfer coefficient were considered. A numerical study of the laminar natural convection from a vertical plate with non-conducting baffles subjected to a periodic oscillation was performed in [10]. Local heat transfer measurements for oscillatory flow in a channel with a single conducting baffle was considered in [11]. A numerical study of the effects of a horizontal baffle on the heat transfer characteristics of pulsating mixed convection in a parallel vertical open channel was studied in [9]. The heat transfer performance of a periodically baffled tube subjected to oscillatory flow was investigated experimentally in [2,3,8]. The baffles were conducting and rectangular in shape. The influence of serie...

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