Numerical and experimental study of natural convection heat transfer on flat and corrugated plates

Abstract

Purpose The purpose of this study is to numerically and experimentally investigate the natural convection heat transfer in flat plates and plates with square, trapezoidal and triangular corrugations. Design/methodology/approach This work is an extension of the previous studies by Verderio et al. (2021a, 2021b, 2021c, 2021d, 2022a). An experimental apparatus was built to measure the plates’ temperatures during the natural convection cooling process. Several physical parameters were evaluated through the experimental methodology. Free and open-source computational tools were used to simulate the experimental conditions and to quantitatively and qualitatively evaluate the thermal plume characteristics over the plates. Findings The numerical results were experimentally validated with reasonable accuracy in the range of studied RaLP for the different plates. Empirical correlations of Nu¯LPexp=f(RaLP), h¯conv=f(RaLP) and Nu¯LPexp⋅(A/AP)=f(RaLP), with good accuracy and statistical representativeness, were obtained for the studied geometries. The convective thermal efficiency of corrugated plates (Δη), as a function of RaLP, was also experimentally studied quantitatively. In agreement with the findings of Oosthuizen and Garrett (2001), the experimental and numerical results proved that the increase in the heat exchange area of the corrugations has a greater influence on the convective exchange and the thermal efficiency than the disturbances caused in the flow (which reduce h¯conv). The plate with trapezoidal corrugations presented the highest convective thermal efficiency, followed by the plates with square and triangular corrugations. It was also proved that the thermal efficiency of corrugated plates increases with RaLP. Practical implications The results demonstrate that corrugated surfaces have greater thermal efficiency than flat plates in heating and/or cooling systems by natural convection. This way, corrugated plates can reduce the dependence on auxiliary forced convection systems, with application in technological areas and Industry 4.0. Originality/value The empirical correlations obtained for the corrected Nusselt number and thermal efficiency for the corrugated plate geometries studied are original and unpublished, as well as the experimental validation of the developed three-dimensional numerical code.

Numerical investigation of three-dimensional natural convection heat transfer on corrugated plates of variable height

“…The plate with triangular corrugations with r = 1.50 presented the best results in terms of total heat transfer rate, followed by the plate with trapezoidal corrugations and the plate with rectangular corrugations. This order differs from the results of Verderio Junior et al (2023), showing that the analysis of this type of surface, especially in conditions of changes in the geometry of the plates, requires in-depth studies that consider the combined effects of the flow disturbances and the increased surface area for convective heat transfer.…”

“…The range of simulated Rayleigh numbers in the present work is identical to that considered in (Verderio Junior et al , 2023). All other aspects of the numerical-computational methodology used in this work are reported in detail in the previous study by Verderio Junior et al (2023).…”

“…This work is an extension and finalization of the studies developed by Verderio Junior et al (2021a); Verderio Junior et al (2021b); Verderio Junior et al (2021c); Verderio Junior et al (2021d); Verderio Junior et al (2022a); Verderio Junior et al (2023). Its main objective, in contrast to previous references on the subject that only considered corrugations of uniform height and using OpenFOAM® and other free and open-source numerical-computational tools, is to numerically study the influence of different corrugation profiles (rectangular, trapezoidal and triangular) of varying heights on the natural convection heat transfer process over isothermal plates.…”

“…That are: It should be noted that A is the natural convection heat transfer area of the new corrugated plate geometry (with height variations in the corrugations) and A ref is the natural convection heat transfer area of the reference corrugated plate geometry (with corrugations of the same shape but without height variations); see Table A1. The average convective heat flux over the plates, q″true¯, is calculated using the wallHeatFluxIncompressible function of OpenFOAM® during the post-processing stage of the simulations, and the term Δηconv*, in percentage, is the convective thermal efficiency gain of the reference geometries in comparison with flat plates, available in the previous study by Verderio Junior et al (2023).…”

“…In this way, from the existing technological demand and with a direct focus on everyday industrial applications of thermal dissipation systems – exploring the mathematical-physical-numerical and experimental aspects of the phenomenon of natural convection on flat and corrugated plates – the studies by Silva et al (2021); Verderio Junior et al (2021a); Verderio Junior et al (2021b); Verderio Junior et al (2021c); Verderio Junior et al (2021d); Verderio Junior et al (2022a); Verderio Junior et al (2023) are highlights. These researches, following a worldwide trend of producing science at low cost, were developed with the exclusive use of free and open-source software.…”