Experiments on mixed convection in a vented differentially side-heated cavity filled with a coarse porous medium

Experiments on mixed convection in a vented differentially side-heated cavity filled with a coarse porous medium

Ataei Dadavi, I. (TU Delft ChemE/Transport Phenomena)
Chakkingal, M. (TU Delft ChemE/Transport Phenomena)
Kenjeres, S. (TU Delft ChemE/Transport Phenomena)
Kleijn, C.R. (TU Delft ChemE/Transport Phenomena)
Tummers, M.J. (TU Delft Fluid Mechanics)

2020

This paper reports on an experimental study of mixed convection flow and heat transfer in a vented, differentially side-heated cubical cavity filled with a porous medium consisting of relatively large solid low-conductivity spheres. Rayleigh numbers and Reynolds numbers are varied over the ranges 6 × 10⁶ < Ra < 7 × 10⁷ and 240 < Re < 4250, respectively, for a fixed Prandtl number of Pr = 6.75, thus covering more than three decades in Richardson numbers Ri = Ra/(Re² Pr). Heat transfer measurements were combined with measurements of the velocity field (using particle image velocimetry) and the temperature field (using liquid crystal thermography) to better understand the dependence of the Nusselt number, Nu, on the Richardson number. We observed three different flow and heat transfer regimes depending on the Richardson number. For Ri < 10, the flow structure and the Nusselt number scaling are similar to those for the pure forced convection, i.e., the Nusselt number scales as Nu ~ Re^0.61 independent of Rayleigh number. For Ri > 40, natural convection dominates the flow in the vicinity of the heating wall. The Nusselt number becomes less sensitive to the Reynolds number and is mainly determined by the Rayleigh number. In the intermediate regime for 10 < Ri < 40, the upward directed natural convection flow at the heating wall competes with the downward directed forced flow leading to a minimum effective Nusselt number. A Nusselt number correlation is derived that is valid in the range 0.1 < Ri < 100 covering all three regimes.

Heat transfer
Mixed convection
Packed beds
Porous media
Refractive index matching
Vented cavity

http://resolver.tudelft.nl/uuid:9e447ca4-f102-4998-9928-c9286a454146

https://doi.org/10.1016/j.ijheatmasstransfer.2019.119238

0017-9310

International Journal of Heat and Mass Transfer, 149

Institutional Repository

journal article

© 2020 I. Ataei Dadavi, M. Chakkingal, S. Kenjeres, C.R. Kleijn, M.J. Tummers