The interaction effects of surface radiation with turbulent natural convection of a transparent medium in rectangular enclosures have been numerically analyzed, covering a wide range of Rayleigh number from 10 9 to 10 12 and aspect ratio from 1 to 200. The vertical walls of the enclosure are isothermal and maintained at different temperatures. The adiabatic top and bottom walls of the enclosure have been modelled for the limiting cases of negligible or perfect conduction along their lengths. The interaction with surface radiation results in larger velocity magnitudes and turbulence levels in the vertical as well as horizontal boundary layers, leading to an increase in the convective heat transfer by ∼25 percent. Due to the asymmetrical coupling of radiation, the augmentation of convective Nusselt number of the cold wall is larger than that of the hot wall. In tall enclosures, the convective Nusselt number exhibits three distinct regimes with respect to aspect ratio, viz. the slow growth regime, the accelerated growth regime and the invariant (or saturated) regime

Interaction Effects Between Surface Radiation and Turbulent Natural Convection in Square and Rectangular Enclosures

Nusselt number for the natural convection and surface thermal radiation in a square tilted open cavity

Conjugate heat transfer by natural convection, conduction and radiation in open cavities

The radiation effect of gray surfaces on multiple steady-state solutions obtained in a square enclosure filled with air has been investigated numerically, by a finite-difference procedure. The bottom and top surfaces of the cavity are, respectively, heated and cooled at constant temperatures, while its vertical walls are adiabatic. Parameters of the problem are the Rayleigh number ( ) and the surface emissivity ( ). The results obtained show that surface radiation alters significantly the existence range of the solution and the average heat transfer through the horizontal walls of the cavity. The parameter is found to reduce considerably the critical Rayleigh number characterizing the transition toward the oscillatory convection.

Interaction between natural convection and radiation in a square cavity heated from below

Conjugate natural convection combined with surface thermal radiation in a three-dimensional enclosure with a heat source

The interaction of natural convection with thermal radiation of gray surfaces in a square enclosure filled with air has been numerically investigated. The effect of radiation on the flow field, temperature distribution, and heat transfer is predicted. The result shows that surface radiation significantly altered the temperature distribution and the flow patterns, especially at higher Rayleigh numbers. The average convection Nusselt number increases with the increase of Ra. The presence of surface radiation can change the value of average convection Nusselt number, but only little variation can be observed with the increase of emissivity. The average radiative Nusselt number rises quickly with the increase of emissivity, and radiation heat transfer plays an important part in overall heat flux at larger emissivity. The correlation of entire average Nusselt number has also been discussed for evaluating heat transfer through the enclosure,

M. Akiyama

Papers

Numerical analysis of natural convection with surface radiation in a square enclosure