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

Abstract

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 109 to 1012 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. The augmentation of convective Nusselt number for perfectly conducting horizontal walls is found to be of similar nature to that in the case with radiation interaction.

Conjugate turbulent natural convection in the roof enclosure of a heavy construction building during winter

“…The mean Nusselt number Nu m calculated using the turbulent model was compared with those reported in Refs. [25][26][27][28][29]. The comparison revealed better agreement of the model results with the experimental data than the others as shown in Table 2.…”

“…The computational results are compared to the experimental data in Table 2. The table also presents numerical results by Dixit and Babu [26], Le Que're [27], Velusamy et al [28], Henkes [29] for the same benchmark case. The mean Nusselt number Nu m calculated using the turbulent model was compared with those reported in Refs.…”

“…Present study Dixit and Babu [26] Le Que're [27] Velusamy et al [28] Henkes [29] Elsherbiny et al [ vertical velocity and temperature profiles at X 2 = 0.5 (i.e., horizontal median plane) were compared as shown in Fig. 2.…”

“…Both dimensionless Table 2 Comparison of predicted average Nusselt number Nu m on the hot vertical wall of the enclosure with Refs. [25][26][27][28][29] …”

Heat Transfer and Air Flow in a Domestic Refrigerator

“…Several authors [31][32][33][34] showed by experimental and numerical approaches that these two heat transfer modes occur simultaneously. Ramesh and Venkateshan 32 showed experimentally that for a square enclosure (vertical walls maintained at 35 and 65°C, adiabatic horizontal walls, Ra = 5 × 10 5 ), the heat transfer by convection and radiation between high emissive vertical walls (ε = 0.85) is twice of that of polished ones (ε = 0.05).…”