Radiation Effects on Turbulent Mixed Convection in an Asymmetrically Heated Vertical Channel

ABSTRACT

The purpose of present study is to numerically investigate the radiation effects on turbulent mixed convection flow between two differentially heated vertical parallel plates. Two flow situations known as aiding and opposing flow are considered. Frictional Reynolds number and Grashof number are assumed to be 150 and 1.6 × 10⁶, respectively. Both hydrodynamically and thermally developing and fully developed regions in the channel are investigated. Three Reynolds-averaged Navier–Stokes-based low Reynolds turbulence models are evaluated and the model with better overall performance is applied to the simulations. The radiative transfer equation for the gray and participating fluid is solved using the discrete-ordinates method, adopting its eighth-order quadrature scheme. The effects of two radiative parameters, namely, wall emissivity and optical thickness, on the flow and thermal fields, Nusselt number, and friction factor are addressed. Present results indicate that the presence of thermal radiation has a significant influence on flow and thermal fields. With an increase in wall emissivity and optical thickness, influence of radiation on the mean velocity, mean temperature, and turbulence kinetic energy profiles grows in both aiding and opposing regions. This results in an increase in bulk temperature, centerline velocity, and Nusselt number and a decrease in friction factor on both sides.

Additional information

Notes on contributors

Farzad Bazdidi-Tehrani

Farzad Bazdidi-Tehrani completed his M.S. and Ph.D. degrees at Leeds University, UK. He joined the School of Mechanical Engineering at Iran University of Science and Technology (IUST) in 1991, and since then has been active in both teaching and research. He has taught several courses at both undergraduate and graduate levels. His current research fields of interest include modeling of cooling techniques related to hot sections in gas turbine engines and electronic components, combined heat transfer (mixed convection–radiation) in channels, turbulent reactive and nonreactive flows, and nano convection heat transfer.

Masoud Aghaamini

Masoud Aghaamini obtained his B.S. degree from the University of Kashan, and has completed his M.S. degree in energy conversion at the School of Mechanical Engineering, Iran University of Science and Technology, with distinction. His field of research includes turbulence modeling and various heat transfer phenomena such as thermal radiation, and forced, free, and mixed convection in vertical and horizontal channels. He is planning to continue his studies at Ph.D. level.

Saied Moghaddam

Saied Moghaddam received his B.S. and M.S. degrees in the field of energy conversion at the Department of Mechanical Engineering, University of Tehran. He is currently a Ph.D. candidate in the Combined Heat Transfer research group of Iran University of Science and Technology. His current research field is focused on turbulence using LES and RANS techniques and various heat transfer phenomena such as thermal radiation and forced, free, and mixed convection in various configurations. Also, turbulence-radiation interaction and non-Boussinesq conditions are two of his main studies.