Vol. 1 (2025)

Articles

Concentration Gradient Driven Mixed Convective Flow in Rectangular Enclosure with Concentrated Top Wall

Published 2025-10-27

  • Vusala Ambethkar
    • ,
  • Rama Subba Reddy Gorla

Vusala Ambethkar
Department of Mathematics, University of Delhi, Delhi–110007, India

Rama Subba Reddy Gorla
Department of Aeronautics and Astronautics, Air Force Institute of Technology, Wright Patterson Air Force Base, Dayton, Ohio 45433, USA

Abstract

Concentration gradient driven mixed convective flow in a horizontal rectangular enclosure with concentrated top wall is studied in this work. The continuity, momentum and mass transfer equations are discretized by using the hybrid finite volume method. The innovative thought in this work is to examine the sole effect of the concentration gradient on the mass transfer between the top wall and the fluid within the horizontal rectangular enclosure. The dimensionless parameters such as the Reynolds number (Re), the Schmidt number (Sc) are appropriately chosen to calculate the Richardson numbers (Ri) for specific fluids such as ammonia gas (Sc = 0.78) and methanol liquid (Sc = 556) at low (Re = 25) and high (Re = 25000) Reynolds numbers at different mass transfer Rayleigh numbers (Ram,L) in the range of 3x105 < Ram,L) < 7x109. In accordance with these calculated Richardson numbers revealed as Ri>>1 and Ri<<1 respectively, it is found that pure and negligible free convection effects prevails between the top wall and the fluid within the horizontal rectangle. When Ri~1 mixed convection results between the top wall to these fluids within the horizontal rectangle. A novel empirical correlation for calculating the average Sherwood numbers (Sh) for specific fluids at different mass transfer Rayleigh numbers as mentioned above is suggested in this research and thereby the mass transfer from the top wall to these fluids within the horizontal rectangle is examined and validated. Since this correlation is novel in nature, the conclusions regarding the mass transfer from the top wall to these fluids within the horizontal rectangle justified and comparison or improvement over the existing correlations is unnecessary. It is found that for all the boundary values of the mass transfer Rayleigh number, there is a substantial increase in the average Sherwood numbers Sh and hence the mass transfer from the top wall to the fluid (ammonia gas or methanol liquid) substantially increases within the horizontal rectangle.

Keywords

Horizontal rectangular enclosure, hybrid finite volume method, empirical correlation, Reynolds number, Rayleigh number, mass transfer, average Sherwood number

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