Full Length Research Paper

Numerical study of laminar mixed convection heat transfer of power-law non-Newtonian fluids in square enclosures by finite volume method

Mohammad Reza Safaei¹*, Behnam Rahmanian² and Marjan Goodarzi³

¹Young Researchers Club and Department of Mechanical Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran.

²Department of Mechanical Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran.

³Department of Computer Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran.

*Corresponding author. E-mail: CFD_Safaiy@yahoo.com.  Tel: +98 9151022063.
 

Accepted 23 October, 2011.

Abstract

In this study, we have numerically considered mixed convection heat transfer in a square enclosure with cold left and right walls, insulated moving upper wall and hot fixed lower wall. The governing flows of two reliable articles were initially modeled and after validating calculations, the given flow of the study was solved by finite volume method. To examine the effects of different factors, such as Prandtl, Reynolds and Rayleigh numbers on heat transfer in a square enclosure, the laminar flow of Newtonian fluids was approximated and then laminar flow of non-Newtonian fluids, such as carboxy methyl cellulose (CMC) and carboxy poly methylene (Carbopol) water solutions were studied for different Richardson numbers. It was found from the results obtained in the present study that when Ri is less than 1, governing heat transfer inside the enclosure is forced convection for non-Newtonian fluids similar to Newtonian ones. When Ri increases, the effect of forced convection is reduced and natural convection heat transfer increases. It was also found that in constant Grashof numbers, if n decreases, the dimensionless temperature increases. Also, if n is constant, any increase in Grashof number causes a higher dimensionless temperature. It may be related to the fact that in similar conditions, any increase in forced convection, makes shear stresses more.

Key words: Richardson number, power-law non-Newtonian fluids, mixed convection heat transfer, square enclosure, finite volume method.