Comparison of Natural Convection around a Circular Cylinder with a Square Cylinder Inside a Square Enclosure

Abstract

Nu merical calcu lations are carried out for natural convection induced by a temperature difference between a cold outer square enclosure and a hot inner cy linder with two different geo metries (i.e. circular and square). A two-dimensional solution for natural convection is obtained, using the finite volu me method for different Rayleigh nu mbers varying over the range of (10 3 -10 5 ). The study goes further to investigate the effect of vertical position of the inner cylinder on the heat transfer and flow field. The location of the inner cylinder is vertically changed along the center-line of the square enclosure. The number, size and form of the vortices strongly depend on the Rayleigh nu mber and the position of the inner cylinder. The results show that for both cylinders, at low Rayleigh numbers of 10 3 and 10 4 , the bifurcation fro m the bicellular vortices to an uni-cellular vortex occurs when an inner cylinder is placed at a certain distance from the center of the enclosure. When Ra = 10 5 , only a uni-cellu lar vortex is formed in the enclosure irrespective of the position of the inner cylinder. A lso as the obtained total surfaces-averaged Nusselt numbers of the enclosure show, in all cases, at the same Rayleigh number, the rate of heat transfer fro m the enclosure which the circular cylinder is located inside is better.

Optimization of Convective Heat Transfer from Two Heating Generators into Horizontal Enclosure Including A Discrete Obstacle: A Lattice Boltzmann Comprehensive Investigation

“…For higher length of the obstacle corresponding to LO = 0.4, isotherms and streamlines show a weaker interaction between thermals plumes separated by the obstacle. For this configuration (LO = 0.4), it can be concluded that the behavior of the flow in each region between the obstacle and the cold wall of the enclosure is comparable to that of natural convection in a rectangular confined medium heated from below and symmetrically cooled from sides (Roychowdhury D. G. et al (2002), Goutam S. et al (2007), Paroncini M. et al (2009, Khozeymehnezhad H. et al (2012)).…”

Natural Convection Heat Transfer Inside Horizontal Circular Enclosure With Triangular Cylinder at Different Angles of Inclination

“…Buoyancy effects around a circular enclosure contains concentrically heated triangular cylinder has considerable attention by many researchers due to its important practical engineering applications, such as the solar collectors, nuclear reactor applications, cooling of electronic devices, etc [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The outer surface of the enclosure is to reduce the heat transfer from the inner hot surface or to protect the inner body in harsh outdoor environment.…”

“…They found that the average heat transfer rate increases with increasing of Rayleigh numbers and nanoparticle volume fraction. Khozeymehnezhad and Mirbozorgi, [9] made a comparison of natural convection around a hot circular cylinder with a hot square cylinder with different locations inside a cooled square enclosure. They showed that the rate of heat transfer from the enclosure which the circular cylinder is located inside is better than square cylinder at the same Rayleigh number.…”

Natural Convection Around a Heat Conducting and Generating Solid Body Inside a Square Enclosure With Different Thermal Boundaries

“…In numerous investigations [3][4][5][6][7][8][9], an enclosure include obstacles of different geometries (fin, baffle, plate and square or circular body) has been studied by many authors. The main interest in heat transfer is, a heated body should be cooled (For example, electrical chip) or should heat the environment (For example, radiators inside building).…”

“…They compared the results of conducting body with adiabatic and neutral isothermic bodies. Khozeymehnez and Mirbozorigi [9] compared the results of natural convection around a circular cylinder with a square cylinder inside a square enclosure.…”