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Go to Editorial ManagerAn experimental and theoretical study of free convection heat transfer for a cylinder placed in an iron test section of dimensions (0.2x0.2x0.2 m3), the test section filled with saturated porous material glass balls (5 mm), and the air is the working fluid with Raleigh number (7692.6 ? Ra ? 17654). The circular cylinder heater (D = 0.015 m, L = 0.2 m) is heated electrically, made of Copper and located in different positions (in X & Y direction). The theoretical part includes solving the free convection heat transfer using the ANSYS program (fluent). The experimental and theoretical results showed that the surface temperature values around the cylinder perimeter when changing its position within the test section are changing as moving up and down where the effect of buoyancy force appears. The maximum difference between the upper and lower position at the experimental result is 7.22%, and the average Nusselt number increases with Raleigh number and heat flux. Also, the experimental results showed that the use of porous material significantly improves the heat transfer by 48.6%. The maximum percentage change between the experimental and theoretical results is 5.46%. Moreover, experimental correlations were achieved, and a comparison was performed between the present results with the previous studies and it gives a good agreement.
A numerical study was performed of natural laminar convective heat transfer to its concentrated triangular enclosure around a horizontal circular cylinder. The air-filled enclosure kept the inner and outer cylinders at uniform temperatures. The Boussinesq density approximation to the momentum problem and the control volume approach iteratively resolved the governing equations to explain buoyancy. CFD results show that the velocity behavior increases by increasing Ra, so the stream lines becomes more sluggish and less uniform behavior and vortices gets less circulated pattern. The rotation angle ? has significant effect on vortices, at 90o gives the higher range of velocity zones of free convection with higher range. The thermal boundary layer seems to be larger in rr=0.455 as compared with rr=0.345 and decreases by increasing ?. The larger variation of isotherms and thermal boundary layer appears at lower ? because the higher heat transfer rate occurs at higher ? and becomes maximum at 90o. Eight correlations of average Nusselt number have been deduced as a function of Rayleigh number for the taken values of aspect ratio and enclosure angles of rotation and inclination.