This paper deals with numerical investigation of a natural convective flow in a horizontal annular space between a heated square inner cylinder and a cold elliptical outer cylinder with a Newtonian fluid. Uniform temperatures are imposed along walls of the enclosure. The governing equations of the problem were solved numerically by the commercial code Fluent, based on the finite volume method and the Boussinesq approximation. The effects of Geometry Ratio GR and Rayleigh numbers on fluid flow and heat transfer performance are investigated. The Rayleigh number is varied from 103 to 106. Throughout the study the relevant results are presented in terms of isotherms, and streamlines. From the results, we found that the increase in the Geometry Ratio B leads to an increase of the heat transfer coefficient. The heat transfer rate in the annulus is translated in terms of the average Nusselt numbers along the enclosure’s sides. Tecplot 7 program was used to plot the curves which cleared these relations and isotherms and streamlines which illustrate the behavior of air through the channel and its variation with other parameters. The results for the streamlines, isotherms, local and average Nusselt numbers average Nusselt numbers are compared with previous works and show good agreement.

The second part study of this paper is to numerically study the double-diffusive natural convection phenomenon inside a space annulus, situated between two horizontal confocal elliptic cylinders filled with a laminar flow, is presented. The elliptical coordinates do utilize to transform the physical domain into one rectangular. The basic equations are discretized using the finite-volume method. Using a developed code, the study covers a wide range for (103 ≤ Rat ≤105), Le = 2, N = 1, e = 0.52, 0.62, 0.72, 0.82.We have made some detailed studies covering the influence of the internal eccentricity parameter e1 on heat and mass transfer. Results do present in the form of isotherms, streamlines, and heat transfer. The local and average numbers for Sherwood and Nesselt are also displayed.Comparison with the published results showed that there is a good agreement. Keywords:double-diffusive, natural convection, elliptic cylinders, Rayleigh number, Lewis number.

The development of modern technology in microelectronics and power engineering requires the creation of efficient cooling systems. This is made possible by the use of special fin technology inside the cavity or special heat transfer Ethylene glycol-copper nanofluids to intensify the heat removal from the heat-generating elements. A numerical study of the natural convection of stationary laminar heat transfers in a closed rectangular cavity with a local source of internal volumetric heat generation. For different Rayleigh numbers and different volume fractions of nanoparticles. The system of equations governing the problem was solved numerically by the fluent computer code based on the method of finite volumes. Based on the Boussinesq approximation. Interior and exterior surfaces are maintained at a constant temperature. The study is carried out for Rayleigh numbers ranging from 104 to 106. The effects of different Rayleigh numbers and volume fractions of nanoparticles on natural convection have been studied. The results are presented as isotherms, isocurrents, and local and mean Nusselt numbers. The aim of this study is to see the influence of the thermal Rayleigh number and the volume fraction of the nanoparticles on the rate of heat transfer.

In this paper a numerical study of natural convection of stationary laminar heat transfers in a horizontal ring between a heated square inner cylinder and a cold elliptical outer cylinder is presented. A Cu-water nanofluid flows through this annular space. Different values of the Rayleigh number and volume fraction of nanoparticles are studied. The system of equations governing the problem was solved numerically by the fluent calculation code based on the finite volume method and on the Boussinesq approximation. The interior and exterior surfaces are kept at constant temperature. The study is carried out for Rayleigh numbers ranging from 103 to 105 . We have studied the effects of different Rayleigh numbers and volume fraction of nanoparticles on natural convection. The results are presented as isotherms, isocurrents, and local and mean Nusselt numbers. The aim of this study is to study the influence of the thermal Rayleigh number and volume fraction of nanoparticles on the heat transfer rate.

In this document, a numerical study of the natural convection of steady-state laminar heat transfer in a horizontal ring between a heated hexagonal inner cylinder and a cold hexagonal outer cylinder. A Cu - water nanofluid traverses this annular space. The system of equations governing the problem was solved numerically by the fluent calculation code based on the finite volume method. Based on the Boussinesq approximation. The interior and exterior sides from the two cylinders are maintained at a fixed temperature. We investigated the impacts of various thermal Rayleigh numbers (103≤ Rat ≤2.5x105), and the volume fraction from the nanoparticles (0≤ Ø ≤0.12) on fluid flow and heat transfer performance. It is found that in high thermal Rayleigh numbers, a thin thermal boundary layer is illustrated at the flow that heavily strikes the ceiling and lower from the outer cylinder. In addition, the local and mean Nusselt number from a nanofluid are enhanced by enhancing the volume fraction of the nanoparticles.The results are shown within the figure of isocurrents, isotherms, and mean and local Nusselt numbers. Detailed results of the numerical has been compared with literature ones, and it gives a reliable agreement.