Publications
Laminar free convection heat transfer between vertical isothermal plates
Nov 12, 2016Journal Journal of Engineering Thermophysics
Publisher © Pleiades Publishing, Ltd. springer nature
DOI https://doi.org/10.1134/S1810232816040081
Volume 25
The paper represents results on numerical investigation of flow and heat transfer between two isothermal vertical plates under laminar natural convection. A system of complete Navier–Stokes equations is solved for a two-dimensional gas flow between the plates along with additional rectangular regions (connected to inlet and outlet sections), whose characteristic sizes are much greater than the spacing between the plates. The calculations were performed over very wide ranges of Rayleigh number Ra = 10 ÷ 105 and a relative channel length AR = L/w = 1 ÷ 500. The influence of the input parameters on the gas-dynamic and thermal structure of thermogravitational convection, the local and mean heat transfer, and also the gas flow rate between the plates (convective draft. We determined sizes of the regions and regime parameters when the local heat flux on the walls tends to zero due to the gas temperature approach to the surface temperature. It is shown that the mean heat transfer decreases as the relative channel length AR grows, whereas the integral gas flow rate (convective draft) and Reynolds number in the channel Re = 2wUm/ν increase. The use of a modified Rayleigh number Ra* = Ra · (w/L) (Elenbaas number) leads to generalization of calculation data on mean heat transfer. These data are in good agreement with the correlations for heat transfer [1, 2] and gas flow rate [3]. The reasons of variation of the data in the range of low Rayleigh numbers are discussed in detail.
Expermintal And Theoretical Study Of Natural Convection Heat Transfer Between Two Concentric Cylinders Filled With Porous Medium
Dec 28, 2009Journal Al-Rafidain Engineering Journal
Publisher College of Engineering, University of Mosul, IRAQ
DOI https://doi.org/10.33899/rengj.2009.43639
Issue 6
Volume 17
Abstract Porous media have considerable importance in improvement of heat transfer and storage. This research includes an experimental and theoretical study of natural convection heat transfer between two concentric cylinders filled with a porous medium, under condition of applying uniform heat flux on the inner cylinder and constant outer surface temperature for the outer cylinder. Two types of filling material were used as porous medium , iron and glass beads , the study shows that the heat dissipated ability in the inner cylinder is function of Rayligh number , and the Nusselt number increase is directly proportional with the increase in Rayligh number . Fluent program was used to show the heat dissipation and the flow lines inside the gap between the two cylinders , the experimental results show that the nature of the heat distribution depends greatly on Rayligh number , and the use of highly heat conductive materials as porous medium will completely cancel the convection as a mean of heat transfer. Key wards: Heat transfer, Natural convection, Porous medium, and two concentric cylinders.