Browsing by Author "Gokaslan, Mustafa Yasin"

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Experimental Investigation of Pressure Drop and Heat Transfer in Porous Media Based on 3d Printed Triple Periodic Minimum Surfaces
(Taylor & Francis inc, 2025) Gokaslan, Mustafa Yasin; Yildiz, Erdem
Porous media are widely preferred for heat transfer applications because of complex structure and high porosity. It is relatively easy to produce complex structures with the additive manufacturing method. In this study, Gyroid-based triple periodic minimal surface is produced ABS (Acrylonitrile butadiene styrene) and PLA (polylactic acid) materials using 3D printers. The pressure drops and heat transfer in the porous structure with the gyroid model are investigated experimentally. Permeability and Forchheimer coefficients are determined for each gyroid porous channel. While the permeability and Forchheimer coefficient of the porous medium of PLA were calculated as 2.97 x 10-8 m2 and 0.07, respectively, the permeability and Forchheimer coefficient of the porous medium of ABS were calculated as 5.52 x 10-8 m2 and 0.09. The correlation between the Reynolds number and pressure drop per length is given. The gyroid structure-filled channel is heated by an asymmetric heat flux on the bottom side. The convection heat transfer in polymer-based porous media was investigated. Also, the correlation between the Nusselt number and the Reynolds number based on permeability is presented. While the Nusselt correlation of the PLA porous medium was obtained as $N{u_K} = 0.08Re_K<^>{0.57}$NuK=0.08ReK0.57, the Nusselt correlation of the ABS porous medium was found to be $N{u_K} = 0.09Re_K<^>{0.61}$NuK=0.09ReK0.61. There are improvements in heat transfer due to the flow mixing effect of the porous medium. The study aims to broaden the current knowledge of heat transfer in polymer porous structures. Especially, this study investigates heat transfer and flow in polymer-based porous structures with a low thermal conductivity coefficient produced by 3D printers.
Experimental Study on Laminar Air Flow and Heat Transfer Through a Spiral Channel Filled With Steel Balls
(Elsevier France-editions Scientifiques Medicales Elsevier, 2022) Gokaslan, Mustafa Yasin; Ozdemir, Mustafa; Kuddusi, Lutfullah
The demand in the industry for high heat transfer performance is increasing. Studies have been greatly carried out on the new emerging technologies and creating new arrangements in engineering design. Porous media or curved channel increases heat transfer. Studies have been carried out for many years in heat transfer in curved channels and porous media separately. However, in this study, the heat transfer in the case of both curved and porous media is investigated experimentally. The experiments are conducted at constant heat flux in laminar airflow regime. A total of 169 sets of experiments are carried out in 8 experimental groups, in two different radii of curvature, in the unfilled spiral channel and in spiral packed bed formed by locating 3 different ball diameters (2.00, 2.38 and 3.17 mm). Nusselt number (Nu) correlations are presented separately for both the inner surface, the outer surface and taking the average of the inner and outer surface temperatures in unfilled spiral channel. Nusselt numbers (Nu(i), Nu(o), Nu(a)) for inner surface, outer surface and the average of the inner and outer surface temperature are obtained as Nu(i) = 0.93De(0.45), Nu(o) = 0.50De(0.58), Nu(a) = 1.16De(0.44) respectively. Heat transfer in spiral packed beds has not been investigated or reported in the available literature. By defining a modified Dean number (De(m)) to reveal the effect of curvature in spiral packed beds, a correlation between the modified Dean number (De(m)) and the Nusselt number (Nu(p)) based on ball diameter is given. Nusselt number for spiral packed beds are presented as Nu(p) = 0.19De(m)(0.81). This correlation is also suitable for straight packed beds when the curvature ratio is neglected.
Heat Transfer in the Entrance Region of Annular Laminar Flow With Constant and Different Heat Flux on Two Walls
(Wiley-v C H verlag Gmbh, 2025) Gokaslan, Mustafa Yasin; Kuddusi, Yasemen; Kuddusi, Luetfullah
Heat transfer differs in the regions where the flow is developed and developing thermally. These regions can be differentiated by using the thermal entry length. Many researchers have presented correlations to determine the thermal entry length for natural and forced convection. In this study, heat transfer in the entrance region of a concentric annuli is investigated. It is accepted that beginning from the inlet of annuli the flow is developed hydrodynamically and it is developing thermally. Heat transfer is investigated where the internal or external surfaces of the annuli are at constant but different heat fluxes. The fluid velocity is assumed to be constant or radially variable. Due to thermal boundary conditions, one thermal boundary layer appears on the outer cylinder surface, another on the inner cylinder surface. The edge of two boundary layers will be adiabatic and naturally, the temperature of fluid between the two edges will be equal to free stream temperature. Transformation, Separation of Variables method, eigenvalue problem, Sturm-Liouville system, Bessel differential equation and properties of orthogonal functions are used in solution of the problem. Exact and analytical solutions of the momentum and energy equations are presented. Velocity and temperature distributions, local Nusselt numbers and convection heat transfer coefficients are calculated for the internal and external surfaces of annuli.