WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 5Citation - Scopus: 5Visualization of Heat Flow in a Vertical Channel With Fully Developed Mixed Convection(Elsevier Ltd., 2012) Çelik, Hasan; Mobedi, MoghtadaA study on visualization of heat flow in three channels with laminar fully developed mixed convection heat transfer is performed. The first channel is filled with completely pure fluid; the second one is completely filled with fluid saturated porous medium. A porous layer exists in the half of the third channel while another half is filled with pure fluid. The velocity, temperature and heat transport fields are obtained both by using analytical and numerical methods. Analytical expression for heat transport field is obtained and presented. The heatline patterns are plotted for different values of Gr/Re, thermal conductivity ratio, Peclet and Darcy numbers. It is found that the path of heat flow in the channel strongly depends on Peclet number. For low Peclet numbers (i.e., Pe = 0.01), the path of heat flow is independent of Gr/Re and Darcy numbers. However, for high Peclet numbers (i.e., Pe = 5), the ratio of Gr/Re, Darcy number and thermal conductivity ratio influence heatline patterns, considerably. For the channels with high Peclet number (i.e., Pe = 5), a downward heat flow is observed when a reverse flow exits. © 2012 Elsevier Ltd.Article Citation - WoS: 91Citation - Scopus: 108A Heatline Analysis of Natural Convection in a Square Inclined Enclosure Filled With a Cuo Nanofluid Under Non-Uniform Wall Heating Condition(Elsevier Ltd., 2012) Öztop, Hakan Fehmi; Mobedi, Moghtada; Abu-Nada, Eiyad; Pop, IoanHeatline visualization technique is used to understand heat transport path in an inclined non-uniformly heated enclosure filled with water based CuO nanofluid. The cavity has square cross-section and it is non-uniformly heated from a wall and cooled from opposite wall while other walls are adiabatic. The governing equations which are continuity, momentum and energy equations are solved using finite volume method. The dimensionless heatfunction for nanofluid heat flow is defined and solved to determine heatline patterns. Calculations were performed for Rayleigh numbers of 10 3, 10 4 and 10 5, inclination angle of 0°, 30°, 60°and 90°, and nanoparticle fraction of 0, 0.02, 0.04, 0.06, 0.08 and 0.1. It is observed that heat transfer in the cavity increases by adding nanoparticles. The rate of increase is greater for the enclosures with low Rayleigh number. Visualization of heatline is successfully applied to nanoparticle convective flows. Based on the heatline patterns, three heat transfer regions are observed and discussed in details. © 2012 Elsevier Ltd. All rights reserved.Article Citation - WoS: 36Citation - Scopus: 37Visualization of Heat Flow Using Bejan's Heatline Due To Natural Convection of Water Near 4 °c in Thick Walled Porous Cavity(Elsevier Ltd., 2010) Varol, Yasin; Öztop, Hakan Fehmi; Mobedi, Moghtada; Pop, IoanA numerical study on natural convection heat transfer of cold water near 4 °C in a thick bottom walled cavity filled with a porous medium has been performed. It is assumed that the cavity is isothermally heated from the outside of the thick bottom wall and cooled from ceiling. The finite-difference method has been used to solve the governing partial differential equations of heat and fluid flow. Effects of thermal conductivity ratio, Rayleigh number and bottom wall thickness on heat transfer from the bottom to the ceiling have been studied. The heatline visualization technique has been used to demonstrate the path of heat transport through the enclosure. Moreover, streamlines and isotherms have been used to present fluid flow and temperature distributions. The obtained results show that multiple circulation cells are formed in the cavity and the local Nusselt numbers at the bottom wall and solid-fluid interface are highly affected by formed cells. The increase of Rayleigh number and thermal conductivity ratio increases heat transfer through the cavity. However, the increase of thickness of the bottom wall reduces the mean Nusselt number. Almost one-dimensional conduction heat transfer is observed in the solid bottom wall of the cavity. © 2010 Elsevier Ltd. All rights reserved.Article Citation - WoS: 81Citation - Scopus: 89Visualization of Natural Convection Heat Transport Using Heatline Method in Porous Non-Isothermally Heated Triangular Cavity(Elsevier Ltd., 2008) Varol, Yasin; Öztop, Hakan Fehmi; Mobedi, Moghtada; Pop, IoanNatural convection heat transfer in a porous media filled and non-isothermally heated from the bottom wall of triangular enclosure is analyzed using finite difference technique. Darcy law was used to write equations of porous media. Dimensionless heatfunction was used to visualize the heat transport due to buoyancy forces. Three different boundary conditions were applied for the vertical and inclined boundaries of triangular enclosures as Case I; both vertical and inclined walls were isothermal, Case II; vertical wall was adiabatic and inclined one was isothermal, Case III; vertical wall is isothermal and inclined one is adiabatic. A cosine function was utilized to get non-isothermal wall condition. The study was performed for different aspect ratios (0.25 ≤ AR ≤ 1.0) and Darcy-modified Rayleigh numbers (100 ≤ Ra ≤ 1000). It was observed that heat transfer enhancement was formed when vertical and inclined walls were isothermal while bottom wall was at non-uniform temperature. Heat transfer from bottom wall did not vary when the value of aspect ratio was higher than 0.50. In addition, heatline visualization technique was a useful technique for non-isothermally heated and porous media filled triangular enclosures. © 2008 Elsevier Ltd. All rights reserved.Article Citation - WoS: 25Citation - Scopus: 26Visualization of Heat Transport Using Dimensionless Heatfunction for Natural Convection and Conduction in an Enclosure With Thick Solid Ceiling(Elsevier Ltd., 2008) Mobedi, Moghtada; Öztop, Hakan FehmiA conjugate conduction-(natural)convection problem is numerically studied in order to present the application of dimensionless heatfunction for entire computational domain including solid and fluid regions in an enclosure with thick solid ceiling. The modified dimensionless heatfunction for solid region is defined to provide continuity of dimensionless heatfunction on solid-fluid interface. The enclosure is differentially heated from vertical walls, and horizontal walls are adiabatic. Finite difference method is employed to solve the set of governing equations. The dimensionless governing parameters for computations are: Rayleigh number (from 103 to 106), dimensionless ceiling wall thickness (0.05 and 0.5) and thermal conductivity ratio (from 1 to 100). The obtained results shows that the heat and fluid flows in the enclosure are considerably influenced by Rayleigh number and thermal conductivity ratio. Dimensionless wall thickness comparatively has less effect on heat transfer rate through the cavity. © 2008 Elsevier Ltd. All rights reserved.