Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 120Citation - Scopus: 136Numerical Study on Latent Thermal Energy Storage Systems With Aluminum Foam in Local Thermal Equilibrium(Elsevier, 2019) Buonomo, Bernardo; Çelik, Hasan; Ercole, Davide; Manca, Oronzio; Mobedi, MoghtadaThe paper analyzes the behavior of a Latent Heat Thermal Energy Storage system (LHTES) with a Phase Change Material (PCM), with and without aluminum foam. A numerical investigation in a two-dimensional domain is accomplished to investigate on the system thermal evolution. The enthalpy-porosity method is used to describe the PCM melting. The open-celled aluminum foam is described as a porous medium by means of the Darcy-Forchheimer law. A hollow cylinder represents the considered thermal energy storage and it consists of the enclosure between two concentric shell tubes. The external surface of the internal tube is at assigned temperature with a value greater than the melting PCM temperature, while the other surfaces are adiabatic. Local thermal equilibrium (LTE) is numerically adopted for modelling the heat transfer between the PCM and the solid matrix in aluminum foam. In the case with metal foam, simulations for different porosities are performed. A comparison in term of liquid fraction, average temperature of the system, temperature fields, stream function and a performance parameter are made between the clean case and porous assisted case for the different porosities. A scale analysis is developed for evaluating the time and the melting zone in different regimes (i.e. conduction, mixed conduction-convective and convective) during the melting processes of the PCM in porous media. Numerical simulation shows that aluminum foam increases overall heat transfer by a magnitude of two, with respect to the clean case.Article Citation - WoS: 15Citation - Scopus: 16A Pore Scale Analysis for Determination of Interfacial Convective Heat Transfer Coefficient for Thin Periodic Porousmedia Undermixed Convection(Emerald Group Publishing Ltd., 2017) Çelik, Hasan; Mobedi, Moghtada; Manca, Oronzio; Özkol, ÜnverPurpose - The purpose of this study is to determine interfacial convective heat transfer coefficient numerically, for a porous media consisting of square blocks in inline arrangement under mixed convection heat transfer. Design/methodology/approach - The continuity, momentum and energy equations are solved in dimensionless form for a representative elementary volume of porous media, numerically. The velocity and temperature fields for different values of porosity, Ri and Re numbers are obtained. The study is performed for the range of Ri number from 0.01 to 10, Re number from 100 to 500 and porosity value from 0.51 to 0.96. Based on the obtained results, the value of the interfacial convective heat transfer coefficient is calculated by using volume average method. Findings - It was found that at low porosities (such as 0.51), the interfacial Nusselt number does not considerably change with Ri and Re numbers. However, for porous media with high Ri number and porosity (such as 10 and 0.51, respectively), secondary flows occur in the middle of the channel between rods improving heat transfer between solid and fluid, considerably. It is shown that the available correlations of interfacial heat transfer coefficient suggested for forced convection can be used for mixed convection for the porous media with low porosity (such as 0.51) or for the flow with low Ri number (such as 0.01). Originality/value - To the best of the authors' knowledge, there is no study on determination of interfacial convective heat transfer coefficient for mixed convection in porous media in literature. The present study might be the first study providing an accurate idea on the range of this important parameter, which will be useful particularly for researchers who study on mixed convection heat transfer in porous media, macroscopically.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.