Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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Access type: Open accessInstitution Author: search.filters.institutionAuthor.Sabet, Safa

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  • Article
    Citation - WoS: 36
    Citation - Scopus: 37
    Numerical Investigation of Melting Process for Phase Change Material (pcm) Embedded in Metal Foam Structures With Kelvin Cells at Pore Scale Level
    (Elsevier, 2023) Sabet, Safa; Buonomo, Bernardo; Sheremet, Mikhail A.; Manca, Oronzio
    The present numerical study analyzes the melting process of phase change material (PCM) embedded in a metallic foam structure at pore scale level. The computational domain consists of two different sizes of 3D cubic boxes. The analyzed domain is filled with Kelvin cell-structures with different Cell Per Length (CPL) and constant porosity of 0.956. A constant temperature, higher than the melting temperature of PCM, is assigned to one external surface of the enclosure, while the other surfaces are adiabatic. The conjugate problem for the heat transfer between the PCM and the solid structure with Kelvin cells is developed. Enthalpy-porosity method is used to describe the PCM melting process. The finite volume method is used to solve the conjugate heat transfer problem at pore scale level by Ansys-Fluent code. A comparison of different CPL values is reported in terms of liquid fraction, average temperature of the PCM, and energy storage. The comparison is also considered between the two different volumes of the cubic boxes. The presence of the metallic structured Kelvin cells increases the overall heat transfer rate and decreases the melting time. Results for smaller cavity indicates that as the CPL number increases, the time required for the PCM melting process decreases. Furthermore, the total heat accumulation process takes a shorter time to reach the maximum value. The melting time and the duration of heat accumulation are worsened for the large cubic box (L = 4 inch) at CLP>6. This is due to the dominant viscous effect, which decreases the velocity induced by the buoyancy forces because of higher contact surface area. In these cases, heat transfer between liquid and solid phases of the PCM decreases substantially. © 2023 Elsevier Ltd
  • Article
    Citation - WoS: 6
    Citation - Scopus: 6
    Numerical Study on Thermal Behaviors of Parallel Plate Systems for Sensible Thermal Energy Storage With Heat Loss
    (Elsevier, 2023) Sabet, Safa; Buonomo, Bernardo; Xie, Gongnan; Manca, Oronzio
    A numerical study on thermal energy storage systems with parallel plates to collect sensible heat is conducted with porous and direct model approaches. The simulations in a two-dimensional domain are performed with COMSOL Multiphysics commercial software. For the equivalent porous medium, the permeability and effective thermal conductivity as well as the specific area, and interfacial convective coefficient are numerically evaluated, considering a thermally and hydrodynamically fully developed flow. A stack of parallel plates is the system with assigned length and height, and the external heat losses effect is considered. The analysis allows to evaluate an optimized configuration as Channels Per Length (CPL) by means of a balance in the channels between pressure drop and heat transfer. Moreover, the effect of CPL values and heat loss from the parallel plate system is esti-mated in terms of charging time and heating capacity. The results exhibit that as the CPL increases, the time required for the charging process decreases while heat accumulation inside the system increases significantly. In fact, at the highest CPL, charging time is 2.7 times faster and the amount of heat accumulation is approximately 20% higher in adiabatic case. It is illustrated that the amount of heat accumulation inside the system varies considerably for different heat loss values. Ultimately, this study shows that porous model is more practical and accurate to be used for higher CPL cases.
  • Article
    Citation - WoS: 16
    Citation - Scopus: 17
    Thermal and Hydrodynamic Behavior of Forced Convection Gaseous Slip Flow in a Kelvin Cell Metal Foam
    (Elsevier, 2022) Sabet, Safa; Barışık, Murat; Buonomo, Bernardo; Manca, Oronzio
    Porous metallic foams are a key material in numerous thermal and hydraulic applications. Gas flows in such micro/nanoporous systems deviate from classical continuum descriptions due to nonequilibrium in gas dynamics, and the resulted heat and mass transport show variation by rarefaction. This study performed a wide range of pore-level analysis of convective gas flows in a Kelvin cell model at different porosities and working conditions. Rarefaction effects onto permeability and heat transfer coefficients were calculated through Darcy to Forchheimer flow regimes. Permeability increased up to 60% by increasing rarefaction while this enhancement decreased by increasing porosity. At the same time, rarefaction lessened inertial effects such that Forchheimer coefficients decreased substantially. At high flow velocities, the increase in rarefaction considerably decreased the effect of drag forces. Hence, hydrodynamic enhancement due to rarefaction was found to increase by increasing Reynolds number. On the other hand, positive influence of boundary slip and negative influence of temperature jump developing between gas and solid almost canceled each other for the studied low heat flux region of highly conductive metal foam structures. Hence, Nusselt numbers were found mostly related to Reynolds number independent from rarefaction. We described Nusselt value based on power law model as a function of Reynolds and porosity. Results and the proposed model are important to accurately predict the thermal and hydrodynamic performance of metal foams in the 80 PPI range.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 12
    Numerical Determination of Interfacial Heat Transfer Coefficient for an Aligned Dual Scale Porous Medium
    (Emerald Group Publishing, 2018) Sabet, Safa; Mobedi, Moghtada; Barışık, Murat; Nakayama, Akira
    Purpose Fluid flow and heat transfer in a dual scale porous media is investigated to determine the interfacial convective heat transfer coefficient, numerically. The studied porous media is a periodic dual scale porous media. It consists of the square rods which are permeable in an aligned arrangement. It is aimed to observe the enhancement of heat transfer through the porous media, which is important for thermal designers, by inserting intra-pores into the square rods. A special attention is given to the roles of size and number of intra-pores on the heat transfer enhancement through the dual scale porous media. The role of intra-pores on the pressure drop of air flow through porous media is also investigated by calculation and comparison of the friction coefficient. Design/methodology/approach To calculate the interfacial convective heat transfer coefficient, the governing equations which are continuity, momentum and energy equations are solved to determine velocity, pressure and temperature fields. As the dual scale porous structure is periodic, a representative elementary volume is generated, and the governing equations are numerically solved for the selected representative volume. By using the obtained velocity, pressure and temperature fields and using volume average definition, the volume average of aforementioned parameters is calculated and upscaled. Then, the interfacial convective heat transfer coefficient and the friction coefficient is numerically determined. The interparticle porosity is changed between 0.4 and 0.75, while the intraparticle varies between 0.2 and 0.75 to explore the effect of intra-pore on heat transfer enhancement. Findings The obtained Nusselt number values are compared with corresponding mono-scale porous media, and it is found that heat transfer through a porous medium can be enhanced threefold (without the increase of pressure drop) by inserting intraparticle pores in flow direction. For the porous media with low values of interparticle porosity (i.e. = 0.4), an optimum intraparticle porosity exists for which the highest heat transfer enhancement can be achieved. This value was found around 0.3 when the interparticle porosity was 0.4. Research limitations/implications The results of the study are interesting, especially from heat transfer enhancement point of view. However, further studies are required. For instance, studies should be performed to analyze the rate of the heat transfer enhancement for different shapes and arrangements of particles and a wider range of porosity. The other important parameter influencing heat transfer enhancement is the direction of pores. In the present study, the intraparticle pores are in flow direction; hence, the enhancement rate of heat transfer for different directions of pores must also be investigated. Practical implications The application of dual scale porous media is widely faced in daily life, nature and industry. The flowing of a fluid through a fiber mat, woven fiber bundles, multifilament textile fibers, oil filters and fractured porous media are some examples for the application of the heat and fluid flow through a dual scale porous media. Heat transfer enhancement. Social implications The enhancement of heat transfer is a significant topic that gained the attention of researchers in recent years. The importance of topic increases day-by-day because of further demands for downsizing of thermal equipment and heat recovery devices. The aim of thermal designers is to enhance heat transfer rate in thermal devices and to reduce their volume (and/or weight in some applications) by using lower mechanical power for cooling. Originality/value The present study might be the first study on determination of thermal transport properties of dual scale porous media yielded interesting results such as considerable enhancement of heat transfer by using proper intraparticle channels in a porous medium.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    A Pore Scale Study on Fluid Flow Through Two Dimensional Dual Scale Porous Media With Small Number of Intraparticle Pores
    (Walter de Gruyter GmbH, 2016) Sabet, Safa; Mobedi, Moghtada; Özgümüş, Türküler
    In the present study, the fluid flow in a periodic, non-isotropic dual scale porous media consisting of permeable square rods in inline arrangement is analyzed to determine permeability, numerically. The continuity and Navier-Stokes equations are solved to obtain the velocity and pressure distributions in the unit structures of the dual scale porous media for flows within Darcy region. Based on the obtained results, the intrinsic inter and intraparticle permeabilities and the bulk permeability tensor of the dual scale porous media are obtained for different values of inter and intraparticle porosities. The study is performed for interparticle porosities between 0.4 and 0.75 and for intraparticle porosities from 0.2 to 0.8. A correlation based on Kozeny-Carman relationship in terms of inter and intraparticle porosities and permeabilities is proposed to determine the bulk permeability tensor of the dual scale porous media.