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Ahmad Hajjar
ECAM Lyon, LabECAM, Université de Lyon, 69005 Lyon, France

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Journal article
Published: 09 March 2021 in Molecules
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Thermal energy storage units conventionally have the drawback of slow charging response. Thus, heat transfer enhancement techniques are required to reduce charging time. Using nanoadditives is a promising approach to enhance the heat transfer and energy storage response time of materials that store heat by undergoing a reversible phase change, so-called phase change materials. In the present study, a combination of such materials enhanced with the addition of nanometer-scale graphene oxide particles (called nano-enhanced phase change materials) and a layer of a copper foam is proposed to improve the thermal performance of a shell-and-tube latent heat thermal energy storage (LHTES) unit filled with capric acid. Both graphene oxide and copper nanoparticles were tested as the nanometer-scale additives. A geometrically nonuniform layer of copper foam was placed over the hot tube inside the unit. The metal foam layer can improve heat transfer with an increase of the composite thermal conductivity. However, it suppressed the natural convection flows and could reduce heat transfer in the molten regions. Thus, a metal foam layer with a nonuniform shape can maximize thermal conductivity in conduction-dominant regions and minimize its adverse impacts on natural convection flows. The heat transfer was modeled using partial differential equations for conservations of momentum and heat. The finite element method was used to solve the partial differential equations. A backward differential formula was used to control the accuracy and convergence of the solution automatically. Mesh adaptation was applied to increase the mesh resolution at the interface between phases and improve the quality and stability of the solution. The impact of the eccentricity and porosity of the metal foam layer and the volume fraction of nanoparticles on the energy storage and the thermal performance of the LHTES unit was addressed. The layer of the metal foam notably improves the response time of the LHTES unit, and a 10% eccentricity of the porous layer toward the bottom improved the response time of the LHTES unit by 50%. The presence of nanoadditives could reduce the response time (melting time) of the LHTES unit by 12%, and copper nanoparticles were slightly better than graphene oxide particles in terms of heat transfer enhancement. The design parameters of the eccentricity, porosity, and volume fraction of nanoparticles had minimal impact on the thermal energy storage capacity of the LHTES unit, while their impact on the melting time (response time) was significant. Thus, a combination of the enhancement method could practically reduce the thermal charging time of an LHTES unit without a significant increase in its size.

ACS Style

Mohammad Ghalambaz; Seyed Mehryan; Kasra Ayoubloo; Ahmad Hajjar; Mohamad El Kadri; Obai Younis; Mohsen Pour; Christopher Hulme-Smith. Thermal Energy Storage and Heat Transfer of Nano-Enhanced Phase Change Material (NePCM) in a Shell and Tube Thermal Energy Storage (TES) Unit with a Partial Layer of Eccentric Copper Foam. Molecules 2021, 26, 1491 .

AMA Style

Mohammad Ghalambaz, Seyed Mehryan, Kasra Ayoubloo, Ahmad Hajjar, Mohamad El Kadri, Obai Younis, Mohsen Pour, Christopher Hulme-Smith. Thermal Energy Storage and Heat Transfer of Nano-Enhanced Phase Change Material (NePCM) in a Shell and Tube Thermal Energy Storage (TES) Unit with a Partial Layer of Eccentric Copper Foam. Molecules. 2021; 26 (5):1491.

Chicago/Turabian Style

Mohammad Ghalambaz; Seyed Mehryan; Kasra Ayoubloo; Ahmad Hajjar; Mohamad El Kadri; Obai Younis; Mohsen Pour; Christopher Hulme-Smith. 2021. "Thermal Energy Storage and Heat Transfer of Nano-Enhanced Phase Change Material (NePCM) in a Shell and Tube Thermal Energy Storage (TES) Unit with a Partial Layer of Eccentric Copper Foam." Molecules 26, no. 5: 1491.

Journal article
Published: 09 March 2021 in Molecules
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A wavy shape was used to enhance the thermal heat transfer in a shell-tube latent heat thermal energy storage (LHTES) unit. The thermal storage unit was filled with CuO–coconut oil nano-enhanced phase change material (NePCM). The enthalpy-porosity approach was employed to model the phase change heat transfer in the presence of natural convection effects in the molten NePCM. The finite element method was applied to integrate the governing equations for fluid motion and phase change heat transfer. The impact of wave amplitude and wave number of the heated tube, as well as the volume concertation of nanoparticles on the full-charging time of the LHTES unit, was addressed. The Taguchi optimization method was used to find an optimum design of the LHTES unit. The results showed that an increase in the volume fraction of nanoparticles reduces the charging time. Moreover, the waviness of the tube resists the natural convection flow circulation in the phase change domain and could increase the charging time.

ACS Style

Mohammad Ghalambaz; S.A.M. Mehryan; Ahmad Hajjar; Mohammad Shdaifat; Obai Younis; Pouyan Talebizadehsardari; Wahiba Yaïci. Thermal Charging Optimization of a Wavy-Shaped Nano-Enhanced Thermal Storage Unit. Molecules 2021, 26, 1496 .

AMA Style

Mohammad Ghalambaz, S.A.M. Mehryan, Ahmad Hajjar, Mohammad Shdaifat, Obai Younis, Pouyan Talebizadehsardari, Wahiba Yaïci. Thermal Charging Optimization of a Wavy-Shaped Nano-Enhanced Thermal Storage Unit. Molecules. 2021; 26 (5):1496.

Chicago/Turabian Style

Mohammad Ghalambaz; S.A.M. Mehryan; Ahmad Hajjar; Mohammad Shdaifat; Obai Younis; Pouyan Talebizadehsardari; Wahiba Yaïci. 2021. "Thermal Charging Optimization of a Wavy-Shaped Nano-Enhanced Thermal Storage Unit." Molecules 26, no. 5: 1496.

Journal article
Published: 07 March 2021 in Sustainability
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The melting heat transfer of nano-enhanced phase change materials was addressed in a thermal energy storage unit. A heated U-shape tube was placed in a cylindrical shell. The cross-section of the tube is a petal-shape, which can have different amplitudes and wave numbers. The shell is filled with capric acid with a fusion temperature of 32 °C. The copper (Cu)/graphene oxide (GO) type nanoparticles were added to capric acid to improve its heat transfer properties. The enthalpy-porosity approach was used to model the phase change heat transfer in the presence of natural convection heat transfer effects. A novel mesh adaptation method was used to track the phase change melting front and produce high-quality mesh at the phase change region. The impacts of the volume fraction of nanoparticles, the amplitude and number of petals, the distance between tubes, and the angle of tube placements were investigated on the thermal energy rate and melting-time in the thermal energy storage unit. An average charging power can be raised by up to 45% by using petal shape tubes compared to a plain tube. The nanoadditives could improve the heat transfer by 7% for Cu and 11% for GO nanoparticles compared to the pure phase change material.

ACS Style

Mohammad Ghalambaz; Seyed Mehryan; Reza Feeoj; Ahmad Hajjar; Obai Younis; Pouyan Talebizadehsardari; Wahiba Yaïci. Effect of the Quasi-Petal Heat Transfer Tube on the Melting Process of the Nano-Enhanced Phase Change Substance in a Thermal Energy Storage Unit. Sustainability 2021, 13, 2871 .

AMA Style

Mohammad Ghalambaz, Seyed Mehryan, Reza Feeoj, Ahmad Hajjar, Obai Younis, Pouyan Talebizadehsardari, Wahiba Yaïci. Effect of the Quasi-Petal Heat Transfer Tube on the Melting Process of the Nano-Enhanced Phase Change Substance in a Thermal Energy Storage Unit. Sustainability. 2021; 13 (5):2871.

Chicago/Turabian Style

Mohammad Ghalambaz; Seyed Mehryan; Reza Feeoj; Ahmad Hajjar; Obai Younis; Pouyan Talebizadehsardari; Wahiba Yaïci. 2021. "Effect of the Quasi-Petal Heat Transfer Tube on the Melting Process of the Nano-Enhanced Phase Change Substance in a Thermal Energy Storage Unit." Sustainability 13, no. 5: 2871.

Journal article
Published: 01 March 2021 in Sustainability
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A Nano-Encapsulated Phase-Change Material (NEPCM) suspension is made of nanoparticles containing a Phase Change Material in their core and dispersed in a fluid. These particles can contribute to thermal energy storage and heat transfer by their latent heat of phase change as moving with the host fluid. Thus, such novel nanoliquids are promising for applications in waste heat recovery and thermal energy storage systems. In the present research, the mixed convection of NEPCM suspensions was addressed in a wavy wall cavity containing a rotating solid cylinder. As the nanoparticles move with the liquid, they undergo a phase change and transfer the latent heat. The phase change of nanoparticles was considered as temperature-dependent heat capacity. The governing equations of mass, momentum, and energy conservation were presented as partial differential equations. Then, the governing equations were converted to a non-dimensional form to generalize the solution, and solved by the finite element method. The influence of control parameters such as volume concentration of nanoparticles, fusion temperature of nanoparticles, Stefan number, wall undulations number, and as well as the cylinder size, angular rotation, and thermal conductivities was addressed on the heat transfer in the enclosure. The wall undulation number induces a remarkable change in the Nusselt number. There are optimum fusion temperatures for nanoparticles, which could maximize the heat transfer rate. The increase of the latent heat of nanoparticles (a decline of Stefan number) boosts the heat transfer advantage of employing the phase change particles.

ACS Style

S. Mehryan; Kaamran Raahemifar; Leila Gargari; Ahmad Hajjar; Mohamad El Kadri; Obai Younis; Mohammad Ghalambaz. Latent Heat Phase Change Heat Transfer of a Nanoliquid with Nano–Encapsulated Phase Change Materials in a Wavy-Wall Enclosure with an Active Rotating Cylinder. Sustainability 2021, 13, 2590 .

AMA Style

S. Mehryan, Kaamran Raahemifar, Leila Gargari, Ahmad Hajjar, Mohamad El Kadri, Obai Younis, Mohammad Ghalambaz. Latent Heat Phase Change Heat Transfer of a Nanoliquid with Nano–Encapsulated Phase Change Materials in a Wavy-Wall Enclosure with an Active Rotating Cylinder. Sustainability. 2021; 13 (5):2590.

Chicago/Turabian Style

S. Mehryan; Kaamran Raahemifar; Leila Gargari; Ahmad Hajjar; Mohamad El Kadri; Obai Younis; Mohammad Ghalambaz. 2021. "Latent Heat Phase Change Heat Transfer of a Nanoliquid with Nano–Encapsulated Phase Change Materials in a Wavy-Wall Enclosure with an Active Rotating Cylinder." Sustainability 13, no. 5: 2590.

Journal article
Published: 26 February 2021 in Applied Thermal Engineering
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Energy storage systems based on phase change materials are very innovative and useful in different engineering applications. The present study deals with numerical simulation of energy transport performance in a shell and tube energy storage system, including the paraffin wax or copper foam insertion with paraffin wax. The mathematical description of the considered problem consists of the basic equations grounded on the conservation laws with appropriate initial and boundary conditions. These equations were solved by the finite element method. The developed code was verified using the mesh sensitivity analysis and numerical data of other authors. Effects of the porosity, Rayleigh number, melting temperature, heat pipes location on melting flow structures and energy transport, and Nusselt number and melting volume fraction were scrutinized for charging and discharging modes. It was found that in the case of porous metal foam, the phase change intensity increases for the mentioned two regimes in comparison with pure paraffin wax. The vertical placement of the heating tubes results in the best charging time.

ACS Style

Ali Veismoradi; Mohammad Ghalambaz; Hassan Shirivand; Ahmad Hajjar; Abdulmajeed Mohamad; Mikhail Sheremet; Ali Chamkha; Obai Younis. Study of paraffin-based composite-phase change materials for a shell and tube energy storage system: A mesh adaptation approach. Applied Thermal Engineering 2021, 190, 116793 .

AMA Style

Ali Veismoradi, Mohammad Ghalambaz, Hassan Shirivand, Ahmad Hajjar, Abdulmajeed Mohamad, Mikhail Sheremet, Ali Chamkha, Obai Younis. Study of paraffin-based composite-phase change materials for a shell and tube energy storage system: A mesh adaptation approach. Applied Thermal Engineering. 2021; 190 ():116793.

Chicago/Turabian Style

Ali Veismoradi; Mohammad Ghalambaz; Hassan Shirivand; Ahmad Hajjar; Abdulmajeed Mohamad; Mikhail Sheremet; Ali Chamkha; Obai Younis. 2021. "Study of paraffin-based composite-phase change materials for a shell and tube energy storage system: A mesh adaptation approach." Applied Thermal Engineering 190, no. : 116793.

Journal article
Published: 25 February 2021 in Molecules
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Thermal energy storage is a technique that has the potential to contribute to future energy grids to reduce fluctuations in supply from renewable energy sources. The principle of energy storage is to drive an endothermic phase change when excess energy is available and to allow the phase change to reverse and release heat when energy demand exceeds supply. Unwanted charge leakage and low heat transfer rates can limit the effectiveness of the units, but both of these problems can be mitigated by incorporating a metal foam into the design of the storage unit. This study demonstrates the benefits of adding copper foam into a thermal energy storage unit based on capric acid enhanced by copper nanoparticles. The volume fraction of nanoparticles and the location and porosity of the foam were optimized using the Taguchi approach to minimize the charge leakage expected from simulations. Placing the foam layer at the bottom of the unit with the maximum possible height and minimum porosity led to the lowest charge time. The optimum concentration of nanoparticles was found to be 4 vol.%, while the maximu possible concentration was 6 vol.%. The use of an optimized design of the enclosure and the optimum fraction of nanoparticles led to a predicted charging time for the unit that was approximately 58% shorter than that of the worst design. A sensitivity analysis shows that the height of the foam layer and its porosity are the dominant variables, and the location of the porous layer and volume fraction of nanoparticles are of secondary importance. Therefore, a well-designed location and size of a metal foam layer could be used to improve the charging speed of thermal energy storage units significantly. In such designs, the porosity and the placement-location of the foam should be considered more strongly than other factors.

ACS Style

Mohammad Ghalambaz; Seyed Mehryan; Ahmad Hajjar; Obai Younis; Mikhail Sheremet; Mohsen Pour; Christopher Hulme-Smith. Phase-Transition Thermal Charging of a Channel-Shape Thermal Energy Storage Unit: Taguchi Optimization Approach and Copper Foam Inserts. Molecules 2021, 26, 1235 .

AMA Style

Mohammad Ghalambaz, Seyed Mehryan, Ahmad Hajjar, Obai Younis, Mikhail Sheremet, Mohsen Pour, Christopher Hulme-Smith. Phase-Transition Thermal Charging of a Channel-Shape Thermal Energy Storage Unit: Taguchi Optimization Approach and Copper Foam Inserts. Molecules. 2021; 26 (5):1235.

Chicago/Turabian Style

Mohammad Ghalambaz; Seyed Mehryan; Ahmad Hajjar; Obai Younis; Mikhail Sheremet; Mohsen Pour; Christopher Hulme-Smith. 2021. "Phase-Transition Thermal Charging of a Channel-Shape Thermal Energy Storage Unit: Taguchi Optimization Approach and Copper Foam Inserts." Molecules 26, no. 5: 1235.

Journal article
Published: 23 February 2021 in Sustainability
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The melting heat transfer of CuO—coconut oil embedded in a non-uniform copper metal foam—was addressed. Copper foam is placed in a channel-shaped Thermal Energy Storage (TES) unit heated from one side. The foam is non-uniform with a linear porosity gradient in a direction perpendicular to the heated surface. The finite element method was applied to simulate natural convection flow and phase change heat transfer in the TES unit. The results showed that the porosity gradient could significantly boost the melting rate and stored energy rate in the TES unit. The best non-uniform porosity corresponds to a case in which the maximum porosity is next to a heated surface. The variation of the unit placement’s inclination angle is only important in the final stage of charging, where there is a dominant natural convection flow. The variation of porous pore size induces minimal impact on the phase change rate, except in the case of a large pore size of 30 pore density (PPI). The presence of nanoparticles could increase or decrease the charging time. However, using a 4% volume fraction of nanoparticles could mainly reduce the charging time.

ACS Style

Mohammad Ghalambaz; S. Mehryan; Ahmad Hajjar; Mehdi Fteiti; Obai Younis; Pouyan Sardari; Wahiba Yaïci. Latent Heat Thermal Storage in Non-Uniform Metal Foam Filled with Nano-Enhanced Phase Change Material. Sustainability 2021, 13, 2401 .

AMA Style

Mohammad Ghalambaz, S. Mehryan, Ahmad Hajjar, Mehdi Fteiti, Obai Younis, Pouyan Sardari, Wahiba Yaïci. Latent Heat Thermal Storage in Non-Uniform Metal Foam Filled with Nano-Enhanced Phase Change Material. Sustainability. 2021; 13 (4):2401.

Chicago/Turabian Style

Mohammad Ghalambaz; S. Mehryan; Ahmad Hajjar; Mehdi Fteiti; Obai Younis; Pouyan Sardari; Wahiba Yaïci. 2021. "Latent Heat Thermal Storage in Non-Uniform Metal Foam Filled with Nano-Enhanced Phase Change Material." Sustainability 13, no. 4: 2401.

Journal article
Published: 17 October 2020 in Advanced Powder Technology
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The nano encapsulated phase change materials are of the great energy storage potential in various engineering applications. Since they are new nanomaterials, new models for understanding their thermal behavior and capability are essential. This work aims to investigate the unsteady thermal behavior of Nano-Encapsulated Phase Change Material (NEPCM) suspensions in a cylindrical cavity. The particles contain a Phase Change Material (PCM) core, which can absorb/release a substantial amount of thermal energy upon phase change. The phase change particles are well dispersed in a liquid fluid and freely move along with the fluid. The flow, heat transfer, and the particle phase change were modeled using partial differential equations. A non-dimensional approach was employed to generalize the study. The unsteady charging and discharging behavior of the NEPCM suspension are investigated for the volume fraction of the NEPCM particles, fusion temperature of nanoparticles, Stefan number, and the Rayleigh number. Numerical results show that an increment in the Stefan number, i.e., Ste, can significantly reduce the Nusselt number, i.e., Nua, at the charging mode of the system. However, the dependency of the Nua at the discharging mode on the Ste is negligible. Also, it was found that the effect of the fusion temperature of the particle’s core (θf) on heat transfer depends on the working mode of the system. In the charging mode, using a higher value of θf decreases the heat transfer rate. Reversibly, a higher value of θf inhibits the Nua during discharging state. Furthermore, the results show that for Ra = 106, Ste = 0.2, and θf = 0.1, a rise of ϕ from 0 to 0.05 leads in about 1.73 and 1.55 times of improvement in the value of Nua for the cases of the melting and solidification of the core of NEPCM particles.

ACS Style

Mohammad Ghalambaz; S.A.M Mehryan; Nemat Mashoofi; Ahmad Hajjar; Ali J. Chamkha; Mikhail Sheremet; Obai Younis. Free convective melting-solidification heat transfer of nano-encapsulated phase change particles suspensions inside a coaxial pipe. Advanced Powder Technology 2020, 31, 4470 -4481.

AMA Style

Mohammad Ghalambaz, S.A.M Mehryan, Nemat Mashoofi, Ahmad Hajjar, Ali J. Chamkha, Mikhail Sheremet, Obai Younis. Free convective melting-solidification heat transfer of nano-encapsulated phase change particles suspensions inside a coaxial pipe. Advanced Powder Technology. 2020; 31 (11):4470-4481.

Chicago/Turabian Style

Mohammad Ghalambaz; S.A.M Mehryan; Nemat Mashoofi; Ahmad Hajjar; Ali J. Chamkha; Mikhail Sheremet; Obai Younis. 2020. "Free convective melting-solidification heat transfer of nano-encapsulated phase change particles suspensions inside a coaxial pipe." Advanced Powder Technology 31, no. 11: 4470-4481.

Journal article
Published: 05 August 2020 in Journal of Energy Storage
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In the present study, the effect of using a layer of metal foam in a composite metal foam – phase change heatsink is addressed. The bottom of the heatsink is subjected to a pulse heat flux, while the top of the heatsink is exposed to an external cooling convective flow. The melting/solidification of the Phase Change Materials (PCMs) is modeled using the enthalpy porosity approach. The partial differential equations governing the natural convective flow and the heat transfer in the clear flow region and porous layers of the heatsink are introduced and transformed into a non-dimensional form using non-dimensional variables. The Finite Element Method (FEM) with an automatic time-step and grid adaptation is employed to solve the governing equations. The model and the numerical code are validated by comparison to several results obtained in recent works available in the literature. The effect of the surrounding heat transfer by convection and the fusion temperature of the PCM on the heatsink performance and on the phase change behavior is investigated. The results show that melting heat transfer occurs during the activation of the pulse heat flux while the solidification commences with a small delay after the pulse heat flux turns off. The heatsink presents a major benefit when the external cooling power is weak. Moreover, a heatsink with a lower fusion temperature shows a better cooling efficiency. The presence of a metal foam layer notably improves the cooling efficiency of the heatsink. However, the location of the porous layer shows a minimal effect on the heatsink efficiency.

ACS Style

Ahmad Hajjar; Esmail Jamesahar; Hassan Shirivand; Mohammad Ghalambaz; Roohollah Babaei Mahani. Transient phase change heat transfer in a metal foam-phase change material heatsink subject to a pulse heat flux. Journal of Energy Storage 2020, 31, 101701 .

AMA Style

Ahmad Hajjar, Esmail Jamesahar, Hassan Shirivand, Mohammad Ghalambaz, Roohollah Babaei Mahani. Transient phase change heat transfer in a metal foam-phase change material heatsink subject to a pulse heat flux. Journal of Energy Storage. 2020; 31 ():101701.

Chicago/Turabian Style

Ahmad Hajjar; Esmail Jamesahar; Hassan Shirivand; Mohammad Ghalambaz; Roohollah Babaei Mahani. 2020. "Transient phase change heat transfer in a metal foam-phase change material heatsink subject to a pulse heat flux." Journal of Energy Storage 31, no. : 101701.

Journal article
Published: 08 June 2020 in Energies
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The present investigation addressed the entropy generation, fluid flow, and heat transfer regarding Cu-Al 2 O 3 -water hybrid nanofluids into a complex shape enclosure containing a hot-half partition were addressed. The sidewalls of the enclosure are made of wavy walls including cold isothermal temperature while the upper and lower surfaces remain insulated. The governing equations toward conservation of mass, momentum, and energy were introduced into the form of partial differential equations. The second law of thermodynamic was written for the friction and thermal entropy productions as a function of velocity and temperatures. The governing equations occurred molded into a non-dimensional pattern and explained through the finite element method. Outcomes were investigated for Cu-water, Al 2 O 3 -water, and Cu-Al 2 O 3 -water nanofluids to address the effect of using composite nanoparticles toward the flow and temperature patterns and entropy generation. Findings show that using hybrid nanofluid improves the Nusselt number compared to simple nanofluids. In the case of low Rayleigh numbers, such enhancement is more evident. Changing the geometrical aspects of the cavity induces different effects toward the entropy generation and Bejan number. Generally, the global entropy generation for Cu-Al 2 O 3 -water hybrid nanofluid takes places between the entropy generation values regarding Cu-water and Al 2 O 3 -water nanofluids.

ACS Style

Ammar I. Alsabery; Ishak Hashim; Ahmad Hajjar; Mohammad Ghalambaz; Sohail Nadeem; Mohsen Saffari Pour. Entropy Generation and Natural Convection Flow of Hybrid Nanofluids in a Partially Divided Wavy Cavity Including Solid Blocks. Energies 2020, 13, 2942 .

AMA Style

Ammar I. Alsabery, Ishak Hashim, Ahmad Hajjar, Mohammad Ghalambaz, Sohail Nadeem, Mohsen Saffari Pour. Entropy Generation and Natural Convection Flow of Hybrid Nanofluids in a Partially Divided Wavy Cavity Including Solid Blocks. Energies. 2020; 13 (11):2942.

Chicago/Turabian Style

Ammar I. Alsabery; Ishak Hashim; Ahmad Hajjar; Mohammad Ghalambaz; Sohail Nadeem; Mohsen Saffari Pour. 2020. "Entropy Generation and Natural Convection Flow of Hybrid Nanofluids in a Partially Divided Wavy Cavity Including Solid Blocks." Energies 13, no. 11: 2942.

Journal article
Published: 01 February 2020 in Journal of Energy Storage
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The free convective flow of a Nano-Encapsulated Phase Change Material (NEPCM) suspension in an eccentric annulus is investigated numerically. The inner cylinder is heated and kept at a temperature higher than that of the outer cylinder. The core of the NEPCM particles is made of nonadecane while the shell is made of Polyurethane. The nanoparticles are dispersed in water as the base fluid. The equations governing the flow and heat transfer of the NEPCM suspension in the annulus are developed and written in the non-dimensional form. The numerical solutions of these equations are obtained using the finite element method. The validity of the numerical method is ensured by comparing its predictions to the results of previously published studies. The main outcomes point out to the impact of the volume fraction of the NEPCM particles and Stefan number on the thermal and hydrodynamic characteristics of the suspension. A 5% volume fraction represents the optimal value for heat transfer enhancement. Heat transfer is also enhanced when the fusion temperature of the NEPCM core is far from the temperatures of the hot and cold walls. Furthermore, increasing the annulus eccentricity and moving the inner cylinder towards the top tends to inhibit heat transfer in the annulus.

ACS Style

S.A.M. Mehryan; Mohammad Ghalambaz; Leila Sasani Gargari; Ahmad Hajjar; Mikhail Sheremet. Natural convection flow of a suspension containing nano-encapsulated phase change particles in an eccentric annulus. Journal of Energy Storage 2020, 28, 101236 .

AMA Style

S.A.M. Mehryan, Mohammad Ghalambaz, Leila Sasani Gargari, Ahmad Hajjar, Mikhail Sheremet. Natural convection flow of a suspension containing nano-encapsulated phase change particles in an eccentric annulus. Journal of Energy Storage. 2020; 28 ():101236.

Chicago/Turabian Style

S.A.M. Mehryan; Mohammad Ghalambaz; Leila Sasani Gargari; Ahmad Hajjar; Mikhail Sheremet. 2020. "Natural convection flow of a suspension containing nano-encapsulated phase change particles in an eccentric annulus." Journal of Energy Storage 28, no. : 101236.

Journal article
Published: 27 December 2019 in Advanced Powder Technology
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The free convection phase change heat transfer of a suspension comprising Nano-Encapsulated Phase Change Materials (NEPCMs) in a porous space is theoretically addressed. The core of the nanoparticles is made of a phase change material and encapsulated in a thin shell. Hence, the core of the nanoparticles suspension undergoes a phase change at its fusion temperature and release/store large amounts of latent heat. The phase change of nanoparticles is modeled using a sine shape temperature-dependent heat capacity function. Darcy-Brinkman model is used to model the flow in the porous medium. The governing equations including the conservation of mass, momentum, and heat are transformed into a non-dimensional form before being solved by the finite element method in a structured non-uniform mesh. The influence of the porosity, Darcy number, Rayleigh number, fusion temperature of nanoparticles, and the unsteady time-periodic boundary conditions on the thermal behavior of the porous medium in the presence of NEPMC is investigated. The results show that the presence of NEPCM particles improves the heat transfer. The increase of porosity improves the heat transfer when the volumetric concentrations of NEPCM particles are higher than 3%. There exists an optimal dimensionless fusion temperature of NEPCM nanoparticles for the interval [0.25; 0.75].

ACS Style

Mohammad Ghalambaz; S.A.M. Mehryan; Ahmad Hajjar; Ali Veisimoradi. Unsteady natural convection flow of a suspension comprising Nano-Encapsulated Phase Change Materials (NEPCMs) in a porous medium. Advanced Powder Technology 2019, 31, 954 -966.

AMA Style

Mohammad Ghalambaz, S.A.M. Mehryan, Ahmad Hajjar, Ali Veisimoradi. Unsteady natural convection flow of a suspension comprising Nano-Encapsulated Phase Change Materials (NEPCMs) in a porous medium. Advanced Powder Technology. 2019; 31 (3):954-966.

Chicago/Turabian Style

Mohammad Ghalambaz; S.A.M. Mehryan; Ahmad Hajjar; Ali Veisimoradi. 2019. "Unsteady natural convection flow of a suspension comprising Nano-Encapsulated Phase Change Materials (NEPCMs) in a porous medium." Advanced Powder Technology 31, no. 3: 954-966.

Journal article
Published: 15 October 2019 in International Journal of Mechanical Sciences
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The natural convection of a Nano Encapsulated Phase Change Materials (NEPCMs) suspension in a cavity with a hot wall having a time-periodic temperature is investigated. The top and bottom walls of the enclosure are insulated, the right side wall is kept at a constant temperature of Tc while the left side wall is considered as hot wall and is subjected to a time-periodic temperature. The NEPCM consist of capsules with phase change material PCM in their core. The phase change core of the capsules is covered by a shell. During the fusion or the solidification of the core, the phase change will absorb or release heat in the surrounding, when the temperature is close to the PCM fusion temperature. The partial differential equations governing the flow and heat transfer in the enclosure are formulated in the dimensionless form, and affective key dimensionless numbers and parameters are introduced. The finite element method is used to solve the governing equations. The accuracy of the results is verified by comparison to the benchmark solutions available in the literature. The average Nusselt number in the enclosure, as an indicator of the heat transfer performance, is analyzed. It is shown that the average Nusselt number in the enclosure follows a periodic variation with the same frequency of the temperature of the hot wall and with an amplitude that varies correspondingly with the temperature amplitude. The heat transfer in the cavity is enhanced when a higher fraction ϕ of the NEPCM is used, and a fraction of 5% provides the highest heat transfer. Increasing the volume fraction of nanoparticles from 2.5% to 5% enhanced the average Nusselt number by 21% and the maximum value of Nusselt number by 18.5%. The fusion temperature of nanocapsules is an important parameter affecting the thermal performance of the enclosure, mainly, when the fusion temperature is notably different from cold or hot-wall temperatures.

ACS Style

Ahmad Hajjar; S.A.M. Mehryan; Mohammad Ghalambaz. Time periodic natural convection heat transfer in a nano-encapsulated phase-change suspension. International Journal of Mechanical Sciences 2019, 166, 105243 .

AMA Style

Ahmad Hajjar, S.A.M. Mehryan, Mohammad Ghalambaz. Time periodic natural convection heat transfer in a nano-encapsulated phase-change suspension. International Journal of Mechanical Sciences. 2019; 166 ():105243.

Chicago/Turabian Style

Ahmad Hajjar; S.A.M. Mehryan; Mohammad Ghalambaz. 2019. "Time periodic natural convection heat transfer in a nano-encapsulated phase-change suspension." International Journal of Mechanical Sciences 166, no. : 105243.