Publications

Solar photovoltaic must be equipped with a cooling unit to gain thermal performance and in present research, a new configuration of unit for photovoltaic-thermal has been presented. To enhance the electrical performance, a thermoelectric layer has been attached above the absorber. Two regions for hybrid nanofluid flow exist within the system including a circular duct equipped with a turbulator and mini channel equipped with jet impingement. The regimes of both zones are laminar and single phase formulation for properties of hybrid nanomaterial has been utilized. With selecting the turbulator with the greatest level of revolution, the electrical efficiency enhances about 1.41% and useful heat enhances about 5.72%. The amount of performance factor for the case with highest revolution is 1.25 which means the good hydrothermal performance. The mentioned case has been equipped with confined jets and the amount of electrical and thermal performance of the best case reaches 15.50% and 85.30%. The temperature uniformity of the new design improves about 46.89%.

Since advective transport in a ferrofluid can be controlled by using an external magnetic field, magnetic nanofluid (ferrofluid) has various applications to heat transfer processes. Unlike free or forced convection, Ferrohydrodynamic convection is not yet well described. In the literature we see papers with constant magnetic fields; but the assumptions are not accurate, since the fields do not comply with the Maxwell’s equations of electromagnetism. In this study, forced convection heat transfer in a semi annulus lid under the influence of a variable magnetic field is studied. The enclosure is filled with ferrofluid (Fe3O4–water). Control Volume based Finite Element Method (CVFEM) is used to solve the governing equations considering both Ferrohydrodynamic (FHD) and Magnetohydrodynamic (MHD) effects. It is assumed that the magnetization of the fluid is varying linearly with temperature and magnetic field intensity. The effects Reynolds number, nanoparticle volume fraction parameter, magnetic number arising from FHD, and Hartmann number arising from MHD are analyzed. Obtained results indicate that the effects of Kelvin forces are more pronounced for high Reynolds number. Heat transfer enhancement has direct relationship with the Reynolds number and the magnetic number; while it has inverse relationship with the Hartmann number.

In the present book, various applications of microfluidics and nanofluidics are introduced. Microfluidics and nanofluidics span a broad array of disciplines including mechanical, materials, and electrical engineering, surface science, chemistry, physics and biology. Also, this book deals with transport and interactions of colloidal particles and biomolecules in microchannels, which have great importance to many microfluidic applications, such as drug delivery in life science, microchannel heat exchangers in electronic cooling, and food processing industry. Furthermore, this book focuses on a detailed description of the thermal transport behavior, challenges and implications that involve the development and use of HTFs under the influence of atomistic-scale structures and industrial applications.

Porous media has different applications in building and geothermal sciences, engineering, and agriculture. An introduction to the application of porous media and previous works in this field is presented first. The governing equations for flow and heat transfer in a porous media with a Brinkmann-extended Darcy model are derived. Pressure gradients are eliminated from momentum equations using the vorticity stream function method. The control volume finite element method is used for solving such a problem in different geometries. Effects of porosity, Darcy number, and Rayleigh number on flow and heat transfer characteristics are examined at a fixed Prandtl number equal to 1.

In this attempt, nanoparticle enhanced PCM is employed to enhance solidification rate. To augment low thermal conductivity of H2O, CuO nanoparticles were dispersed in it. Also Brownian motion impact was involved in properties of NEPCM. Graphs are obtained via FEM and displayed the impacts of radiation, length of fin and nanoparticles' size. Outputs display that selecting d p  = 40nm leads to the fastest discharging. Discharging time reduces with increase of thermal radiation.

Discharging process of Latent Heat Thermal Energy Storage Systems (LHTESS) containing Phase Change Material (PCM) has been discussed in the present paper. In these systems, thermal energy storage and retrieval occur during solid-liquid phase change. They are used to establish balance between energy supply and demand, but the main restriction for these systems is the weak thermal conductivity of working fluid. In recent years, several enhancement techniques have been employed in order to overcome this problem. In the present study, the method of nanoparticles dispersion in pure PCM to make Nano-Enhanced Phase Change Material (NEPCM) and adding fins with innovative configuration are applied to accelerate solidification process. The abovementioned techniques are analyzed separately. First the geometry parameters of the fin are changed to find the best fin array. Then the effect of nanoparticles volume fraction on solidification rate is studied. The numerical approach in this paper is Standard Galerkin Finite Element Method. In this work, an innovative fin configuration, based on snowflake crystal structure, has been employed to enhance the performance of LHTESS during the discharging process, also the efficiency of nanoparticle dispersion in PCM and adding fin with different structures on LHTESS performance has been examined from the viewpoint of either discharging expedition or maximum energy storage capacity, which are proposed as the novelties here. Results indicate that enhancement of discharging process in LHTESS by applying Snowflake shaped fin structure in comparison with nanoparticle dispersion is higher significantly, although it doesn’t reduce maximum energy storage capacity considerably.

This article is made to examine the impact of external magnetic source on Fe3O4-water ferrofluid convective heat transfer in a porous cavity. The solutions of final equations are obtained by Control volume based finite element method (CVFEM). Graphs are shown for various values of Darcy number (Da), Fe3O4-water volume fraction (ϕ), Rayleigh (Ra) and Hartmann (Ha) numbers. Results indicate that augmenting in Hartmann number results in reduce in velocity of nanofluid and augment the thermal boundary layer thickness. Adding nanoparticles in the based fluid is more effective for higher values of Hartmann number and lower values of Darcy number.

This article delves into the numerical examination of enhancing the productivity of a photovoltaic (PV) system in conjunction with reflectors. In bottom of the traditional PV, thermoelectric generator (TEG) has been used which made from Cu2SnS3 as a sustainable material. A spectral filter, comprising a water-MgO nanofluid, has been applied. To manage the silicon layer's temperature and ensure uniformity, a paraffin layer has been strategically placed at the system's bottom. The paraffin zone incorporates MWCNT nanoparticles mixed with RT25 for improved material properties. To augment conduction, sinusoidal fins have been affixed to the upper wall of the paraffin zone. The simulation involves an unsteady process, validated through comparisons with prior experimental and numerical works. Four distinct cases, considering the use of reflectors and fins, demonstrate their effects on key parameters. Results showcase variations in liquid fraction (LF), temperature of filter at outlet (Tout), paraffin temperature (TPCM), and electrical performance (ηe) over time. As time progresses the temperatures of different layers rise, impacting ηe negatively. The LF and TPCM values increase due to the growing melt phase within the domain. Notably, the impact of fins on ηe diminishes by 62.79 % and 97.3 % in the presence and absence of reflectors, respectively. The integration of fins in the presence of reflectors reduces panel temperatures, improving uniformity by 3.47 %, 0.38 %, and 0.23 % at 1, 2, and 3 h, respectively. This research contributes valuable insights into optimizing PV-TEG system efficiency through the strategic use of reflectors and fins, showcasing their nuanced effects on performance and thermal management.

In this article, water based nanofluid pressure drop and heat transfer augmentation due to using twisted tape insert was investigated. Behaviors of CuO-H2O are predicted according to single phase model. Entropy generation due to fluid friction and heat transfer are presented as contours. Roles of Reynolds number, pitch and height ratios are reported by means of Finite volume method. Formulas for Darcy factor and Nusselt number have been offered. Results demonstrate that better mixing of nanofluid occurs for lower values of pitch ratio. Secondary flow becomes stronger with rise of inlet velocity. Height of turbulator has reverse relationship with thermal boundary layer thickness.

In the current study, Kelvin force as an external source has been used to affect the ferrofluid flow style. The presence of wire below the pipe creates a variable magnetic force that generates rotating eddies near the wire inside the pipe. To augment the cooling rate, the type of operating fluid changes from pure water to Fe3O4-water ferrofluid. Laminar flow was studied with involving homogeneous model for the ferrofluid. A new term was added to momentum equations as Kelvin force due to the gradient of the magnetic field. Impacts of magnetic number (Mn), the fraction of ferrofluid (φ), and Reynolds number (Re) on the configuration of hydrothermal behavior as well as Nusselt number (Nu) and Darcy factor (f) have been investigated. Utilizing ferrofluid can enhance Nu, while the pressure drop augmentation is negligible. So, selecting such kind of ferrofluid is a promising way to gain better performance. Given Re = 50, Nu enhances by about 1.3% with an increase of the concentration of ferrofluid from 0.01 to 0.04. The rise of Re needs greater pumping power as a higher pressure drop will appear in this case. Besides, a thinner boundary layer has been formed with the growth of Re, which offers a higher Nu. When Mn* = 1.57, the growth of Re provides an augmentation of Nu by 39%. With augmenting Kelvin force, the velocity of ferrofluid enhances, which results in a higher pressure drop.

Purpose The purpose of this paper is to research on CuO-water nanofluid Non-Darcy flow because of magnetic field. Porous cavity has circular heat source and filled with nanofluid. Lattice Boltzmann Method (LBM) has been used to simulate this problem. Design/methodology/approach In this research, LBM has been applied as mesoscopic approach to simulate water-based nanofluid free convection. Koo–Kleinstreuer–Li model is used to consider Brownian motion impact on nanofluid properties. Impacts of Rayleigh number, Darcy number, nanofluid volume fraction and Hartmann number on heat transfer treatment are illustrated. Findings It is found that temperature gradient decreases with rise of while it enhances with augment of Ha. Darcy number can enhance the convective flow. Originality/value The originality of this work is to analyze the to investigate magnetic field impact on water based CuO-H 2 O nanofluid natural convection inside a porous cavity with elliptic heat source.

In this article, different shapes of aluminum oxide nanoparticles have been dispersed in to pure H2O to expedite discharging rate in existence of thermal radiation. Galerkin Finite element method is the best tools for time dependent phenomena in a complex geometry such as current enclosure. To calculate nanofluid properties, previous experimental correlations have been employed. Outputs prove that dispersing nanoparticles can expedite the discharging process. Size of nanoparticles has optimum value in which maximum performance can be observed. Considering radiation term can enhance the discharging rate. Impact of amplitude of inner cylinder is more effective in presence of thermal radiation.

Impact of shape factor on nanofluid forced convection is examined considering the impact of Lorentz forces. Brownian motion effect on nanofluid properties is taken into consideration. Vorticity stream function formulation is utilized. The solutions of final equations are obtained by CVFEM. Graphs are shown for various values of Darcy number ( D a ) , CuO – water volume fraction ( ϕ ) , Reynolds ( R a ) and Hartmann ( H a ) numbers. Results prove that temperature gradient augments with rise of Darcy and Reynolds number while it decreases with increase of Lorentz forces. Selecting Platelet shaped nanoparticles results the greatest heat transfer rate.

No abstract is provided for this article.

CuO-water nanofluid MHD convective flow in a porous cavity is studied. Darcy and KKL models are considered for porous media and nanofluid, respectively. The solutions of final equations are obtained by CVFEM. Effective parameters are major axis of elliptic cylinder, CuO-water volume fraction, eccentricity, Hartmann and Rayleigh numbers for porous medium. A correlation for Nuave is presented. Results depicted that heat transfer improvement enhances with rise of buoyancy forces and major axis of elliptic cylinder. Influence of adding nanoparticle augments with augment of Lorentz forces. Increasing eccentricity and Hartmann number leads to reduce Nusselt number.

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Effect of typical and perforated discontinuous helical turbulators on flow and heat transfer in an air to water double pipe heat exchanger is experimentally studied. Experimental analysis is conducted for different values of open area ratio (0–0.0625), Reynolds number (6000–12,000) and pitch ratio (1.83–5.83). According to experimental data, correlations for Nusselt number, friction factor and thermal performance are presented as functions of variable parameters. Non-dominated Sorting Genetic Algorithm II (NSGA II) is applied to find the optimal designs of high efficiency heat exchanger. Pareto front is presented as set of multiple optimum solutions. Results show that friction factor and Nusselt number reduce with rise of open area ratio and pitch ratio. Thermal performance is an increasing function of open area ratio while it is a decreasing function of pitch ratio.

In this paper, the effect of non-uniform magnetic field on nanofluid forced convection heat transfer in a lid driven semi-annulus is studied. The effects of Brownian motion and thermophoresis are taken into account. Control volume based finite element method is used to solve the governing equations in the form of stream function–vorticity formulation. The calculations were performed for different governing parameters namely; the Reynolds number, Lewis number, and Hartmann number. Results show that the Nusselt number has a direct relationship with the Reynolds number while it has a reverse relationship with the Hartmann number and Lewis number.