In the current study, an evacuated solar collector with sinusoidal U-pipes filled with paraffin was investigated for energy saving. To generate electricity in addition to storing thermal energy, thermoelectric generator (TEG) was integrated into the unit. The paraffin was enhanced with hybrid nanoparticles composed of silver (Ag) and titanium dioxide (TiO2) to improve thermal conductivity. Additionally, innovative fin shapes were employed to accelerate the melting process, and various fin arrangements were tested. A numerical technique was utilized to model the process, and the outputs showed good agreement with previous study, confirming the accuracy of the simulations. The study aimed to identify the optimal geometry for the solar energy system. The best-performing configuration included two sinusoidal U-pipes and four inclined fins, in contrast to the base case, which featured circular U-pipes without fins. For the optimal geometry, the liquid fraction (LF) and paraffin temperature (TPCM) increased by 47.38 % and 1.16 %, respectively, over time. At 45 min, with all enhancements applied, LF and TPCM improvements reached 52.21 % and 2.63 %, respectively. The integration of the TEG module allowed the system to produce electricity while storing thermal energy, although the efficiency of the TEG decreased by about 3.5 % due to the modifications. The modified solar system achieved an electrical output of 7.15 kW. By integrating sinusoidal U-pipes, hybrid nanoparticles, and novel fin designs, the study significantly improves thermal energy storage and electricity generation.
Magnetohydrodynamic CuO-water nanofluid flow in a porous semi annulus with constant heat flux is studied by means of Control Volume based Finite Element Method. Koo-Kleinstreuer-Li correlation and Darcy model are applied for nanofluid and porous media, respectively. Effective parameters are radius of inner cylinder, CuO-water volume fraction, Hartmann and Rayleigh numbers for porous medium. A formula for Nuave is presented. Results revealed that heat transfer augmentation decreases with rise of buoyancy forces. Influence of adding nanoparticle augments with increase of Lorentz forces. Increasing Hartmann number leads to a reduction in temperature gradient.
In this paper nanofluid flow and heat transfer characteristics between two horizontal parallel plates in a rotating system are investigated. The effective thermal conductivity and viscosity of the nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model the effect of Brownian motion on the effective thermal conductivity is considered. The basic partial differential equations are reduced to ordinary differential equations which are solved numerically using the fourth-order Runge–Kutta method. Comparison between the obtained results and previous works are well in agreement. Results show that the magnitude of the skin friction coefficient is an increasing function of the magnetic parameter, rotation parameter and Reynolds number and it is a decreasing function of the nanoparticle volume fraction. The Nusselt number increases with increase of nanoparticle volume fraction and Reynolds number but it decreases with increase of Eckert number, magnetic and rotation parameters.
This study investigates a comprehensive enhancement strategy for photovoltaic (PV) panel efficiency, focusing on increasing electrical output through the integration of parabolic reflectors, advanced cooling mechanisms, and thermoelectric generation. Parabolic reflectors are implemented in the system to maximize solar irradiance on the PV panel's surface, while a specialized cooling system is introduced to regulate temperature distribution across the silicon layer. This cooling system consists of a finned duct filled with paraffin (RT35HC) and enhanced with SWCNT nanoparticles, which improve the thermal properties of the paraffin, facilitating more effective heat dissipation. The PV module is also integrated with a TEG (thermoelectric generator) to capture excess thermal energy and convert it into additional electrical power, allowing for a more efficient overall system. To simulate the heat flux introduced by the reflectors, SolTrace software was employed, while the unsteady, three-dimensional thermal behavior of the system was analyzed using ANSYS FLUENT. Simulated results demonstrated that, with the cooling system in place, the PV efficiency (ηel, PV) improves by approximately 16.46% in clean conditions. However, dust accumulation on the panel significantly impacts performance, reducing ηel, PV by around 46.48% after 60 min. The inclusion of fin structures further optimizes the system, boosting overall efficiency by approximately 6.77% in clean conditions and 3.78% under dust-affected conditions. Additionally, thermal efficiency for the clean state increased by about 8.47% due to the fins. Notably, the combined effects of parabolic reflectors, fin-enhanced cooling, and TEG integration yield an electrical output power approximately 2.94 times greater than that of a PV panel without any reflector or cooling modifications.
In this paper, Optimal Homotopy Asymptotic Method (OHAM) is combined with Galerkin method to investigate the MHD Jeffery-Hamel flows in non-parallel walls for strongly nonlinear ordinary differential equations. Results for velocity profiles in divergent and convergent channels for various values of Hartmann and Reynolds numbers are compared with numerical method (the Runge-Kutta method of order 4). The results confirm the notion that the OHAM method is a powerful and efficient technique for finding exact solutions for differential equations which have great significance in different fields of science and engineering. Also, it can be found that increasing Hartmann number will lead to backflow reduction.
Magnetic nanofluid (ferrofluid) is a magnetic colloidal suspension consisting of base liquid and magnetic nanoparticles with a size range of 5–15 nm in diameter coated with a surfactant layer. The effect of magnetic field on fluids is worth investigating due to its numerous applications in a wide range of fields. The study of interaction of the magnetic field or the electromagnetic field with fluids have been documented, for example, among nuclear fusion, chemical engineering, medicine, and transformer cooling. The goal of nanofluid is to achieve the highest possible thermal properties at the smallest possible concentrations by uniform dispersion and stable suspension of nanoparticles in host fluids. In this chapter, the influence of external magnetic field on ferrofluid flow and heat transfer is investigated. The effects of both ferrohydrodynamic and magnetohydrodynamic have been taken in to account. So, the effects of Lorentz and Kelvin forces on hydrothermal behavior are examined.
In this study Control Volume based Finite Element Method is applied to solve the problem of natural convection heat transfer in an enclosure filled with nanofluid. The important effect of Brownian motion and thermophoresis has been included in the model of nanofluid. The inner sinusoidal and outer circular walls are maintained at constant temperatures while the two other walls are thermally insulated. The heat transfer between cold and hot regions of the enclosure cannot be well understood by using isotherm patterns so heatline visualization technique is used to find the direction and intensity of heat transfer in a domain. Effects of thermal Rayleigh number (Ra), buoyancy ratio number (Nr) and Lewis number (Le) on streamline, isotherm, isoconcentration and heatline are examined. The results indicate that the average Nusselt number decreases as buoyancy ratio number increases until it reaches a minimum value and then starts increasing. As Lewis number increases, this minimum value occurs at higher buoyancy ratio number.
In this study MHD effect on natural convection heat transfer in an enclosure filled with nanofluid is investigated. The transport equations used in the analysis took into account the effect of Brownian motion and thermophoresis parameters. The Navier Stokes equations in their vorticity-stream function form are used to simulate the flow pattern, isotherms and concentration. The governing equations are solved via Control Volume based Finite Element Method. The inner and outer circular walls are maintained at constant temperatures while two other walls are thermally insulated. The heat transfer between cold and hot regions of the enclosure cannot be well understood by using isotherm patterns so heatline visualization technique is used to find the direction and intensity of heat transfer in a domain. Effect of Hartmann number (Ha =0,30,60 and 100), buoyancy ratio number (Nr =0.1–4) and Lewis number (Le =2,4,6 and 8) on streamline, isotherm, isoconcentration and heatline are examined. Also a correlation for Nusselt number corresponding to active parameters is presented. The results indicate that Nusselt number is an increasing function of buoyancy ratio number but it is a decreasing function of Lewis number and Hartmann number. Also it can be concluded that as buoyancy ratio number increases the effects of other active parameters are more pronounced.
The present study investigates heat transfer of nanofluid flow in micro channel heat sink (MCHS) in the presence of a magnetic field. Al2O3-water nanofluid is chosen the best among other nanolfluid and is used as a coolant fluid in solution. The KKL correlation is utilized for calculation of the effective thermal conductivity and viscosity of nanofluid. Modified Darcy equation is applied for porous medium and the two-equation model with thermal dispersion is employed for heat transfer between fluid and solid sections. Since the coupled heat transfer equations of nanofluid and solid phase are nonlinear, the analytical Collocation method (CM) is employed to solve this problem. Effects of the Hartmann number, nanoparticles volume fraction, nanoparticle diameter, porosity, channel aspect ratio on temperature distribution, velocity and Nusselt number are investigated deliberately. Results show that Nusselt number has direct relationship with applying a magnetic field on MCHS.
Nanofluid flow between two circular cylinders is studied in existence of magnetic field. KKL model is applied for nanofluid. Thermal radiation effect has been considered in energy equation. AGM is selected for solving ODEs. Semi analytical procedures are examined for various active parameters namely; aspect ratio, Hartmann number, Eckert number and Reynolds number. Results indicate that temperature gradient enhances with rise of Ha, Ec and η but it reduces with augment of Re. Velocity reduces with rise of Lorentz forces but it augments with rise of Reynolds number.
In this research, natural convection of a non-Newtonian copper-water nanofluid between two infinite parallel vertical flat plates is investigated. The basic partial differential equations are reduced to ordinary differential equations which are solved analytically using the differential transformation method. The results obtained using the differential transformation method and those from a numerical method are in good agreement which demonstrates the ability of the differential transformation method to solve such problems. It is shown that as the nanoparticle volume fraction increases, the momentum boundary layer thickness increases, whereas the thermal boundary layer thickness decreases.
In this research, entropy generation and forced convection heat transfer of Al2O3-water nanofluid in a heat exchanger equipped with helical twisted tape is investigated via Finite volume method. Influences of height ratio (BR), pitch ratio(PR) and Reynolds number (Re) on nanofluid entropy generation are reported. Suitable formula for entropy generation is provided. Results reveal that thermal entropy generation decreases with rise of BR and Re. Frictional entropy generation augments with rise of height ratio.
In this study, the effects of magnetic field on nanofluid flow, heat, and mass transfer between two horizontal coaxial cylinders are studied using a two-phase model. The effect of viscous dissipation is also taken into account. By using the appropriate transformation for the velocity, temperature, and concentration, the basic equations governing the flow, heat, and mass transfer are reduced to a set of ordinary differential equations. These equations subject to the associated boundary conditions are solved numerically using the fourth-order Runge-Kutta method. The effects of Hartmann number, Reynolds number, Schmidt number, Brownian parameter, thermophoresis parameter, Eckert number, and aspect ratio on flow, heat, and mass transfer are examined. Results show that the Nusselt number has a direct relationship with the aspect ratio and Hartmann number but it has a reverse relationship with the Reynolds number, Schmidt number, Brownian parameter, thermophoresis parameter, and Eckert number.
In this article, simulations are performed to explore the feasibility of utilizing nanoparticle and sinusoidal cold inner cylinder to decrease time of solidification. Storage tank is full of NEPCM (CuO–water). The focus of current modeling is on the impacts of shape of cold wall and concentration of NEPCM on discharging rate. Simulation of the transient process was carried out employing FEM based Galerkin method. Decreasing amplitude of inner wall results in prolonging solidification while increasing N, results opposite outcome. Propagation rate of solid fraction enhances with augment of volume fraction of NEPCM.
