The aim of the present paper is to study the flow of nanofluid and heat transfer characteristics between two horizontal plates in a rotating system. The lower plate is a stretching sheet and the upper one is a solid porous plate. Copper (Cu) as nanoparticle and water as its base fluid have been considered. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved analytically using the homotopy analysis method (HAM). Comparison between HAM and numerical solutions results showed an excellent agreement. The results for the flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, suction/injection parameter, rotation parameter, and Reynolds number. It is shown that the inclusion of a nanoparticle into the base fluid of this problem is capable of causing change in the flow pattern. It is found that for both suction and injection, the heat transfer rate at the surface increases with increasing the nanoparticle volume fraction, Reynolds number, and injection/suction parameter and it decreases with power of rotation parameter.
No abstract is provided for this article.
The application of the control volume finite element method (CVFEM) for magnetohydrodynamic and ferrohydrodynamic effects on natural, forced, and mixed convective heat transfer are studied in this chapter. The basic idea and implementation of source terms and boundary conditions are presented. Also, sample codes of CVFEM for two-dimensional pure diffusion and advection diffusion are provided. After validation of the present code, several examples are provided in which CVFEM is used to simulate nanofluid flow and heat transfer in the presence of a magnetic field.
No abstract is provided for this article.
Influence of external magnetic source on free convection of ferrofluid is reported in this paper. Obtaining systems have been solved through Control volume based finite element method. Influences of Rayleigh, Hartmann numbers, size of inner cylinder and volume fraction of Fe3O4 on hydrothermal characteristics are presented. Results indicate that both temperature gradient and nanofluid velocity decease with augment of Hartmann number. Thermal boundary layer thickness reduces with augment of r in . Nusselt number decreases with rise of Lorentz forces while it enhances with rise of buoyancy forces.
Heat recovery is one of the solutions to reduce Carbon dioxide emission, and using latent heat thermal energy storage systems (LHTESS) can be a promising way for heat recovery. In the present article, for the first time, the effects of both inorganic nanoparticles as an additive to PCM (phase change materials) and magnetic field on the PCM solidification rate inside a porous energy storage system have been modeled. For this purpose, the mixture of CuO nanoparticles and water was used as NEPCM (nanoparticle-enhanced PCM), and an external magnetic field was applied to the system. The unsteady process of solidification inside the storage system was simulated by employing finite element method (FEM). The impacts of various parameters including Lorentz forces strength, CuO/water concentration, and Rayleigh number on the charging time have been evaluated. Solid fraction, temperature, and streamline contours have been plotted to study the solidification process locally. The results indicated that with augmenting the Hartmann number from 0 to 10, the solidification time was reduced up to 23.5% in average. On the other hand, the addition of nanoparticles to PCM with volume fractions up to 4% leads to, on average, a 14% decrease in the solidification time. The obtained results suggest to employ the magnetic field as an effective solution to accelerate the solidification in energy storage systems while to reinforce the influence of magnetic field; nanoparticles can be added to the PCM. Finally, the solidification time was correlated with three main design parameters, i.e. nanoparticle volume fraction, Hartmann and Rayleigh numbers with a mathematical expression.
No abstract is provided for this article.
Phase change materials (PCMs) are effective methods for energy utilization and increasing efficiency in various systems, especially solar systems. Phase change materials are used to store energy during the day and recover energy at night when the sun is not present. The main weakness of some of these materials is their poor thermal conductivity, which is increased by adding nanoparticles and fins while also accelerating the melting (charging) process. Much research has been done on PCMs. In this chapter, the features, advantages, and disadvantages, methods of integration and increasing the efficiency of PCM, and its types of applications in different systems and for different places in buildings have been examined in a specialized and advanced manner.
Influence of magnetic field on CuO–H2O nanofluid forced convective heat transfer is investigated considering Marangoni convection. Similarity solution is used to obtain the ordinary equations. Runge-Kutta integration scheme is utilized to solve this problem. Influences of Hartmann number and CuO volume fraction on flow and heat transfer characteristics are presented. Results indicate that rate of heat transfer is an augmenting function of CuO volume fraction. Influence of CuO volume fraction on normal velocity is higher than tangential velocity. Nusselt number has reverse relationship with magnetic number.
This investigation reports the magnetic field effect on natural convection heat transfer in a curved-shape enclosure. The numerical investigation is carried out using the control volume-based-finite element method (CVFEM). The numerical investigations are performed for various values of Hartmann number and Rayleigh number. The obtained results are depicted in terms of streamlines and isotherms which show the significant effects of Hartmann number on the fluid flow and temperature distribution inside the enclosure. Also, it was found that the Nusselt number decreases with an increase in the Hartmann number.
This study discusses an evacuated tube collector-type solar water heater (ETCSWH) using a phase change material (PCM) chamber with fins, nanofluid, and nano-enhanced phase change material (NEPCM). First, the charging phenomena in a horizontal triplex tube heat exchanger (TTHX) equipped with fins, natural convection, and an ETCSWH system without PCM is simulated to validate the solution. The impact of adding fins and nanoparticles with a volume fraction of 3% of Al 2 O 3 and Cu to paraffin wax and water-based fluid, respectively, on the unit's efficiency has been examined. The proposed system for the PCM melting process, heat storage, fluid flow behavior in the system, and velocity distribution and temperature contour in the storage tank and three parts of the absorber tube have been evaluated using ANSYS FLUENT software in a three-dimensional and transient simulation. The results show that Case 8 has improved by 39.7% compared to Case 1 and Case 4 by 5.2% compared to Case 1 within 4 h of the melting process. Also, Case 8 with a 43% and 6.4% shorter melting time than Cases 1 and 5 has the best performance and the greatest heat transfer rate. The productivity of the ETCSWH system is considerably enhanced by the use of fins, NEPCM, and nanofluid.
In this simulation, CuO-H2O nanofluid flow due to Lorentz forces in a permeable channel has been reported via Lattice Boltzmann method. Homogeneous model is considered for nanofluid in which Brownian motion influence is taken into account. Isotherms and streamlines are depicted for various values of effective parameters such as CuO nanoparticles volume fraction, Reynolds number, Darcy number and Hartmann number. Results indicate that heat transfer rate enhances with increase of permeability of porous medium. Similar behavior is reported for Reynolds number. Temperature boundary layer thickness increases in existence of magnetic field.
Magnetohydrodynamic nanofluid forced convective heat transfer is investigated considering Marangoni convection. A two-phase model is selected for modeling of a nanofluid. The Runge-Kutta integration scheme is utilized to solve this problem. Influences of the Marangoni ratio, Schmidt number, Brownian motion parameter, magnetic number and thermophoretic parameter on the hydrothermal characteristics are presented. Results depict that the temperature augments with increases of the Schmidt number, Brownian motion, magnetic number and the thermophoretic parameters but it reduces with the rise of the Marangoni ratio. As the Marangoni ratio augments, the hydraulic boundary layer thickness enhances.
This study is applied Lattice Boltzmann Method to investigate the natural convection flow utilizing nanofluids in a concentric annulus. A numerical strategy presents for dealing with curved boundaries of second order accuracy for both velocity and temperature fields. The fluid between the cylinders is a water-based nanofluid containing different types of nanoparticles: copper (Cu), alumina (Al2O3), titanium oxide (TiO2) and silver (Ag). The nanofluid is a two component mixture modeled as a single-phase incompressible fluid with the different thermophysical properties. This investigation compared with other experimental and found to be in excellent agreement. Result shows The type of nanofluid is a key factor for heat transfer enhancement. In this study the highest values of percentage of heat transfer enhancement are obtained when using silver nanoparticle.
In current investigation, a clean energy storage unit has been designed aiming to decrease the energy consumption through the building. To increase the space between the passing air and the Phase change material (PCM), instead of a smooth channel, a sinusoidal channel has been considered for the airway passage. Furthermore, porous media and nanoparticles have been applied in this unit for the purpose of enhancing heat transfer. Considering previous research works, the simultaneous use of these three methods for augmenting the performance has not been scrutinized so far. In this study, three mechanisms for augmenting heat transfer and the interaction of these methods to augment the performance of the system have been evaluated. Based on comparison with experimental data, outputs are very excellent fit with maximum 9.3% deviation. For evaluate efficiency of unit, solidification duration was analyzed and outputs proved that for case with porous foam solidification finishes 21.4% faster than the base case. Slope of profile for second case is higher than first one and the process completed at t = 33 h. For case with porous foam, augmenting time up to 13 h leads to augmenting trend for heat release value and then opposite trend appears. Heat flux transfer to air reduces with rise of time which provides lower temperature of outlet air. Slope of profile for air outlet temperature augments at t = 33 h when all liquid convert to solid for second case. As porous foam utilizes, temperature of PCM reduces and no sensible difference appears in various positions in each section.
