393 publications from this institution
Phase change material (PCM) provides an effective solution for energy conservation in air conditioning. The significance of thermal comfort in people's lives has led to an increase in energy consumption for air conditioning. This increase is due to factors such as extreme weather conditions, population growth, and higher living standards. Consequently, incorporating thermal energy storage technology that is based on PCMs with space heating and cooling systems has gained growing interest to achieve significant energy savings. The use of PCMs to improve building energy performance has gained considerable attention in recent years to address the increasing resource scarcity and environmental degradation. This chapter examines the optimization of the building envelope by integrating PCMs into surrounding walls, roofs, and floors. It also explores the use of building equipment optimized with PCMs to reduce energy consumption. Thermal energy storage for cooling applications is a promising technology for reducing energy consumption by storing cold in PCMs. These materials can store a significant amount of cold and undergo phase change at a constant temperature, thereby improving thermal comfort. This chapter aims to investigate the use of PCMs in cooling systems, their relationship with buildings, their potential for reducing energy consumption, and their impact on indoor temperatures and air quality.
Most scientific problems in solid mechanics are inherently nonlinear by nature, and, except for a limited number of cases, most of them do not have analytical solutions. The most nonlinear problems in solid mechanics are vibration analysis; deflection and deformation of different beams, materials, or plates. In this chapter some of these problems are presented and solved by DTM, which is categorized in the following sections: 8.1 Introduction 8.2 Deflection Prediction of a Cantilever Beam 8.3 Vibration Analysis of Stepped FGM Beams 8.4 Piezoelectric Modal Sensors for Cantilever Beams 8.5 Damped System With High Nonlinearity 8.6 Free Vibration of a Centrifugally Stiffened Beam 8.7 Deflections of Orthotropic Rectangular Plate 8.8 Free Vibration of Circular Plates 8.9 Vibration of Pipes Conveying Fluid 8.10 Piezoelectric Modal Sensor for Nonuniform Euler–Bernoulli Beams With Rectangular Cross Section 8.11 Free Vibrations of Oscillators 8.12 Composite Sandwich Beams With Viscoelastic Core
In this paper, free convection of ferrofluid in a cavity heated from below in presence of external magnetic field is studied numerically using the Lattice Boltzmann method. The enclosure is filled with a mixture of kerosene–cobalt. This investigation was compared with other experimental and numerical works and found to be in excellent agreement. Effects of Rayleigh number, magnetic coefficient, heat source length and volume fraction of cobalt on flow and heat transfer characteristics are examined. Results show that particles with a smaller size have better ability to dissipate heat, and a larger volume fraction would provide a stronger driving force which leads to increase in temperature profile. The Nusselt number has direct relationship with the Rayleigh number and heat source length while it has reverse relationship with size of nanoparticle and volume fraction of cobalt.
No abstract is provided for this article.
This article introduces an innovative integration of a thermoelectric generator (TEG) module with a U-tube evacuated solar system, using paraffin as the phase change material (PCM). To enhance the PCM's melting rate and improve the system’s overall thermal efficiency, three advanced strategies were employed: (1) The addition of ternary nanoparticles—comprising MgO, ZnO, and MWCNT—into the paraffin to boost thermal conductivity; (2) Modification of the U-tube's geometry from a circular to a three-lobed design for improved heat transfer; and (3) The installation of tree-shaped fins to optimize heat distribution and accelerate the melting rate. The unsteady thermal behavior has been modeled using the finite volume method. The results demonstrated that these techniques significantly increased the melting rate and thermal efficiency, though they led to a slight decrease in the TEG's electrical power output. Four configurations were examined: (Case 1: Circular U-tube with pure paraffin; Case 2: Three-lobed U-tube with pure paraffin; Case 3: Three-lobed U-tube with ternary nanofluid; Case 4: Three-lobed U-tube with ternary nanofluid and tree-shaped fins). The incorporation of ternary nanoparticles accelerated the melting process, increasing the charging rate by 3.47 % at 150 s and 1.92 % at 450 s. Replacing the circular U-tube with a three-lobed design, combined with ternary nanomaterials, improved the liquid fraction by 57.76 % at 150 s and 22.28 % at 450 s. When all three techniques were applied together, the temperature of the system rose by 6.14 % at 150 s and 4.57 % at 450 s. However, in case 4, a decrease of 3.23 % in the TEG’s efficiency was observed at 900 s, yielding an electrical output of 2.28 kW.
Influence of external magnetic source on ferrofluid convection in an enclosure with elliptic hot cylinder is studied. Governing formulae are first made dimensionless form along with the associated boundary conditions and then solved by powerful numerical method namely CVFEM. Influences of Rayleigh and Hartmann numbers and Fe3O4 volume fraction on hydrothermal behavior are presented. Results indicated that temperature gradient is an enhancing function of volume fraction of Fe3O4 and Rayleigh number but it is a reducing function of Lorentz forces. Lorentz forces cause the nanofluid velocity to reduce and augment the thermal boundary layer thickness. The role of effective parameters is illustrated through graphs and tables. Comparison of the present work is also made with the existing literature.
The theme of current research is to explore the impact of entropy generation on mixed convective flow of micropolar fluid containing water-based TiO2 nanomaterial toward a vertical surface in a non-Darcy porous medium. The results are confined for opposing and assisting flows. Similarity equations are achieved and then worked out numerically by the Keller box technique. The impacts of substantial parameters on temperature distribution, velocity profile, and microrotation velocity, together with the Nusselt number and the skin friction, are illustrated with the help of graphs. Two solutions are achieved in opposing flow while the solution is unique in assisting flow. It is also observed that the separation of boundary layer accelerates due to volume fraction and delays due to micropolar parameter.
In this study, natural convection heat transfer in an L-shaped enclosure filled with a nanofluid is studied. The numerical investigation is carried out using Control Volume based Finite Element Method (CVFEM). The important effects of Brownian motion and thermophoresis have been included in the model of the nanofluid. Comparisons with previously published works are conducted and the results are found to be in good agreement. The influence of pertinent parameters such as the Lewis number, aspect ratio, thermal Rayleigh number and the concentration Rayleigh number on the flow, heat transfer and Nusselt number are illustrated graphically and discussed. Results show that the Nusselt number increases with increases in either of the thermal Rayleigh number and the Lewis number but it decreases with increases in either of the aspect ratio and the concentration Rayleigh number.
Present study analyzes the issue of entropy generation of water with Al2O3 nanoparticles in a horizontal porous microchannel heated symmetrically. 2D distribution of temperature in both phases are derived using two-energy-equation model. An analytic investigation is carried out and the parameters of magnetohydrodynamic (MHD) field, solid heat generation and symmetric thermal condition are explored thoroughly. The results revealed that the MHD field noticeably affects the distribution of temperature and velocity and as an output the heat transfer irreversibilities during the process. The solid and fluid heat transfer irreversibilities for the case under MHD field are lower than those of the case without it, which proves the advantages to MHD field in declining the heat transfer irreversibility. Then, it was obtained that when Ha number is constant and Reynolds number has the optimum value of 6.5, total entropy generation is minimum and it decreases when MHD is intensified at Re op . Also MHD was effective merely when the value of Reynolds number was lower than the critical value. By applying heat generation to the solid, for the MHD cases, no significant changes were observed in MHD irreversibility, however, entropy generation of the solid was achieved to be the most effective parameter and the value of total irreversibility increased noticeably. The analysis of thermal equilibrium and non-equilibrium models and the differences in irreversibilites showed that the increments in suspension of nanoparticles reduced the deviation between the two models, and intensification of Ha number at low biot numbers further reduces it.
Purpose The purpose of this paper is to analyze hydromagnetic flow between two horizontal plates in a rotating system. The bottom plate is a stretching sheet and the top one is a solid porous plate. Heat transfer in an electrically conducting fluid bounded by two parallel plates is also studied in the presence of viscous dissipation. Design/methodology/approach Differential Transformation Method (DTM) is used to obtain a complete analytic solution for the velocity and temperature fields and the effects of different governing parameters on these fields are discussed through the graphs. Findings The obtained results showed that by adding a magnetic field to this system, transverse velocity component reduces between the two plates. Also as the Prandtl number increases, in presence of viscous dissipation, the temperature between the two plates enhances while an opposite behavior is observed when the viscous dissipation is negligible. Originality/value The equations of conservation of mass, momentum and energy are reduced to a non‐linear ordinary differential equations system. Differential Transformation Method is utilized to approximate the solution for velocity and temperature profiles.
No abstract is provided for this article.
In this article, numerical studies are done to examine the effects of non-uniform magnetic field on the heat transfer of ferrofluid inside 90° elbow channel. In order to simulate the flow inside the domain, the finite volume method with the SIMPLEC algorithm is applied to reveal the effects of non-uniform magnetic field on the thermal and friction factor of ferrofluid. The ferrofluid inside elbow is assumed single phase and laminar and constant heat flux is applied on the wall while a single wire is chosen as a source of non-uniform magnetic field in the center of the elbow. The effects of magnetic field on the flow feature and temperature distribution in the vicinity of magnetic source are comprehensively explained. Comprehensive parametric studies are done to study the influence of various factors such as intensity of magnetic field and Reynolds number on the heat transfer. Obtained results demonstrated that the average Nusselt number of ferrofluid increases more than 28.6% as the magnetic field with strength of Mn = 9.32 × 10 6 is applied in the vicinity of the elbow. Furthermore, heat transfer augments approximately 18% as the Reynolds number inside the elbow is increased from 50 to 100.
Purpose The purpose of this paper is to examine the effect of magnetic field on ferrofluid convective mode with radiation. Design/methodology/approach Viscosity of Fe3O4 ferrofluid is considered as a function of magnetic field. Solutions of the governing equations are obtained by a powerful numerical method, namely, control volume finite element method (CVFEM). Roles of radiation parameter (Rd), number of undulations (N), Fe3O4–water volume fraction (ϕ), Hartmann (Ha) and Rayleigh numbers are illustrated graphically. A correlation for Nuave is extracted. Findings The inner wall temperature decreases with increasing buoyancy forces, but increases with increasing Rd and Ha. Also increasing Rd results in increasing nanofluid motion. This influence is more evident when convection flow is dominant. As nanofluid temperature increases, the nanofluid begins moving from the warm surface to the outer one and dropping along the circular cylinder. At low Rayleigh number, conduction is more significant than convection. |Ψmax| increases as buoyancy force increases and it decreases as the Lorentz force increases. As Hartmann number increases, the center of the vortices moves to x = 0. As Ra increases, convection becomes stronger. Thus, |Ψmax| and temperature gradient increase with increasing Ra. As N increases, the distortion of isotherms reduces and vortices become weaker. Increasing Hartmann number results in a reduction in the thermal plume and the heat transfer mechanism changes from convection to conduction. Nusselt number decreases with increasing N ⋅ Nu decreases with increasing Lorentz force. At N = 5 , increasing the Lorentz force causes the main vortices to convert into three smaller ones. As the Lorentz force increases, the two upper vortices merge together and the thermal plume vanishes. The number of extrema in the Nuloc profile matches the existence of the thermal plume and the number of undulations. Nuave increases with increasing Rd. As buoyancy forces increase, the temperature decreases and in turn Nuave increases with increasing Ra. Originality/value Nanofluids are an innovative way to enhance radiation heat. In this paper, MHD Fe3O4–water nanofluid natural convection with radiation source term is examined. Magnetic field-dependent (MFD) viscosity is considered. Using the CVFEM, numerical simulations are carried out for various values of the radiation parameter (Rd = 0 to 0.8), volume fraction of Fe3O4–water (ϕ = 0 to 0.04), Rayleigh number (Ra = 103, 104 and 105), number of undulations (N = 3,4 and 5) and Hartmann number (Ha = 0 to 40).
This study focuses on new design of a photovoltaic-thermal (PVT) unit through the utilization of a cylindrical reflector. The integration of a thermoelectric generator layer fabricated from Cu2SnS3 (CTS) and a nanofluid spectral filter composed of a MgO-water mixture within PVT leads to performance enhancement. A mathematical approach was established involving optical features and the Finite volume approach was employed for simulation. The validity of the method was verified through comparison with experimental data. By introducing fins and a filter duct, along with a cylindrical reflector, the overall performance is enhanced by 36.3%. Adding a reflector into the finned structure leads to an overall performance improvement of approximately 5.7% and 4.7% with and without a nanofluid filter. By increasing the velocity of the filter, the electrical performance was enhanced resulting in an improvement of 37.7% when a reflector is present. Integrating a reflector, fins and filter in a combined system leads to the maximum reduction in CO2 emission with a value 2 times higher than that of conventional PV.
Influence of non-uniform magnetic field on Fe3O4–water ferrofluid flow in a porous cavity is simulated. Shape factor effect on nanofluid properties is taken into consideration. Vorticity stream function formulation is reported. The solutions of final equations are obtained using CVFEM. Figures are depicted for different values of radiation parameter ( Rd ) , Darcy number ( Da ) , Fe3O4–water volume fraction ( ϕ ) , Rayleigh ( Ra ) and Hartmann ( Ha ) numbers. Results show that augmenting in Hartmann number leads to decrease in velocity of nanofluid and heat transfer rate. Utilizing Platelet shaped nanoparticles results the highest Nusselt number.
