• Energy Research

AbstractInfluence of adding CuO nanoparticles in the base fluid on flow and heat transfer in an inclined half-annulus was studied considering constant heat flux as boundary condition of hot wall. Control Volume based Finite Element Method (CVFEM) is applied in order to simulate procedure. Pressure gradient source terms are eliminated by using vorticity stream function formulation. Influences of CuO volume fraction, inclination angle and Rayleigh number on hydrothermal manners are presented. Results indicate that inclination angle makes changes in flow style. The strength of eddies reaches to its minimum value when the upper wall is hot. Temperature gradient enhances with rise of buoyancy forces while it reduces with augment of inclination angle.

Abstract Forced convective turbulent hydrothermal analysis in a double pipe heat exchanger is presented experimentally. Perforated turbulators have been utilized in annulus region. Hot water makes the cold air in outer tube warmer. Various amounts of pitch ratio, open area ratio and Reynolds number are considered. Correlations for Nusselt number, thermal performance and Darcy friction factor are examined. NSGA II is utilized to optimize the design. Physical phenomena are shown by means of FVM. Results reveal that thermal performance enhances with augment of open area ratio. Temperature gradient reduces with augment of pitch ratio. The maximum value of thermal performance obtained at η = 1.59 which is occurred for Re = 6000 , λ = 0.07 , PR = 1.06 .

Abstract In this study, two phase simulation of nanofluid flow and heat transfer between parallel plates is investigated. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are solved via homotopy perturbation method. According to comparison with previous works, this method has good accuracy to solve this problem. The semi analytical investigation is carried out for different governing parameters namely; the squeeze number, Hartmann number, Schmidt number and Eckert number. The results indicate that absolute skin friction coefficient decreases with increase of Hartmann number and squeeze number. Also it can be found that that Nusselt number is an increasing function of Hartmann number, Eckert number and Schmidt number but it is a decreasing function of squeeze number.

Abstract 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.

New numerical approach has been selected for simulating magnetic force and radiation influences on alumina transportation within a permeable medium. To enhance characteristics of working fluid, we choose Al2O3–water with various shapes of nanoparticles. Various amounts of radiation, magnetic force and buoyancy have been considered to show their impacts on nanoparticles transportation. Brownian motion influences on working fluid thermal conductivity and viscosity were involved. Outcomes prove that convection decreases with augment of magnetic forces. Considering radiation can increase Nusselt number.

Abstract Nanofluid flow and heat transfer in a rotating system is studied numerically using fourth-order Runge–Kutta method. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The numerical investigation is carried out for different governing parameters namely: Reynolds number, Rotation parameter, injection parameter, Schmidt number, Thermophoretic parameter and Brownian parameter. The results indicate that skin friction parameter increases with augment of Reynolds number and Rotation parameter but it decreases with increase of injection parameter. Also it can be found that Nusselt number has a direct relationship with Reynolds number and injection parameter while it has a reverse relationship with Rotation parameter, Schmidt number, Thermophoretic parameter and Brownian parameter.

Abstract 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 dp = 40 nm leads to the fastest discharging. Discharging time reduces with increase of thermal radiation.

Abstract In this paper, effect of magnetic field on free convection heat transfer in an enclosure filled with nanofluid is studied. KKL (Koo-Kleinstreuer-Li) correlation is used for simulating effective thermal conductivity and viscosity of nanofluid. The inner cylinder is maintained at uniform heat flux and the outer cylinder has constant temperature. The governing equations are solved via Control Volume based Finite Element Method. 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, volume fraction of nanoparticle, Rayleigh number and aspect ratio on streamline, isotherm and heatline are examined. The results show that as Hartmann number increases Nusselt number decreases while opposite trend is observed as nanoparticles volume fraction, Rayleigh number and aspect ratio increase. Domination of conduction mechanism causes heat transfer enhancement to increase. So enhancement in heat transfer increases with increase of Hartmann number and aspect ratio while it decreases with augment of Rayleigh number.

Abstract In this paper, the forced convective heat transfer of water-Fe 3 O 4 nanofluid in an enclosure with moving and sinusoidal walls is investigated. New numerical method is chosen namely CVFEM. Influences of Reynolds, Hartmann numbers and volume fraction of Fe 3 O 4 on hydrothermal characteristics are presented. Results indicated that temperature gradient is an enhancing function of lid velocity and volume fraction of Fe 3 O 4 but it is a reducing function of Lorentz forces. Besides, heat transfer improvement augments with enhance of Reynolds number but it reduces with augment of Hartmann number.

Abstract A numerical analysis of Copper oxide-H2O nanomaterial hydrothermal characteristics through a duct with utilizing turbulator under constant heat flux has been carried out by means of FVM. Simulations contain the effect of width tape (b) and Reynolds number (Re). Single phase model for nanomaterial and k-ɛ for turbulence modeling have been selected. Outputs indicate that friction factor tends to decline with augment of Re. Greater Nu due to insertion of turbulator is related to swirl flow generation. Augmented convective heat transfer is obtained with inserting turbulator with higher width.