The present investigation concern with the study on exergy loss and turbulent flow inside a round duct equipped with complex turbulator. The Copper oxide/H2O nanofluid at 0.04 particle volume concentration has been considered as carrier fluid. The tests were examined under the turbulent flow with Reynolds ranges of 5000 < Re < 15000. The duct has been conducted under constant heat flux of wall surface. Outputs indicates that flow blockage increases with augment of Re and b. Exergy drop is reversely proportional to the convective mode and therefore X d declines with rise of tape width and Re.
Influence 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.
Influence of external magnetic source in two-dimensional Fe3O4–water nanomaterial is numerically addressed. Numerical solution is carried out using control based volume finite element method (CVFEM). Combined influences of Lorentz and Kelvin forces are taken into account. Vorticity–stream function forms of equations have been considered. Influences of nanofluid volume fraction, Hartmann, Rayleigh and Magnetic numbers on velocity and temperature distribution are examined. Results demonstrate that temperature gradient augments with rise of Kelvin forces while it reduces for Lorentz forces. Moreover, heat transfer augmentation enhances with augment of Lorentz forces.
This work delves into the efficiency of the disturber device on the productivity of a Concentrated Photovoltaic-Thermal (CPV/T) unit. For this purpose, numerical techniques were employed to model the three-dimensional CPV/T system along with a TT (twisted tape) device. Initially, the influence of tube cross-section patterns was investigated. This involves designing three distinct tubes with plain, three-lobed, and five-lobed patterns. The simulation considers PV/T systems with various tubes, both with and without the inclusion of twisted tapes, utilizing H2O as the testing fluid. The research assesses the influence of concentration ratio through varying incident irradiations at 1, 2, and 3 suns. The investigation of the temperature over the silicon layer reveals a substantial decrease in the temperature gradient with the incorporation of a twisted tape insert. The three-lobed tube demonstrated optimal performance for the PV/T module. Consequently, an examination was conducted to assess the efficacy of utilizing Al2O3–H2O nanofluid on the productivity of the system. Using the optimal insert pattern under 3 suns has been determined to improve thermal and electrical performances by 5.1 % and 4.2 %. A thermohydraulic analysis is implemented to measure the thermal improvement brought about by various configurations. The results demonstrated that the inserts have the potential to elevate this factor above unity. Additionally, an environmental evaluation of the presented configurations includes an analysis of two key parameters: emission reduction and saved carbon credits. The findings demonstrated that employing the CPV/T system under 3 suns with the optimal design leads to a reduction of approximately 5541 kg of carbon emissions over 10 years, resulting in a savings of about $80.3 in carbon credits.
Mesoscopic theory is applied to show the nanoparticles migration through a porous 3D cavity. Various amounts of Lorentz forces, buoyancy and Darcy number on working fluid behavior are considered and depicted. Al2O3-H2O is selected including Brownian motion effect. Outputs are illustrated in views of streamlines, isokinetic and isotherms contours. Outputs display that the enhancing magnetic forces lead to rise in conduction mode. Nu_ave augments with the decrease in Lorentz forces while it improves for stronger Lorentz forces.
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.
The present study develops the new fin geometry with the objective of boosting the effectiveness of solar energy storage applications. A triplex-tube structure is utilized, where both the inner and outer fluid channels receive heated fluid from a concentrated solar setup. The phase change material (PCM), paraffin RT60, is augmented with a hybrid nanoparticle mixture of silicon carbide (SiC) and carbon nanotubes (CNTs) at a 0.02 vol fraction to improve its thermal conductivity. The numerical simulation is performed employing the FLUENT software and validated against well-established benchmarks in melting studies. To evaluate the influence of hybrid nanoparticle dispersion and fin configurations on thermal performance, four main cases are analyzed. Two novel tree-shaped fin designs—discrete and continuous—are introduced to boost heat transfer and accelerate phase change. The outputs showed that integrating hybrid nanoparticles into paraffin decreases melting and freezing durations by approximately 8.18 % and 13.85 %, respectively. However, the continuous tree-shaped fin configuration proves to be the most efficient, significantly improving energy storage performance. Relative to the base case, which excludes fins and nanoparticle enhancements, this setup reduces melting time by 52.59 % and solidification time by 80.91 %, demonstrating a remarkable enhancement in heat transfer efficiency.
In this manuscript, we present nanofluid thermal management inside a porous media including magnetic force and radiation heat sources. The systems of PDEs were changed into the non-dimensional form by means of the suitable transform. To gain the outputs, control volume finite element method (CVFEM) was utilized. Radiative source term was involved in final PDEs. Isotherms and streamlines are plotted to demonstrate the variation of Hartmann number, radiation factor, buoyancy and nanoparticles' shape on nanofluid behavior. Outputs demonstrate that convective mode becomes stronger with augment of shape factor. By involving source terms of magnetic field, conduction becomes more effective. Average Nusselt number grows as enhancing the shape effect parameters “m”, Radiation effect and Raleigh number. As increasing Radiation and Raleigh parameters average temperature deceases gradually. The comparative study is also presented, which shows the reliability and efficiency of the CVFEM. Graphical study also shows strengthen of suggested technique.
Control volume based finite element method (CVFEM) is applied to investigate flow and heat transfer of CuO–water nanofluid in presence of magnetic field. The enclosure has a sinusoidal wall under constant heat flux. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity is considered. The numerical investigations are conducted at a fixed Prandtl number equal to 6.2. Various values of non-dimensional governing parameters such as volume fraction of nanoparticles (ϕ), Rayleigh number (Ra), dimensionless amplitude of the sinusoidal wall (a) and Hartmann number (Ha) are examined. Also a correlation of Nusselt number corresponding to active parameters is presented. The results show that Nusselt number is an increasing function of nanoparticles volume fraction, dimensionless amplitude of the sinusoidal wall and Rayleigh number while it is a decreasing function of Hartmann number.
No abstract is provided for this article.
This article explores the effect of thermal radiation on Al2O3–water nanofluid flow and heat transfer in an enclosure with a constant flux heating element. KKL (Koo–Kleinstreuer–Li) correlation is used for simulating effective thermal conductivity and viscosity of nanofluid. The governing equations are solved via control volume based finite element method. The effects of Rayleigh number, Hartman number, viscous dissipation parameter, radiation parameter and volume fraction of nanoparticle on the flow and heat transfer characteristics have been examined. Results show that enhancement in heat transfer has direct relationship with Hartman number, viscous dissipation parameter and radiation parameter but it has reverse relationship for Rayleigh number. It is also observed that Nusselt number is an increasing function of Rayleigh number, volume fraction of nanoparticle and radiation parameter while it is a decreasing function of viscous dissipation parameter and Hartman number.
Current article devoted to simulation of passive techniques impact on reduction of solidification time within a tank with two cold surfaces which are connected to cold fluid flows. Design of current unit is based on NEPCM and wavy shape of inner wall. Addition of powders can enhance the discharging rate and it is more sensible for greater shape factor. In view of energy absorbed, time of solidification is very important. Complete discharging occurs when all liquid convert to solid. Outputs demonstrated that the times required for full solidification augments with reduce of shape factor and similar behavior was observed for amplitude of wavy cylinder. Faster solidification can take place as a consequence of greater shape factor.
Experimental analysis on pressure loss and heat transfer improvement in an air to water double pipe heat exchanger is presented. Typical circular-ring (TCR) and perforated circular-ring (PCR) turbulators, assumed as turbulators. Water and air move through inner and outer pipes, respectively. Experimental analysis is conducted for various values of open area ratio (0, 0.0208, 0.0416 and 0.0833), Reynolds number (6000, 8000, 10,000 and 12,000) and pitch ratio (1.83, 2.92 and 5.83). According to experimental data, correlations for Nusselt number, friction factor and thermal performance are presented as functions of Reynolds number, pitch ratio and open area ratio. Sensitivity analysis is used to find the effect of each active parameter. Results indicated that using PCRs leads to obtain lower heat transfer enhancement than the CRs. Thermal performance increases with increase of open area ratio but it reduces with rise of pitch ratio and Reynolds number. The most effective parameter for thermal performance is open area ratio.
In this paper, experimental analysis is examined to estimate hydrothermal behavior of refrigerant-based nanofluid (nano-refrigerant) during condensation inside a horizontal tube. In order to produce nano-refrigerant, R600a and CuO are selected as base fluid and nanoparticle, respectively. Roles of mass flux, vapor quality, concentration of nanoparticles are investigated. Results indicate that the presence of nanoparticles generally increased the frictional pressure drop. The Brownian motion as well as the deposition of a molecular layer of nanoparticles on the inner tube surface intensifies the conduction and micro-convection in the fluid.
Electric field effect on nanofluid forced convective heat transfer in an enclosure with sinusoidal wall is presented. Control Volume based Finite Element Method (CVFEM) is utilized to simulate this problem. Fe3O4–ethylene glycol nanofluid is used as working fluid. Numerical investigations are conducted for several values of Reynolds number, nanoparticle volume fraction and supplied voltage. Results show that supplied voltage can change the flow shape. Coulomb force causes isotherms to be denser near the moving wall. Heat transfer rises with augmentation of supplied voltage and Reynolds number. The effect of electric field on heat transfer is more pronounced at low Reynolds number.
Heat transfer of a nanofluid flow which is squeezed between parallel plates is investigated analytically using homotopy perturbation method (HPM). Copper as nanoparticle with water as its base fluid has been considered. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. This investigation is compared with other numerical methods and they were found to be in excellent agreement. The effects of the squeeze number, the nanofluid volume fraction and Eckert number and δ on Nusselt number are investigated. The results show that Nusselt number has direct relationship with nanoparticle volume fraction, δ, the squeeze number and Eckert number when two plates are separated but it has reverse relationship with the squeeze number when two plates are squeezed.
The use of additives in the base fluid like water or ethylene glycol is one of the techniques applied to augment the heat transfer. Newly an innovative nanometer sized particles have been dispersed in the base fluid in heat transfer fluids. The fluids containing the solid nanometer size particle dispersion are called ‘nanofluids’. Two main categories were discussed in detail as the single-phase modeling which the combination of nanoparticle and base fluid is considered as a single-phase mixture with steady properties and the two-phase modeling in which the nanoparticle properties and behaviors are considered separately from the base fluid properties and behaviors. Both single phase and two phase models have been presented in this paper. This paper intends to provide a brief review of researches on nanofluid flow and heat transfer via semi analytical and numerical methods. It was also found that Nusselt number is an increasing function of nanoparticle volume fraction, Rayleigh number and Reynolds number, while it is a decreasing function of Hartmann number.
The current investigation numerically scrutinizes exergy loss and heat transfer of mixture of Aluminum oxide and H2O through a solar collector. Finite volume method has been employed with considering realizable k − ε . Such turbulence model has been selected because of best agreement with previous experimental outputs. To assure the accuracy of code, comparisons with numerical and experimental outputs have been provided for different Reynolds number (Re), number of revolution (N) and diameter ratio (D*). Dispersing Al2O3 is apparently able to offer a more promotion on second law's performance. More turbulence mixing occurs when employing a turbolentor with extra revolution. As diameter ratio augments, exergy loss drops due to reduction of surface temperature. Increasing inlet velocity brings about a significant reduction in surface temperature which results in less exergy loss.
Influence of perforated and typical helical fin on hydrothermal treatment in a water to air heat exchanger is presented. Air and water move through outer and inner pipes, respectively. Effects of pitch ratio (λ), Reynolds number (Re a ) and open area ratio (PR) are examined. Empirical formulae for thermal performance (η), Darcy factor (f) and Nusselt number (Nu) are obtained. NSGA II and ANSYS FLUENT14 are chosen for optimization and numerical simulation. Results indicate that higher open area ratio offers greater thermal performance than the lower one. Temperature gradient attenuates with enhance of open area ratio.
