International Journal of Thermofluids最新文献

Thermosolutal attributes of Maxwell fluid over a riga wedge subjected to Falkner-Skan flow is described in current work. The effectiveness of the temperature-dependent viscosity and conductivity, along with the consideration of the radiative and activation energies, are included. Problem structuring is conceded into ODE's after utilizing similar variables on the PDE's. An efficient technique bvp4c in MATLAB is implemented to numerically tackle the nonlinear equations. Graphical outcomes are expressed for various involved factors by accounting three different wedge situations are illustrated i.e. λ = 0 (static), λ < 0 (shrinking) and λ > 0 (stretching). Wall drag, heat and mass gradients are also enumerated in comparative sense. Wide range of parameters are defined for instance, 0.3 ≤ A ≤ 0.7,  0.2 ≤ β ≤ 0.6,  0.5 ≤ M ≤ 1.5,  0.2 ≤ Bi ≤ 0.7,  0.5 ≤ m ≤ 1.3,  2.0 ≤ Pr ≤ 3.0,  0.3 ≤ Q ≤ 0.7,  and 0.2 ≤ Rd ≤ 0.6. The present study concludes that the velocity profile becomes progressive in the presence of larger values of the Deborah number and the unsteadiness parameter along the static, stretching, and shrinking wedges. The temperature profile shows the same elevating behavior corresponding to the radiation parameter and Biot number. The wall drag force is found to be reduced, and contrary aspects were noticed in the heat flux coefficient when the wedge is stretched compared to the other two cases.

This study investigates the magnetohydrodynamic (MHD) flow of Carreau nanofluid through a porous medium with motile microorganisms, focusing on various geometries under shear-thinning and shear-thickening conditions. The aim is to elucidate how factors such as activation energy, Schmidt number, Peclet number, bioconvection, Brownian motion, thermophoresis, and heat generation influence flow dynamics. Using similarity transformations, we nondimensionalize the governing equations and solve them numerically with the Runge–Kutta method and a shooting technique in MATLAB. Our findings indicate that variations in Carreau, magnetic, and suction parameters notably impact velocity, temperature, concentration, diffusion, wall friction, and heat transfer, generally resulting in reduced values. Specifically, the flat plate geometry exhibits lower skin friction, heat transfer, and mass transfer rates, as well as decreased gyrotactic microorganism effects. Increased activation energy enhances concentration fields, signaling slower chemical reactions, while higher Peclet numbers and bioconvection inversely affect flow properties. Additionally, reduced Schmidt numbers lead to lower microorganism concentrations. These results provide valuable insights into the complex interactions between fluid dynamics and microorganism behavior, with implications for optimizing processes in biotechnology and environmental management.

Due to the necessity of performing thermal operations, heat exchangers are widely employed in many different areas. The heat transfer and fluid flow within a spiral double-pipe heat exchanger fitted with a novel turbulator were numerically assessed in this work. The presented novel turbulator is a curved tube with holes incorporated into its thickness and spiral ribs on its inner wall. The turbulator wall's curved rib design produces secondary flows at the turbulator output when fluid flows through the tube and the perforations. A commercial CFD tool, based on the finite volume technique, was used to conduct the numerical simulations. The fluid flow regime is turbulence (Re = 8,000 – 14,000). Two sections make up this work. The first portion looked at how the hydrothermal behavior of the fluid flow inside the proposed turbulator was affected by the angle at which the curved ribs rotated. For this angle, three values were considered: θ = 30, 90, and 150°, and the outcomes were contrasted with those of a plain spiral double-tube heat exchanger (turbulator not included). Then, the number of embedded holes in the turbulator's thickness changes in the second part, and three values of N = 12, 16, and 20 were considered. According to the first part's findings, the model exhibiting θ = 90° had a greater thermal performance factor at Re = 10,000. This model has a more noteworthy thermal performance factor than the models with θ = 150 and θ = 30° by approximately 15.62 % and 22.65 %, respectively (at Re = 10,000). Furthermore, the second section's numerical findings showed that the model with N = 20 had more extraordinary thermal performance at Re = 10,000. Model N = 20 has a thermal performance factor of about 16.93 % and 17.55 % greater than models N = 16 and N = 12. Within the proposed heat exchanger, the recommended turbulator produced a sizable rotating flow, and including embedded holes significantly reduced the pressure drop this kind of turbulator causes.

In this paper, the thermal conductivity (k_nf) of the Al₂O₃/Ethylene Glycol -Water nanofluid is measured. MATLAB software is used to fit a nonlinear function, and the analysis of variance (ANOVA) is implemented to determine the effect of temperature and volume fraction of nanoparticles (φ) on extracting the residuals and k_nf. In the experimental part, various combinations of temperatures (from 30 to 60 °C) and volume fractions (fromφ = 0.15 up to 1.3%) are examined, and then the obtained data are analyzed using MINITAB software. The results show that the k_nf is highly dependent on φ and less dependent on temperature. By changing the φ from 0.15 to 1.3%, the thermal conductivity increases around 40%. In contrast, increasing the temperature from 30 to 60 °C will increase the k_nf by almost 10%. Also, the results show that the thermal conductivity slope is lower at φ < 0.75%, and this rate increases drastically for higher volume fractions. The obtained results, especially the fitting function, are useful for designing and optimizing systems using nanofluids as a working fluid in heat exchangers or energy systems.

This study examines the heat transfer enhancement and pressure drop of Al₂O₃ nanofluid in deep dimpled tubes in both longitudinal and circumferential directions. It explores mechanisms that improve the thermal performance of this novel tube geometry. Experiments were conducted using plain and deep dimpled tubes under laminar flow with Reynolds numbers from 500 to 2250, a constant heat flux of 10,000 W/m², and nanofluid concentrations from 0.1 wt% to 1 wt%. The findings indicate that local velocity enhancement, vortex generation, and flow rotation and mixing are the three main mechanisms that improve the thermal performance of deep dimpled tubes. The results demonstrate that a deep dimpled tube with 1 wt% nanofluid can increase the convective heat transfer coefficient by up to 3.42 times compared to a smooth tube at Re = 2250. At this Reynolds number, the Nusselt number reaches a maximum of 41.80, and the friction factor ratio increases by only 1.82. Additionally, circumferential analysis reveals how dimple-induced vortices enhance heat transfer. The results also indicate that the tube geometry modification changes the flow regime zones, allowing turbulent flow at lower Reynolds numbers near Re = 2000, as identified by Nusselt number and friction factor plots. The deep dimpled tube has a low improvement penalty, with the highest friction factor of 0.38 at Re = 500 and high thermal enhancement, resulting in a performance evaluation criterion (PEC) of up to 2.80 in the studied region. However, the deep dimpled tube is unsuitable for Reynolds numbers below 1000. For higher velocities, replacing simple tubes with deep dimpled tubes in traditional heat exchangers is highly recommended.

In the current work, flow of 2-D MHD Walters'B viscoelastic fluid is discussed in the existence of elastic deformation, Cattaneo–Christov Heat Flux Model (CCHFM), heat source, Newtonian heating, viscous dissipation and porous medium. Dimensionless equations that are in charge of the problem's analysis are produced by using the suitable similarity transformation, and Optimal Auxiliary Functions Method (OAFM) is employed to solve them. In the ongoing investigation, the main results are decreasing behavior of temperature profile for the thermal relaxation parameter and elastic deformation parameter, while the reverse effect is noticed while increasing the Weissenberg number and porosity parameter. Our findings reveal significant insights into the fluid dynamics and heat transfer characteristics. Integrating the Cattaneo–Christov heat flux model and elastic deformation analysis in Walters'B viscoelastic fluid flow having its importance in polymer processing, aerospace engineering and waste treatment systems.

Present study explores mixed convection characteristics in a long horizontal channel subjected to multiple periodically distributed flow modulators. The flow modulators are represented by oscillating blades placed along a centerline of the channel whose lower and upper walls are kept at constant high and low temperatures respectively. In replicating the blade oscillation, moving mesh approach has been adopted within Arbitrary Lagrangian–Eulerian (ALE) framework for a representative periodical unit. The corresponding non-dimensional governing mass, momentum and energy conservation equations have been solved through Galerkin finite element solver for a wide variations of modulator's dynamic condition (oscillating frequency and maximum angular displacement) for different fluids represented by Prandtl number. Heat transfer performance of the system has been demonstrated in terms of spatially-averaged transient as well as time-averaged Nusselt number while qualitative analysis of fluid flow and thermal field has been presented as streamline and isotherm plots. Present study indicates that the time averaged Nusselt number undergoes significant variation with blade oscillating frequency and maximum angular displacement depending on both the Prandtl number and Reynolds Number. Power spectrum analysis obtained through Fast Fourier Transformation (FFT) of the imposed blade frequency and induced thermal frequency reveals different correlation depending on the blade frequency. Blade friction power requirement has been found to increase at higher blade frequency as well as maximum angular displacement. However, contrary to power consumption, increase in frequency does not result in a significant rise in heat transfer. Consequently, specific heat transfer decreases at higher blade oscillating frequency and maximum angular displacement.

This description focuses on how the magnetic field affects mass and heat transfer in a hybrid nanofluid (Hnf) between two parallel, rotating plates. By dispersing aluminum oxide (Al₂O₃) and molybdenum disulfide (MoS₂) nanoparticles (NPs) in ethylene glycol (EG), a hybrid nanofluid (Hnf) is created. This research aims to analyze the heat and mass transfer characteristics in the flow of a hybrid nanofluid (MoS₂-Al₂O₃/EG) between two rotating parallel plates under the influence of a magnetic field. Furthermore, the statistical technique of response surface methodology (RSM) has been employed to optimize the parameters of velocity, temperature, and concentration of the nanofluid within the flow region bounded by the rotating plates. Dimensionless differential equations have been calculated and checked using the Homotopy perturbation method. This study introduces a novel approach by utilizing the RSM method to identify optimal points for velocity and temperature parameters of nanofluids between two stretching plates for the first time. Additionally, the article innovatively applies the exact HPM method to validate dimensionless linear and non-linear coupling equations. As the Reynolds number and the suction/injection coefficient of nanofluids flowing between two plates under tension increase, the results indicate a decrease in the velocity field. This decrease in velocity field can be attributed to the reduction in fluid diffusion as viscous forces diminish with varying Reynolds numbers. The ideal temperature distribution for nanofluids flowing between two parallel plates occurs when they are uniformly dispersed at the midpoint between them. As the distance from the initial point of nanofluid entry to the end of the plates increases, along with the vertical distance from the bottom plate, the temperature gradient diminishes, reducing the thickness of the thermal boundary layer. The velocity gradient and the rate of heat flux transfer between the nanofluid and plate rise by 34 % when the volume percentage is raised from 1 % to 5 %.

The need for desalination is expected to evolve, and interests in novel techniques to enhance thermal desalination are developing. Research studies on ultrasonic atomization for desalination application has been observed in the last few years. Hence, this study aims to examine humidification process enhancement using ultrasonic atomization and interaction of atomized droplets with hot air in the humidifier. In the Humidification and Dehumidification (HDH) desalination system examined, the humidifier is equipped with a single ultrasonic atomizer unit which operates continuously with preheated hot air entering the humidifier chamber. The system is investigated for different air flowrates (40 – 100 LPM) and hot air temperatures (40, 50, and 60 °C). The average relative humidity at the humidifier outlet was maximum reaching 94 % for the highest flowrate. The results indicate that increasing hot air temperatures have significant improvement in droplet evaporation which causes higher relative humidity at the outlet, and increasing hot air flowrates have significant impact on the faster response of the humidification process to reach equilibrium.