Augmentation of heat transfer via nanofluids in duct flows using Fourier-type conditions: Theoretical and numerical study

Motivated by developments in thermal duct processing, an investigation is presented to study the behavior of viscous nanoparticle suspensions flowing in a vertical duct subject to Fourier-type conditions. The left wall temperature is kept lower than that of the right wall. Brownian motion and thermophoresis which are invoked via the presence of nanoparticles are incorporated in the study. Numerical solutions with an efficient Runge–Kutta shooting method are also presented at all values of the control parameters. The impact of thermal Grashof number [Formula: see text], Eckert number [Formula: see text], thermophoresis [Formula: see text], and Brownian motion parameters [Formula: see text] on the velocity, temperature, and nanoparticle concentration distributions for identical [Formula: see text] and differing Biot numbers [Formula: see text] (at the duct walls) are computed and visualized graphically. With vanishing thermophoresis and Brownian motion parameters, the solutions match exactly with the earlier Newtonian viscous flow computations. Symmetric and asymmetric wall heat conditions are also acknowledged. Intensifying the thermal Grashof number, Eckert number, thermophoresis parameter, and Brownian parameter serve to amplify magnitudes of the velocity and temperature, whereas the nanoparticle concentration field is suppressed. The skin friction and Sherwood number are also computed with various combinations of the flow control parameters. Nusselt number values at the hot duct wall are enhanced with an increase in thermal buoyancy parameter, Eckert number, Brownian motion parameter, and thermophoresis parameter for equal Biot numbers. The opposite trend is computed for different Biot numbers. For any given values of Biot numbers, the mean velocity and bulk temperature are boosted with increase in thermal buoyancy parameter, Eckert number, Brownian motion parameter, and thermophoresis parameter. Hence, it may be inferred that the transport characteristics computed using Fourier-type boundary conditions are substantially different from those based on isothermal boundary conditions in nanofluid duct flows.

INFRARED DEHYDRATION OF BLANCHED QUINCE SLICES: STUDY ON PROCESS AND MASS TRANSFER CHARACTERISTICS

In the present work, moisture removal characteristics of quince slices in a convective tray dryer were studied. The blanched slices (with thicknesses of 3, 5 and 7 mm) were dried at drying temperatures of 50, 60 and 70 °C and air flow rates of 1, 1.5 and 2 m/s. The analytical model proposed by Dincer and Dost was used to determine the mass transfer parameters. The obtained Biot numbers (0.108‒0.293) revealed that both the internal and external resistance control the moisture diffusion within the samples. The moisture diffusivity and convective mass transfer coefficient were found to be in the ranges of 1.578×10-7‒7.331×10-7 m2/s and 2.040×10-5‒3.507×10-5 m/s, respectively. The activation energies for moisture diffusion and surface mass evaporation were determined to be in the ranges of 17.607 to 48.019 kJ/mol and 5.270 to 27.430 kJ/mol, respectively.

Bioconvection in Magneto Hydrodynamics Casson Nanoliquid (Fe3O4-Sodium Alginate) With Gyrotactic Microorganisms Over an Exponential Stretching Sheet

The present investigation focuses on the influence of motile gyrotactic microorganisms and thermal heat flux on three-dimensional convective flow of a Casson nanoliquid over an elongated surface. The flow equations are modelled by using Tiwari-Das nanofluid model. Sodium alginate (SA) is considered as the base fluid together with Ferromagnetic oxide (Fe3O4) nanoparticles. The governing flow equations are changed into a system of ODEs with the aid of similarity variables and are then addressed computationally. Influence of various pertinent parameters on different physical quantities is examined graphically. The outcomes of present investigation is validated through comparison study and is found to be in good arrangement. It is noticed that the coefficient of heat transfer rises with growing radiation and Biot numbers. Also the mass transfer coefficient surges for higher values of Schmidt number and generative chemical reaction parameter.

Numerical heat transfer in annular fins of curved profile formed with the intersection of two equal circles

Purpose The purpose of this paper is to investigate the heat transfer attributes of annular fins with quarter circle profile in terms of the Biot number Bi and the radius ratio rr. The latter corresponds to the internal radius of the tube divided by the length of the fin in question. Design/methodology/approach To this end, the governing two-dimensional (2-D) heat conduction equation in cylindrical coordinates is numerically solved via finite element analysis for different Bi (i.e., 0.1, 1 and 5) and rr (i.e., 0.5, 1 and 2). Findings The obtained results for the mid-plane and surface temperatures show that these profiles, which exhibit nearly rr-independent responses, only present one-dimensional (1-D) radially linear distributions for the case Bi = 1. For Bi = 0.1, the temperature profiles also possess a 1-D character but with a clearly defined concave pattern. Finally, for Bi = 5, a 2-D temperature field in a wide zone from the fin base is achieved with a convex pattern for the mid-plane and surface temperatures. Originality/value Exhaustive assessment of the heat transfer in annular fins with quarter circle profile in terms of different Biot numbers and radius ratios

Unsteady squeezing flow of a magnetized nano-lubricant between parallel disks with Robin boundary conditions

The aim of the present work is to examine the impact of magnetized nanoparticles (NPs) in enhancement of heat transport in a tribological system subjected to convective type heating (Robin) boundary conditions. The regime examined comprises the squeezing transition of a magnetic (smart) Newtonian nano-lubricant between two analogous disks under an axial magnetism. The lower disk is permeable whereas the upper disk is solid. The mechanisms of haphazard motion of NPs and thermophoresis are simulated. The non-dimensional problem is solved numerically using a finite difference method in the MATLAB bvp4c solver based on Lobotto quadrature, to scrutinize the significance of thermophoresis parameter, squeezing number, Hartmann number, Prandtl number, and Brownian motion parameter on velocity, temperature, nanoparticle concentration, Nusselt number, factor of friction, and Sherwood number distributions. The obtained results for the friction factor are validated against previously published results. It is found that friction factor at the disk increases with intensity in applied magnetic field. The haphazard (Brownian) motion of nanoparticles causes an enhancement in thermal field. Suction and injection are found to induce different effects on transport characteristics depending on the specification of equal or unequal Biot numbers at the disks. The main quantitative outcome is that, unequal Biot numbers produce significant cooling of the regime for both cases of disk suction or injection, indicating that Robin boundary conditions yield substantial deviation from conventional thermal boundary conditions. Higher thermophoretic parameter also elevates temperatures in the regime. The nanoparticles concentration at the disk is boosted with higher values of Brownian motion parameter. The response of temperature is similar in both suction and injection cases; however, this tendency is quite opposite for nanoparticle concentrations. In the core zone, the resistive magnetic body force dominates and this manifests in a significant reduction in velocity, that is damping. The heat build-up in squeeze films (which can lead to corrosion and degradation of surfaces) can be successfully removed with magnetic nanoparticles leading to prolonged serviceability of lubrication systems and the need for less maintenance.

Optimal Shape of Non-Linear Partially Wet Annular Fins for Maximum Efficiency

Heat exchangers with annular finned-tube type and partially wetted condition are utilized widely in engineering systems, such as air-conditioning systems and refrigeration systems. In addition, the physical properties of fin materials should be considered as functions of temperature in reality and thus become a non-linear problem. Based on the above two conditions, an optimal partially wet annular fin design problem, with temperature-dependent thermal properties of the fin, to yield optimal fin efficiency was investigated in the present work, which has not been examined previously and it is the novelty of this study. An iterative regularization algorithm using the conjugate gradient method (CGM) is considered as the optimization tool based on the desired fin efficiency under a fixed fin volume constraint. The partially wet annular fin condition can result if the relative humidity of surrounding air is between 80 and 90%. Finally, the optimal fin shape, with the highest computed efficiency among examined fins under identical operational conditions, can be obtained. It is found that when the Biot numbers for ambient air (Bia) and relative humidity (φ) increased, the optimum computed fin efficiency and interfacial radius between wet and dry fin domains (rwd) will be increased, and the estimated optimum fin shape also changed. However, the shape of optimal fin remained approximately unchanged when the Biot numbers for the inner tube (Bii), the thermal conductivities of the tube (kw) and fin (kf) varied. It reveals that Bii, kw and kf have an insignificant influence on the optimal shape of the annular fin in a partially wet condition.

An Analytic Solution for Electrical Magneto-Hydrodynamics Darcy–Forchheimer Three Dimensional Non-Newtonian Nanofluid Flow with Convective Boundary Conditions

In this article, the treatment of three-dimensional non-Newtonian Williamson fluid has been carried out under examination. Using the standard transformation, the governing equations are converted into universal similarity equations which have been solved by the optimal homotopy asymptotic method. We observed that the method is effective, reliable, consistent and efficient in solving strongly nonlinear differential equations. The influence of embedded parameters on the fluid flow has discovered graphically and using table. The velocity profile in the x-direction is increased with magnetic and electric field parameters and decreased with the increased stretching parameter, coefficient of inertia, velocity slip parameter L1 and porosity parameters. The velocity profile in the y-direction is increased with magnetic and electric field parameters, the distended stretching parameter, while reduced with the velocity slip parameter L2, coefficient of inertia, and porosity parameters. The temperature profile is increased with the radiation, thermophoresis and Brownian motion parameters, and Biot number. The profile of concentration is rising with the enlarged Biot numbers and thermophoresis parameter, while reduced with the Brownian motion parameter.

Modeling and theoretical investigation of curved parabolized surface of second-order velocity slip flow: Combined analysis of entropy generation and activation energy

Here our purpose is to explore the entropy generation in nanofluid MHD flow by curved stretching sheet; second-order slip is considered. Additional effects of viscous dissipation, Joule heating, and activation energy are taken. Temperature and concentration boundary conditions are considered convectively. For convergence of series solution NDSolve MATHEMATICA is used. Velocity, Bejan number, concentration, temperature, and entropy generation graphs are sketched for important parameters. For greater estimations of first- and second-order velocity slip parameters fluid velocity reduces. The thermal and solutal Biot numbers enhance the temperature and concentration, respectively. The concentration also has direct relation with activation energy. Entropy generation reduces for chemical reaction parameter and first- and second-order slip parameters.

Stability Analysis of the Magnetized Casson Nanofluid Propagating through an Exponentially Shrinking/Stretching Plate: Dual Solutions

In this research, we intend to develop a dynamical system for the magnetohydrodynamic (MHD) flow of an electrically conducting Casson nanofluid on exponentially shrinking and stretching surfaces, in the presence of a velocity and concertation slip effect, with convective boundary conditions. There are three main objectives of this article, specifically, to discuss the heat characteristics of flow, to find multiple solutions on both surfaces, and to do stability analyses. The main equations of flow are governed by the Brownian motion, the Prandtl number, and the thermophoresis parameters, the Schmid and Biot numbers. The shooting method and three-stage Lobatto IIIa formula have been employed to solve the equations. The ranges of the dual solutions are f w c 1 ≤ f w and λ c ≤ λ , while the no solution ranges are f w c 1 > f w and λ c > λ . The results reveal that the temperature of the fluid increases with the extended values of the thermophoresis parameter, the Brownian motion parameter, and the Hartmann and Biot numbers, for both solutions. The presence of dual solutions depends on the suction parameter. In order to indicate that the first solution is physically relevant and stable, a stability analysis has been performed.

Effect of Cooling Methods on the Strength of Silico-ferrite of Calcium and Aluminum of Iron Ore Sinter during the Cooling Process

In the iron making process, a high mechanical strength is favorable for iron ore sinters in the blast furnace, and the bonding phase is regarded as one of the key components that determines the quality of the iron ore sinter, in which the silico-ferrite of calcium and aluminum (SFCA) is one of the typical phases. In this study, synthesized samples with different SFCA mass fractions were prepared to study the effect of different cooling methods on the strengths of the SFCA samples. The results showed that the strength of a sample could be improved by increasing the SFCA content during a temperature change. Further, the test results for the compressive strength suggested that the SFCA had a positive effect on the strength of the iron ore sinter during cooling, with slow cooling being significantly effective at preventing the generation of thermal stress. Moreover, the Biot number was introduced to normalize all of the cooling methods. The results showed that higher mechanical strengths for iron ore sinters will be obtained with higher SFCA content and lower Biot numbers, which will guide the evaluation of mechanical strength of iron ore sinter after the cooling process in industry.