Presence Of Heat Research Articles

Non-Linear Convection in Chemically Reacting Fluid with an Induced Magnetic Field across a Vertical Porous Plate in the Presence of Heat Source/Sink

An investigation is carried out to observe the impacts of non-linear convection and induced magnetic field in the flow of viscous fluid over a porous plate under the influence of chemical reaction and heat source/sink. The plate is subjected to a regular free stream velocity as well as a suction velocity. The subjected non-linear problem is non-dimensionalized and analytic solutions are presented via perturbation method. The graphs are plotted to analyze the effect of relevant parameters on velocity, induced magnetic field, heat and mass transfer fields as well as friction factor, current density, Nusselt and Sherwood numbers. It is established that nonlinear convection aspect is destructive for thermal field and its layer thickness. The magnetic field effect enhances the thermal field while it reduces the velocity field. Also, the nonlinear effect subsides heat transfer rate significantly.

Flow and heat transfer of nanofluid over an exponentially shrinking porous sheet with heat and mass fluxes

Steady boundary layer flow of nanofluid past an exponentially porous shrinking sheet in presence of heat and mass fluxes is presented. In this model the combined effects of Brownian motion and thermophoresis on heat transfer and nanoparticle volume fraction are considered. Similarity transformations are used to obtain the self-similar equations which are then solved numerically using shooting technique along with fourth order Runge-Kutta method. Similarity solution depends on the suction parameter. This investigation reveals that the variable heat flux and mass flux have major significant effects on temperature field and the nanoparticle volume fraction. The wall mass transfer through the porous sheet causes an increase of fluid velocity for the first branch of solution. Temperature as well as nanoparticle volume fraction decreases for both branches of solutions. For the Brownian motion, the temperature increases but the nanoparticle volume fraction decreases. Heat transfer rate becomes lower with the increase of Lewis number. Due to increase in thermophoresis parameter, both the temperature and nanoparticle volume fraction increase.

A comparative study of individual influences of suspended multiwalled carbon nanotubes and alumina nanoparticles on Rayleigh-Bénard convection in water

The generalized Lorenz model for studying the Rayleigh-Bénard convection in water-multiwalled carbon nanotubes and water-alumina in the presence of heat source/sink is derived using a tri-modal, Fourier series representation under the assumption of the Boussinesq approximation and small-scale convective motion. On the premise that the multiwalled carbon nanotubes/alumina nanoparticles undergo all motions which water particles undergo the single-phase description of the Khanafer-Vafai-Lightstone model can be adopted. The thermophysical properties of the two nanoliquids are calculated using the phenomenological laws and traditional mixture theory. The transition of the dynamical Lorenz system from stability to chaos followed by periodic motion in a window of periodicity and then a sequence of such motions are explained in detail by calculating the maximum Lyapunov exponent. Specifically, the individual effect of multiwalled carbon nanotubes and alumina nanoparticles on the stability of the dynamical system is investigated from a new perspective of time series solution and attractors of the Lorenz model. We then study the individual influence of multiwalled carbon nanotubes and alumina nanoparticles on the onset of convection and heat transport. The findings of a feasibility study indicate that less expensive spherical alumina nanoparticles are preferable in heat transfer applications over the more expensive multiwalled carbon nanotubes, in spite of the latter having a larger surface area and higher thermal conductivity. It is found that exactly the same amount of heat transfer obtained by using multiwalled carbon nanotubes can be achieved by replacing them with a slightly higher volume fraction of the much cheaper alumina nanoparticles.

A Numerical Investigation of 3D MHD Rotating Flow with Binary Chemical Reaction, Activation Energy and Non-Fourier Heat Flux**Supported by the Korea Ministry of Trade, Industry and Energy, “Energy Technology Development Work in 2017”, Project No. 20172010105570

In this investigation we analyze the rotating three-dimensional magnetohydrodynamic flow of Maxwell fluid in attendance of binary chemical reaction with activation energy. Furthermore, effects of non-Fourier heat flux are taken into account. Formulation is done in the presence of heat and mass convective boundary conditions. Self-similar forms from boundary layer equations are obtained using apposite transformations. Numerical solution is obtained via built-in bvp-4c function in MATLAB for the system of differential equations. Effects of ensuing parameters on flow distributions are portrayed graphically. It is witnessed that increasing values of rotational parameter lowers the velocity profile and both Biot numbers have escalating effect on temperature and concentration distributions. A comparative study to a previously done investigation is also included to corroborate our results.

Magnetohydrodynamics Stagnation-Point Flow of Sisko Liquid With Melting Heat Transfer and Heat Generation/Absorption

This research concentrates on melting heat transfer in magnetohydrodynamics (MHD) flow of Sisko fluid bounded by a sheet with nonlinear stretching velocity. Modeling and analysis have been carried out in the presence of heat generation/absorption and magnetic field. Transformation procedure is implemented in obtaining nonlinear differential system. Convergence series solutions are developed. The solution for different influential parameters is analyzed. Skin friction coefficient and heat transfer rate are analyzed. It is observed that the qualitative results of magnetic field and melting heat transfer on velocity are similar.

Comparison of different in situ measurements techniques of intelligibility in an open-plan office

Acoustic comfort in open-plan offices is a relatively recent research topic and some practices have not yet been consolidated. The goal in these spaces is to achieve good speech privacy at every workstation, reaching a high value of spatial decay of the sound pressure level. In case of refurbishment, a proper measurement of intelligibility criteria is needed, for example, in order to properly calibrate a numerical model or to plan acoustic treatments. This work compares different measurement techniques to evaluate the spatial distribution of intelligibility criteria. In situ measurements were done in an open-plan office used as a case study. Both omnidirectional and directional sound sources with different sound power levels were used, according, respectively, to ISO 3382-3:2012 and ITU-T P.51:1996. Furthermore, compensation algorithms were used in impulse response measurements in presence of Heating, Ventilation and Air Conditioning noise. The study shows, in a preliminary way, how different techniques and equipment can influence intelligibility criteria used in the open-plan office characterization. Results show that the indirect method of measuring Speech Transmission Index could not be used when the background level is high as the case study while the direct method returns good results.

MHD Flow of Sisko Fluid Over a Bidirectional Radiating Stretching Surface Embedded in a Nanofluid Saturated Porous Media in the Presence of Heat Generation/Absorption and Chemical Reaction

MHD Flow of Sisko Fluid Over a Bidirectional Radiating Stretching Surface Embedded in a Nanofluid Saturated Porous Media in the Presence of Heat Generation/Absorption and Chemical Reaction

Degradation of hydraulic fracturing additive 2-butoxyethanol using heat activated persulfate in the presence of shale rock

Changes in fluid composition during hydraulic fracturing (HF) for natural gas production can impact well productivity and the water quality of the fluids returning to the surface during productivity. Shale formation conditions can influence the extent of fluid transformation. Oxidizers, such as sodium persulfate, likely play a strong role in fluid transformation. This study investigates the oxidation of 2-butoxyethanol (2-BE), a surfactant used in HF, by sodium persulfate in the presence of heat, pH changes, Fe(II), and shale rock. Increasing temperature and Fe(II) concentrations sped up 2-BE oxidation, while pH played little to no role in 2-BE degradation. The presence of shale rock impeded 2-BE oxidation with increasing shale concentrations causing decreasing pseudo-first-order reaction rate constant to be observed. Over the course of reactions containing shales, dissolved solids were tracked to better understand how reactions with minerals in the shale impact water quality.

Consequences of variable thermal conductivity and activation energy on peristalsis in curved configuration

Here peristalsis of non-Newtonian liquid in the presence of heat and mass transfer is examined. Mathematical formulation is developed in view of viscous dissipation, variable thermal conductivity and activation energy. Lubrication approach is adopted to retain mathematical modeling in tractable form. Series solution via small Weissenberg is obtained for momentum equation while temperature and concentration equations are solved numerically via built-in shooting technique. The obtained series solutions for pressure gradient, pressure rise per wavelength, stream function, velocity and numerical solutions for temperature, concentration and rates of heat and mass transfer are validated via graphical presentations. Discussion is made in detail. It is observed from the graphical results that pressure rise per wavelength and pressure gradient have opposite behavior for Wessienberg and Johnson-Segalman fluid slip factor parameters. It is reported that due to increasing impact of activation energy parameter concentration enhances whereas opposite impact of chemical reaction parameter on concentration is noted.

Modeling Chemically Reactive Flow of Sutterby Nanofluid by a Rotating Disk in Presence of Heat Generation/Absorption

In this article we investigate the flow of Sutterby liquid due to rotating stretchable disk. Mass and heat transport are analyzed through Brownian diffusion and thermophoresis. Further the effects of magnetic field, chemical reaction and heat source are also accounted. We employ transformation procedure to obtain a system of nonlinear ODE’s. This system is numerically solved by Built-in-Shooting method. Impacts of different involved parameter on velocity, temperature and concentration are described. Velocity, concentration and temperature gradients are numerically computed. Obtained results show that velocity is reduced through material parameter. Temperature and concentration are enhanced with thermophoresis parameter.

Zinc-mediated Reversible Multimerization of Hsp31 Enhances the Activity of Holding Chaperone

Hsp31 protein, belonging to the DJ-1/ThiJ/PfpI superfamily, increases the survival of Escherichia coli under various stresses. While it was reported as a holding chaperone, Hsp31 was also shown to exhibit the glyoxalase III activity in subsequent study. Here, we describe our finding that Hsp31 undergoes a Zn+2-mediated multimerization (HMWZinc), resulting in an enhanced chaperone activity. Furthermore, it was shown that the formation of HMWZinc is reversible such that the oligomer dissociates into the native dimer by EDTA incubation. We attempted to determine the structural change involving the transition between the native dimer and HMWZinc by adding Ni+2, which is Zn+2-mimetic, producing a potential intermediate structure. An analysis of this intermediate revealed a structure with hydrophobic interior exposed, due to an unfolding of the N-terminal loop and the C-terminal β-to-α region. A treatment with hydrogen peroxide accelerated HMWZinc formation, so that the Hsp31C185E mutant rendered the formation of HMWZinc even at 45 °C. However, the presence of Zn+2 in the catalytic site antagonizes the oxidation of C185, implying a negative role. Our results suggest an unprecedented mechanism of the enhancing chaperone activity by Hsp31, in which the reversible formation of HMWZinc occurs in the presence of heat and Zn+2 ion.

Microencapsulation of pequi pulp oil by complex coacervation

Abstract Pequi pulp oil, Caryocar brasiliense, is rich in carotenoids, antioxidant compound easily oxidized by the presence of heat, light and oxygen. In order to improve its stability, pequi oil was microencapsulated by complex coacervation using gelatin and Arabic gum as encapsulating agents. Twenty formulations were prepared using a 23 central composite rotational design. The influence of temperature, stirring velocity and core material in the oil coacervation were evaluated, aiming to preserve carotenoids present in the oil. The best yield values and carotenoids content were obtained at the midpoint of the design (7.5g core, 15.000rpm and 50°C). Particles showed asymmetric distribution, with diameter ranging from 15 to 145 µm and the efficiency of the encapsulation process, obtained by the retention of oil in the microcapsule, ranged from 66.58 to 96.50%, thus demonstrating the encapsulation efficiency of this method.

A numerical investigation on ethylene glycol-titanium dioxide nanofluid convective flow over a stretching sheet in presence of heat generation/absorption

In this article, TiO2-ethylene glycol nanofluid flow over a porous stretching sheet in presence of non-uniform generation or absorption of heat and convective boundary condition is investigated. The concentration of solute is set by the means of an isothermal model of homogeneous-heterogeneous reactions. The governing equations were simplified to ordinary differential equations and solved using Runge-Kutta-Fehlberg shooting method of fifth order. Effects of different variables such as nanoparticle volume fraction, porosity variable, and Schmidt number were studied and the results are graphically presented. The results showed that the stretching rate ratio has inverse effect of velocities in both directions. According to plots, nanoparticle volume fraction as well as convective heat intensity has a direct relation with wall heat flux, in the contrary, heat generation has an inverse effect on it.

Dufour Effects on Unsteady MHD Free Convective Flow of Two Immiscible Fluid in a Horizontal Channel Under Chemical Reaction and Heat Source

The effect of Dufour on Unsteady MHD convective immiscible fluid flow passing through a horizontal channel in the presence of Heat, mass transfer, chemical reaction and Heat source consumption are studied here. The non-linear equations are solved with the appropriate boundary conditions. The governing equations of the flow are solved by a regular Perturbation technique. Then the effects of various flow parameters like Grashof numbers for heat and mass transfer, Prandtl number, Viscosity ratio, conductivity ratio, Radiative parameter, Schmidt number, Dufour effect etc. on the velocity field have been solved graphically and analyzed quantitatively.

Buoyancy-driven flow of nanofluids in an inclined enclosure containing an adiabatic obstacle with heat generation/absorption: Effects of periodic thermal conditions

The buoyancy-driven heat transfer enhancement and fluid flow of nanofluids inside inclined enclosures in the presence of heat generation/absorption effect are investigated in this paper. The bottom and top walls of the enclosure are thermally insulated, while both side walls are considered to have sinusoidal distributions of thermal boundary conditions. Two cases are considered; an enclosure containing a cold obstacle and the other one contains a cold circular cylinder. The governing equations are converted to dimensionless forms and then solved using Galerkin finite element method. Effects of the key-parameters, namely, Rayleigh number, nanoparticle volume fraction, cavity inclination angle, heat generation/absorption parameter, amplitude parameter, phase angle, size and position of the inner shapes on the contours of streamlines and isotherms as well as average Nusselt number are examined. It is found that an enclosure with a square obstacle enhances the heat transfer rate with a higher rate comparing with the circular cylinder case. Also, Considering an inclined cavity gives rate of heat transfer greater than the horizontal/vertical cavity. In addition, regardless the inner shape, the average Nusselt number is an increasing function of nanoparticle volume fraction, amplitude parameter and phase angle.

Approximate analytical solutions to nonlinear peristaltic flow with temperature-dependent viscosity parameters: Application of multi-step differential transform method (MsDTM)

This paper investigates the influence of temperature-dependent viscosity on peristaltic flow of a Newtonian fluid past a vertical asymmetric channel through a porous medium in the presence of heat ...

Radiative and magnetohydrodynamics flow of third-grade viscoelastic fluid past an isothermal inverted cone in the presence of heat generation/absorption

A mathematical analysis to investigate the non-linear, isothermal, steady state, free convection boundary layer flows of an incompressible third-grade viscoelastic fluid past an isothermal inverted cone in the presence of magnetohydrodynamic, thermal radiation, and heat generation/absorption. The transformed conservation equations for linear momentum, heat, and mass are solved numerically subject to the realistic boundary conditions using the second-order accurate implicit finite-difference Keller-box method. The numerical code is validated with the previous studies. Detailed interpretation of the computations is included. The present simulations are of interest in chemical engineering systems and solvent and low-density polymer material processing.

Free convective micropolar fluid flow and heat transfer over a shrinking sheet with heat source

The free convective micropolar fluid over a shrinking sheet in presence of heat source/sink has been studied in this paper. The method of solution involves similarity transformation. The coupled non-linear partial differential equations representing momentum and concentration and non homogeneous heat equation are reduced into set of non-linear ordinary differential equations. The transformed equations are solved by applying Runge-Kutta method followed by shooting technique. The effect of pertinent parameters characterizing the flow has been presented through the graphs and then discussed. It is found that heat source has significant effect on velocity profile and causes a decrease in the boundary layer. Angular velocity profile increases with the increasing value of material parameter. Present study showed an excellent agreement with published literature.

Unsteady Sisko magneto-nanofluid flow with heat absorption and temperature dependent thermal conductivity: A 3D numerical study

Abstract The impact of temperature dependent thermal conductivity and convective surface conditions on unsteady 3D Sisko nanofluid flow over a stretching surface is studied in the presence of heat generation/absorption and magnetic field. The numerical solution of nonlinear coupled equations has been carried out to explore the properties of different physical profiles of the fluid flow with varying of parameters. Specifically, the application of generalized Biot numbers and heat generation/absorption parameter in the sketching of temperature and concentration profiles are explored. The effect of all three parameters is noticed in the increasing order for shear thinning ( 0 n 1 ) and for shear thickening ( n > 1 ) fluids. Moreover, the influence of Biot number γ 1 on heat and mass transfer rates, are found in the enhancement and diminishing conducts respectively, in both cases of shear thinning as well as shear thickening fluids and a reverse trend is observed with the variation of Biot number γ 2 . Additionally, the present results are validated through skin friction, heat and mass transfer rate values with the comparable values in the existing previous values.

On Model for Three-Dimensional Flow of Nanofluid With Heat and Mass Flux Boundary Conditions

The present paper examines magnetohydrodynamic (MHD) three-dimensional (3D) flow of viscous nanoliquid in the presence of heat and mass flux conditions. A bidirectional nonlinearly stretching surface has been employed to create the flow. Heat and mass transfer attribute analyzed via thermophoresis and Brownian diffusion aspects. Viscous liquid is electrically conducted subject to applied magnetic field. Problem formulation is made through the boundary layer approximation under small magnetic Reynolds number. Appropriate transformations yield the strong nonlinear ordinary differential system. The obtained nonlinear system has been solved for the convergent homotopic solutions. Effects of different pertinent parameters with respect to temperature and concentration are sketched and discussed. The coefficients of skin friction and heat and mass transfer rates are computed numerically.