Impact of Stefan blowing and magnetic dipole on bio-convective flow of Maxwell nanofluid over a stretching sheet

2021 ◽  
pp. 095440892110581
Author(s):  
A. Alhadhrami ◽  
Hassan A. H. Alzahrani ◽  
B. M. Prasanna ◽  
N. Madhukeshwara ◽  
K. C. Rajendraprasad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Brownian Motion ◽  
Magnetic Dipole ◽  
Stretching Sheet ◽  
High Heat ◽  
Hard Drives ◽  
Linear System Of Equations ◽  
High Heat Transfer ◽  
Non Linear System ◽  
The Impact

The features of ferromagnetic fluids make it supportive for an extensive usage in loudspeakers, magnetic resonance imaging, computer hard drives, directing of magnetic drug and magnetic hyperthermia. Owing to all such potential applications, the current investigation is to understand the relationship between the thermal distribution, magnetic field and resulting fluid flow of Maxwell liquid over a stretching sheet. Investigation of thermal energy and concentration is carried out in the presence of thermal radiation, non-uniform heat sink/source, chemical reaction, Stefan blowing, magnetic dipole, thermophoresis and Brownian motion. Also, microorganisms are considered just to stabilize the suspended nanoparticles. Boundary layer approximation is employed during mathematical derivation. Based on a new constitutive relation, the governing equations are formulated and are reduced into a coupled non-linear system of equations using appropriate transformations. Further, these equations are solved numerically using fourth-order Runge–Kutta method with shooting technique. The impact of involved parameters is discussed and analysed graphically. Outcomes disclose that Newtonian liquid shows high heat transfer when compared to non-Newtonian (Maxwell) liquid for increased values of Brownian motion and thermophoresis parameters. Increased values of Peclet number declines the rate of gyrotactic microorganisms. Finally, an increase in Brownian and thermophoresis motion parameters declines the rate of heat transfer.

Possible Mechanisms for Thermal Conductivity Enhancement in Nanofluids

2006 ◽  
Author(s):  
Amit Gupta ◽  
Xuan Wu ◽  
Ranganathan Kumar
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Brownian Dynamics ◽  
Lattice Vibration ◽  
Experimental Studies ◽  
High Heat ◽  
Conductivity Enhancement ◽  
High Heat Transfer ◽  
Dynamics Simulations

This study discusses the merits of various physical mechanisms that are responsible for enhancing the heat transfer in nanofluids. Experimental studies have cemented the claim that ‘seeding’ liquids with nanoparticles can increase the thermal conductivity of the nanofluid by up to 40% for metallic and oxide nanoparticles dispersed in a base liquid. Experiments have also shown that the rise in conductivity of the nanofluid is highly dependent on the size and concentration of the nanoparticles. On the theoretical side, traditional models like Maxwell or Hamilton-Crosser models cannot explain this unusually high heat transfer. Several mechanisms have been postulated in the literature such as Brownian motion, thermal diffusion in nanoparticles and thermal interaction of nanoparticles with the surrounding fluid, the formation of an ordered liquid layer on the surface of the nanoparticle and microconvection. This study concentrates on 3 possible mechanisms: Brownian dynamics, microconvection and lattice vibration of nanoparticles in the fluid. By considering two nanofluids, copper particles dispersed in ethylene glycol, and silica in water, it is determined that translational Brownian motion of the nanoparticles, presence of an interparticle potential and the microconvection heat transfer are mechanisms that play only a smaller role in the enhancement of thermal conductivity. On the other hand, the lattice vibrations, determined by molecular dynamics simulations show a great deal of promise in increasing the thermal conductivity by as much as 23%. In a simplistic sense, the lattice vibration can be regarded as a means to simulate the phononic transport from solid to liquid at the interface.

scholarly journals Analysis of Magnetic Properties of Nano-Particles Due to a Magnetic Dipole in Micropolar Fluid Flow over a Stretching Sheet

Coatings ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 170 ◽  
Author(s):  
Liaqat Ali ◽  
Xiaomin Liu ◽  
Bagh Ali ◽  
Saima Mujeed ◽  
Sohaib Abdal ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Differential Equations ◽  
Magnetic Dipole ◽  
Stretching Sheet ◽  
Nano Particles ◽  
Boundary Parameter ◽  
The Impact

This article explores the impact of a magnetic dipole on the heat transfer phenomena of different nano-particles Fe (ferromagnetic) and Fe3O4 (Ferrimagnetic) dispersed in a base fluid ( 60 % water + 40 % ethylene glycol) on micro-polar fluid flow over a stretching sheet. A magnetic dipole in the presence of the ferrities of nano-particles plays an important role in controlling the thermal and momentum boundary layers. The use of magnetic nano-particles is to control the flow and heat transfer process through an external magnetic field. The governing system of partial differential equations is transformed into a system of coupled nonlinear ordinary differential equations by using appropriate similarity variables, and the transformed equations are then solved numerically by using a variational finite element method. The impact of different physical parameters on the velocity, the temperature, the Nusselt number, and the skin friction coefficient is shown. The velocity profile decreases in the order Fe (ferromagnetic fluid) and Fe3O4 (ferrimagnetic fluid). Furthermore, it was observed that the Nusselt number is decreasing with the increasing values of boundary parameter ( δ ) , while there is controversy with respect to the increasing values of radiation parameter ( N ) . Additionally, it was observed that the ferromagnetic case gained maximum thermal conductivity, as compared to ferrimagnetic case. In the end, the convergence of the finite element solution was observed; the calculations were found by reducing the mesh size.

Numerical Study of the Heat Transfer in Micro Gas Turbines

2006 ◽  
Vol 129 (4) ◽  
pp. 835-841 ◽  
Author(s):  
T. Verstraete ◽  
Z. Alsalihi ◽  
R. A. Van den Braembussche
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Numerical Study ◽  
Three Dimensional ◽  
High Heat ◽  
Large Temperature ◽  
Radial Compressor ◽  
Micro Gas Turbine ◽  
High Heat Transfer ◽  
The Impact

This paper presents a numerical investigation of the heat transfer inside a micro gas turbine and its impact on the performance. The large temperature difference between turbine and compressor in combination with the small dimensions results in a high heat transfer causing a drop in efficiency of both components. Present study aims to quantify this heat transfer and to reveal the different mechanisms that contribute to it. A conjugate heat transfer solver has been developed for this purpose. It combines a three-dimensional (3D) conduction calculation inside the rotor and the stator with a 3D flow calculation in the radial compressor, turbine and gap between stator and rotor. The results for micro gas turbines of different size and shape and different material characteristics are presented and the impact on performance is evaluated.

Influence of the Impact Angle and the Gravity Direction on Heat Transfer during the Cooling of a Cylinder by a Free Planar Subcooled Impinging Jet

2013 ◽  
Vol 554-557 ◽  
pp. 1530-1538 ◽  
Author(s):  
Sylvain Devynck ◽  
Sabine Denis ◽  
Jean Pierre Bellot ◽  
Guillaume Maigrat ◽  
Michel Varlez ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Velocity Ratio ◽  
Temperature Drop ◽  
Impinging Jet ◽  
High Heat ◽  
Water Jet ◽  
Subcooled Water ◽  
High Heat Transfer ◽  
The Impact ◽  
Transfer Mechanisms

Cooling from impinging jet is nearly compulsory in steel industry processing especially in Run Out Table processing and steel tubes production because of the high heat transfer rates provided by the boiling of the subcooled water jet. As far as metallurgical phase transformations, residual stresses and deformations in the workpiece are concerned, the temperature drop during cooling must be perfectly controlled thanks to a fully understanding of the heat transfer mechanisms. In a previous study [1] the effect of surface to jet velocity ratio on heat transfer has been characterized and it has been shown that this parameter has a significant influence on shoulder of flux collapse. In order to understand the effect of more industrial quench process parameters, an innovative experimental quenching device has been designed and built. It allowed us to make heat transfer measurements at the surface of a hot nickel cylinder impinged by a subcooled water jet, according to several angles of impact and three jet directions against gravity. The results clearly highlight an effect of these two parameters on the heat transfer mechanisms at the surface of the tube. These results allow a better understanding of the origins of temperature heterogeneities inside the tube during the quench.

Numerical Study of the Heat Transfer in Micro Gasturbines

2006 ◽  
Author(s):  
T. Verstraete ◽  
Z. Alsalihi ◽  
R. A. Van den Braembussche
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Numerical Investigation ◽  
Conjugate Heat Transfer ◽  
Numerical Study ◽  
High Heat ◽  
3D Flow ◽  
Radial Compressor ◽  
High Heat Transfer ◽  
The Impact

This paper presents a numerical investigation of the heat transfer inside a micro gasturbine and its impact on the performance. The high temperature difference between turbine and compressor in combination with the small dimensions results in a high heat transfer causing a drop in efficiency of both components. Present study aims to quantify this heat transfer and to reveal the different mechanisms that contribute to it. A conjugate heat transfer solver has been developed for this purpose. It combines a 3D conduction calculation inside the rotor and the stator with a 3D flow calculation in the radial compressor, turbine and gap between stator and rotor. The results for micro gasturbines of different size and shape and different material characteristics are presented and the impact on performance is evaluated.

Heat Transfer of Falling Film Flowing Around a Horizontal Tube With Nanofluids

2009 ◽  
Author(s):  
Binglu Ruan ◽  
Anthony M. Jacobi ◽  
Liansheng Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Horizontal Tube ◽  
High Heat ◽  
Working Fluid ◽  
Sodium Dodecylbenzene Sulfonate ◽  
Falling Film ◽  
High Heat Transfer ◽  
High Heat Transfer Coefficient ◽  
The Impact

Due to its high heat transfer coefficient and low working fluid inventory, the horizontal-tube, falling-film heat exchanger finds wide application as an absorber, condenser and evaporator. Recent advances in nanotechnology suggest the use of nanofluids in heat exchangers. Some researchers find an enhanced heat transfer with nanofluids, while others report no enhancement or a deleterious effect on heat transfer when applying nanoparticles in the working fluids. In the current work, the thermal conductivity and kinematic viscosity of aqueous alumina nanofluids are measured at concentrations of 0 vol%, 0.05 vol%, 0.5 vol%, 1 vol% (with and without sodium dodecylbenzene sulfonate, SDBS), and 2 vol%. For these nanofluids, the impact of nanoparticles on thermal conductivity and viscosity is small (less than 5% for thermal conductivity and 13% for viscosity). The heat transfer characteristics of these nanofluids are measured and compared to predictions from the literature for conventional fluids. The falling-film heat transfer for these nanofluids is in good agreement with predictions, and no unusual heat transfer enhancement is observed in the present studies. Although the findings with water-alumina nanofluids are not encouraging with respect to heat transfer, the results extend nanofluid data to a new type of flow and may help improve our understanding of nanofluid behavior. Moreover, this work provides a basis for further work on falling-film nanofluids.

scholarly journals Experimental Investigation of the Flow and Heat Transfer Characteristics in Microchannel Heat Exchangers with Reentrant Cavities

Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 403 ◽  
Author(s):  
Binghuan Huang ◽  
Haiwang Li ◽  
Tiantong Xu
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Volume Ratio ◽  
High Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
The Impact

The application of microchannel heat exchangers is of great significance in industrial fields due to their advantages of miniaturized scale, large surface-area-to-volume ratio, and high heat transfer rate. In this study, microchannel heat exchangers with and without fan-shaped reentrant cavities were designed and manufactured, and experiments were conducted to investigate the flow and heat-transfer characteristics. The impact rising from the radius of reentrant cavities, as well as the Reynolds number on the heat transfer and the pressure drop, is also analyzed. The results indicate that, compared with straight microchannels, microchannels with reentrant cavities could enhance the heat transfer and, more importantly, reduce the pressure drop at the same time. For the ranges of parameters studied, increasing the radius of reentrant cavities could augment the effect of pressure-drop reduction, while the corresponding variation of heat transfer is complicated. It is considered that adding reentrant cavities in microchannel heat exchangers is an ideal approach to improve performance.

scholarly journals Effect of Magnetohydrodynamics on Heat Transfer Behaviour of a Non-Newtonian Fluid Flow over a Stretching Sheet under Local Thermal Non-Equilibrium Condition

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 264
Author(s):  
Konduru Sarada ◽  
Ramanahalli J. Punith Gowda ◽  
Ioannis E. Sarris ◽  
Rangaswamy Naveen Kumar ◽  
Ballajja C. Prasannakumara
Keyword(s):  
Heat Transfer ◽  
Stretching Sheet ◽  
Magnetic Parameter ◽  
Solid Phase ◽  
Fluid Phase ◽  
High Heat ◽  
Temperature Profiles ◽  
High Heat Transfer ◽  
Two Dimensional Flow ◽  
Non Equilibrium

A mathematical model is proposed to describe the flow, heat, and mass transfer behaviour of a non-Newtonian (Jeffrey and Oldroyd-B) fluid over a stretching sheet. Moreover, a similarity solution is given for steady two-dimensional flow subjected to Buongiorno’s theory to investigate the nature of magnetohydrodynamics (MHD) in a porous medium, utilizing the local thermal non-equilibrium conditions (LTNE). The LTNE model is based on the energy equations and defines distinctive temperature profiles for both solid and fluid phases. Hence, distinctive temperature profiles for both the fluid and solid phases are employed in this study. Numerical solution for the nonlinear ordinary differential equations is obtained by employing fourth fifth order Runge–Kutta–Fehlberg numerical methodology with shooting technique. Results reveal that, the velocity of the Oldroyd-B fluid declines faster and high heat transfer is seen for lower values of magnetic parameter when compared to Jeffry fluid. However, for higher values of magnetic parameter velocity of the Jeffery fluid declines faster and shows high heat transfer when compared to Oldroyd-B fluid. The Jeffery liquid shows a higher fluid phase heat transfer than Oldroyd-B liquid for increasing values of Brownian motion and thermophoresis parameters. The increasing values of thermophoresis parameter decline the liquid and solid phase heat transfer rate of both liquids.

Experimental and Numerical Study on Impingement Heat Transfer and Flow Characteristics on a Semicircular Ribbed Target Surface

2021 ◽  
Author(s):  
Wang-Hao-Tai Kang ◽  
Hui-Ren Zhu
Keyword(s):  
Heat Transfer ◽  
Flow Resistance ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Target Surface ◽  
High Heat ◽  
Transfer Effect ◽  
High Heat Transfer ◽  
Special Cases ◽  
The Impact

Abstract Impact cooling is an effective way to enhance heat transfer, especially in the gas turbine blades. In the leading edge of the blade where has the high heat load, jet impingement cooling is widely used due to its high heat transfer characteristic in stagnation region. The focus is on finding a cooling structure that can improve the heat transfer effect of the internal impact structure at the leading edge without increasing the internal flow resistance. In this paper, using transient liquid crystal experiments researches for the flow and heat transfer characteristics of a semi-circular structure, which is simplified from the real blade leading edge ’s inside surface and have different rib structures. This paper studies five cases:no rib, round-shaped raised structure, oblique rib, round-shaped raised structure and oblique rib and span-wise rib and arc rib to find their heat transfer and flow characteristics. Some rib-shaped protrusion has three heights, which are 30%, 50%, 70% of the impact distance H. Experimental conditions of Reynolds number are Re = 10000, 15000, 20000, 25000, 30000. The experimental verification results show that the internally strengthened heat transfer structures studied in this paper can improve the heat transfer effect of the leading edge array of the turbine blade impact target surface without increasing the flow resistance. The structure with both oblique ribs and round-shaped raised structures has the highest surface average Nusselt number of the target plate and the lowest discharge coefficient of the channel. The structure with both span-wise ribs and arc ribs has a staggered high heat transfer area distribution, which can maybe use in some special cases.

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

2020 ◽  
pp. 095441002096469
Author(s):  
Weijie Wang ◽  
Shaopeng Lu ◽  
Hongmei Jiang ◽  
Qiusheng Deng ◽  
Jinfang Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
High Heat ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Cavity Depth ◽  
High Heat Transfer ◽  
Blade Tip ◽  
High Heat Transfer Coefficient

Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

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