Fluctuation Hydrodynamics, Thermophoresis of Nanoparticles and Heat Transfer in Nanofluids

2012 ◽  
Author(s):  
Alexandr S. Dmitriev
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Temperature Gradient ◽  
Long Wavelength ◽  
Long Wave ◽  
New Type ◽  
The One ◽  
Fluid Hydrodynamics ◽  
Two Fluid

In this paper we studied in the framework of two-fluid hydrodynamics with fluctuations the behavior of nanoparticles in the liquid with temperature gradient [1, 2]. It is shown that the acoustic long-wave fluctuations are not damped in liquids (long-wavelength phonons) and leads to an additional force acting on the nanoparticles, as well as lead to the emergence of a new force of thermophoresis [3], which is proportional to the temperature in three second degree. It is also shown that such a thermophoresis force arising under the two-fluid hydrodynamics, can lead to instability of an ensemble of nanoparticles in the presence of a temperature gradient. The last effect leads to the possible merger of the nanoparticles in the form of elongated clusters. The appearance of such clusters on the one hand, leads to an increase in effective thermal conductivity of nanofluids, and secondly, appearing elongated clusters contribute to the propagation of long-wavelength phonons along of such clusters. In fact, this new type of heat transfer in nanofluids, which must be considered in addition to the Brownian motion of nanoparticles.

Numerical Simulation for Microconvection Around Nano-Particle With Brownian Motion in Liquid

2003 ◽  
Author(s):  
B. X. Wang ◽  
H. Li ◽  
X. F. Peng ◽  
L. X. Yang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Brownian Motion ◽  
Numerical Model ◽  
Temperature Gradient ◽  
Transfer Process ◽  
Heat Transfer Process ◽  
Nano Particles ◽  
Analytic Method ◽  
Nano Particle

The development of a numerical model for analyzing the effect of the nano-particles’ Brownian motion on the heat transfer is described. By using the Maxwell velocity distribution relations to calculate the most possible velocity of fluid molecules at certain temperature gradient location around the nano-particle, the interaction between fluid molecules and one single nano-particle is analyzed and calculated. Based on this, a syntonic system is proposed and the coupled effect that Brownian motion of nano-particles has on fluid molecules is simulated. This is used to formulate a reasonable analytic method, facilitating laboratory study. The results provide the essential features of the heat transfer process, contributed by micro-convection to be considered.

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.

Numerical Computation of the Effects of Brownian Motion on the Effective Thermal Conductivity of Suspensions

2007 ◽  
Author(s):  
P. E. Phelan ◽  
J. R. Pacheco
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Dimensional Space ◽  
Numerical Technique ◽  
Heat Transfer Process ◽  
Immersed Boundary ◽  
Brownian Dynamic ◽  
Dynamic Simulations ◽  
Bulk Fluid

In this paper, a numerical scheme based on the immersed boundary method is used to study the motion of nano-sized particles subjected to Brownian motion and heat transfer. Our objective is to use this numerical technique as a tool to better understand the effect that Brownian forces have on the overall heat transfer process. The conventional approach to perform Brownian dynamic simulations is based on the use of a random force in the particle motion such that the fluctuation-dissipation theorem is satisfied. Our preliminary computational results suggest an increase in the thermal conductivity of the bulk fluid. Results are presented for several particles in a two-dimensional space.

Thermal Conductivity and Specific Heat Evaluation of Tissue Using Laser

2020 ◽  
Vol 1002 ◽  
pp. 303-310
Author(s):  
Sudad Issam Younis ◽  
Haqi I. Qatta ◽  
Mohammed Jalal Abdul Razzaq ◽  
Khalid S. Shibib
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Specific Heat ◽  
Iterative Procedure ◽  
Input Data ◽  
Maximum Error ◽  
Heat Transfer Analysis ◽  
Long Wavelength ◽  
Inverse Heat Transfer

In this work, an inverse heat transfer analysis was used to determine thermal conductivity and specific heat of tissue using special iteration. A laser with a long wavelength was utilized to impose heat to the tissue. The heat that induced in the sample causes an increase in the temperature of a tissue which is measured by a thermocouple. The readings were used together with that analytically obtained from the solution of the heat equation in an iterative procedure to obtain the thermal properties of tissue. By using this method, accurate thermal conductivity and specific heat of tissue could be obtained. It was found that the maximum error in output result and the error in input data were in the same order and that there was a linear relationship between output and input errors.

Temperature-dependent effect of percolation and Brownian motion on the thermal conductivity of TiO2–ethanol nanofluids

2016 ◽  
Vol 18 (22) ◽  
pp. 15363-15368 ◽  
Author(s):  
Chien-Cheng Li ◽  
Nga Yu Hau ◽  
Yuechen Wang ◽  
Ai Kah Soh ◽  
Shien-Ping Feng
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Thermal Storage ◽  
Temperature Dependent ◽  
Dependent Effect ◽  
And Brownian Motion ◽  
Potential Applications

Ethanol-based nanofluids have attracted much attention due to the enhancement in heat transfer and their potential applications in nanofluid-type fuels and thermal storage.

On the stability of nonlinear waves coexisting with plasma beams

1975 ◽  
Vol 13 (1) ◽  
pp. 173-187 ◽  
Author(s):  
E. Infeld ◽  
G. Rowlands
Keyword(s):  
Nonlinear Wave ◽  
Growth Rates ◽  
Three Dimensional ◽  
Stationary Waves ◽  
One Dimensional ◽  
Long Wavelength ◽  
Long Wave ◽  
Set Up ◽  
The Stability ◽  
The One

In this paper we consider the stability of one-dimensional stationary waves set up by two counter-streaming beams of electrons in a background of stationary ions. The perturbations considered are long-wave in a direction perpendicular to the wave. The presence of a uniform magnetic field in the direction of the wave and the effect of a perpendicular pressure are taken into account. In the long-wavelength limit growth rates are diminished by the nonlinear wave. When the amplitude of this wave tends to its maximum value, the growth rates tend to zero. Thus the wave has a stabilizing effect for long-wave perturbations. Three- dimensional effects lead to additional instabilities which are also quenched by the nonlinear wave, but not as fast as the one-dimensional calculation indicates.

scholarly journals A method of experimental studies of heat transfer processes between industrial constructions

2018 ◽  
Vol 230 ◽  
pp. 02021
Author(s):  
Vadym Nizhnyk ◽  
Oksana Kyrychenko ◽  
Olexandr Tarasenko ◽  
Andrii Shvydenko ◽  
Serhii Hovalenkov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Flux Density ◽  
Experimental Studies ◽  
Heat Radiation ◽  
Ambient Conditions ◽  
Transfer Processes ◽  
Density Values ◽  
New Type ◽  
The One

A method of experimental study of heat transfer processes between industrial constructions during a fire was developed. Types of equipment necessary for the conduction of the experimental studies were determined. A new type of specimen to be used as the one to be studied when conducting experimental studies was developed. Installation sites of thermocouples and heat flux detector on the specimen under study are shown as layout. Installation sites of the specimens under study relative to heat radiation source were substantiated experimentally. Succession of the conduction of the experimental studies of heat transfer processes between industrial constructions during a fire was developed which consists of the following procedures: production of specimens for the studies, measurement and recording on ambient conditions, measuring of temperature and heat flux on the surface of the specimen under study, and filling 55B test fire with water and diesel fuel. It was established that average temperatures and heat flux density values as well as flame geometry should be measured when performing experimental studies.

scholarly journals On heat transfer of weakly compressible power-law flows

2017 ◽  
Vol 21 (6 Part B) ◽  
pp. 2709-2718
Author(s):  
Botong Li ◽  
Liangliang Zhu ◽  
Liancun Zheng ◽  
Wei Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Temperature Gradient ◽  
Power Law ◽  
Conductivity Model ◽  
Weakly Compressible ◽  
Power Law Fluids ◽  
Momentum And Heat Transfer ◽  
Thermal Conductivity Model ◽  
Dilatant Fluid

This paper completes a numerical research on steady momentum and heat transfer in power-law fluids in a channel. Weakly compressible laminar fluids are studied with no slip at the walls and uniform wall temperatures. The full governing equations are solved by continuous finite element method. Three thermal conductivity models are adopted in this paper, that is, constant thermal conductivity model, thermal conductivity varying as a function of temperature gradient, and a modified temperature-gradient-dependent thermal conductivity model. The results are compared with each other and the physical characteristics for values of parameters are also discussed in details. It is shown that the velocity curve from the solution becomes straight at higher power-law index. The effects of Reynolds numbers on the dilatant fluid and the pseudo-plastic look similar to each other and their trends can be easily predicted. Furthermore, for different models, the temperature curves also present pseudo-plastic and dilatant properties.

Heat-Transfer Stability of Porous Fibrous Composition under Different Condition

2014 ◽  
Vol 1004-1005 ◽  
pp. 557-561
Author(s):  
Yu Juan Wang ◽  
Hai Zhen Chen ◽  
Jin Mei Wang ◽  
Mei Zhen Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Process ◽  
Surface Condition ◽  
Transfer Model ◽  
Unsteady Heat Transfer ◽  
One Dimensional ◽  
The One ◽  
Thermal Difference ◽  
Key Parameter

In this paper, the influences of different conditions on heat-transfer stability of porous fibrous composition were analyzed by the one-dimensional unsteady heat transfer model. It was resulted that the surface condition of composition was key parameter for heat performance during different thermal process. Great humidity and thermal difference caused the heat transfer fluctuating of material covering, and then changed the thermal conductivity. For the insulation materials under low temperature, the heat performance was sharply fluctuated nearby 0°C.

scholarly journals The influence of pressure on the thermal conductivity of liquid He ll

1939 ◽  
Vol 171 (945) ◽  
pp. 242-250 ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Transfer ◽  
Heat Flow ◽  
Low Temperature ◽  
Temperature Gradient ◽  
Standard Method ◽  
The Other ◽  
Surface Films ◽  
Very High

The unusual characteristics of heat transfer in liquid He II have been reported in several recent papers. The very high thermal conductivity of the low-temperature modification of liquid helium was first noted by Keesom and Keesom (1935). It was then found by Allen, Peierls and Uddin (1937) and subsequently verified by Keesom, Keesom and Saris (1938) that the rate of transfer of heat varied with the temperature gradient. The discovery of the momentum transfer accompanying heat flow in He II which was made by Allen and Jones (1938) and the work on mobile surface films of the liquid done by Daunt and Mendelssohn (1938) show that a large part of the heat must be carried by some form of mass transfer. Several ideas and theories to explain the phenomena have been put forward by Kapitza (1938), Jones (1938), Michels, Bijl and de Boer (1938), Tisza (1938) and Keesom and Taconis (1938). The experimental evidence is as yet too meagre to prove or disprove any of the theories. It was with the intention of adding to the data already known concerning the properties of liquid He II that the present research was undertaken. The apparatus which was used is shown in fig. 1. The thermal conductivity was measured by a standard method. A constant supply of heat was supplied to one end of a long capillary containing liquid He II, and the other end was maintained at the constant temperature of the He II bath. Temperatures were observed at two points along the capillary.

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