Numerical Solution of Transient Heat Conduction Equation for Heat-Treatable Alloys Whose Thermal Properties Change With Time and Temperature

1977 ◽  
Vol 99 (3) ◽  
pp. 471-478 ◽  
Author(s):  
K. Farnia ◽  
J. V. Beck
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Differential Equations ◽  
Numerical Solution ◽  
Precipitation Hardening ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Transient Heat Conduction ◽  
Computer Assisted ◽  
Al 2024

Changes in microstructure occur in as-received aluminum alloy (Al-2024-T351) when it is subjected to elevated temperatures (150–260°C). These changes, which are called precipitation hardening, in turn influence the thermal properties, making them time as well as temperature dependent. A computer-assisted transient experimental procedure has been developed to determine the values of thermal conductivity of as-received Al-2024-T351 under the influence of precipitation-hardening. Based on isothermal experimental data and related algebraic modeling of the thermal conductivity, a mathematical model in the form of two differential equations is proposed. Instantaneous values of volume fraction of precipitate and thermal conductivity can be predicted using this model. A method for the simultaneous numerical solution of the partial differential equation of conduction and the proposed differential equations of precipitation are also given. The influence of precipitation—hardening on temperature distribution and on values of thermal conductivity is shown graphically for several cases involving the Al-2024-T351 material.

Effect of Coating on the Thermal Conductivities of Diamond/Cu Composites Prepared by Spark Plasma Sintering (SPS)

2014 ◽  
Vol 722 ◽  
pp. 25-29 ◽  
Author(s):  
Q.L. Che ◽  
X.K. Chen ◽  
Y.Q. Ji ◽  
Y.W. Li ◽  
L.X. Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Theoretical Prediction ◽  
Volume Fraction ◽  
Interface Reaction ◽  
Copper Matrix ◽  
Bonding Force ◽  
Ti Alloys ◽  
Plasma Sintering ◽  
Spark Plasma

The carbide forming is proposed to improve interfacial bonding between diamond particles and copper-matrix for diamond/copper composites. The volume fraction of diamond and minor titanium are optimized. The microstructures, thermal properties, interface reaction production and its effect of minor titanium on the properties of the composites are investigated. The results show that the bonding force and thermal conductivity of the diamond/Cu-Ti alloys composites is much weaker and lower than that of the coated-diamond/Cu. the thermal conductivity of coated-60 vol. % diamond/Cu composites is 618 W/m K which is 80 % of the theoretical prediction value. The high thermal conductivity has been achieved by forming the titanium carbide at diamond/copper interface to gain a good interface.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

Thermal properties of kinetic spray Al–SiC metal-matrix composite

2003 ◽  
Vol 18 (4) ◽  
pp. 855-860 ◽  
Author(s):  
Gary L. Eesley ◽  
Alaa Elmoursi ◽  
Nilesh Patel
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Properties ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Spray Deposition ◽  
Deposition Process ◽  
Matrix Composites ◽  
Kinetic Spray ◽  
Compositional Variations

Kinetic spray deposition provides a new means for producing composite materials with tailored physical properties. We report on measurements of the thermal conductivity and thermal-expansion coefficient for several compositional variations of kinetically sprayed Al–SiC metal-matrix composites. As a result of the deposition process, inclusion of SiC particles saturates in the 30–40% volume fraction range.

Effects of Variable Viscosity and Thermal conductivity on Natural-Convection of Nanofluids Past a Vertical Plate in Porous Media

2013 ◽  
Vol 30 (3) ◽  
pp. 265-275 ◽  
Author(s):  
A. Noghrehabadi ◽  
M. Ghalambaz ◽  
A. Ghanbarzadeh
Keyword(s):  
Thermal Conductivity ◽  
Brownian Motion ◽  
Natural Convection ◽  
Differential Equations ◽  
Vertical Plate ◽  
Volume Fraction ◽  
Variable Viscosity ◽  
Increase With Increase ◽  
Dimensional Parameters ◽  
Brownian Motion And Thermophoresis

ABSTRACTThe effects of variable viscosity and thermal conductivity on the natural convection heat transfer over a vertical plate embedded in a porous medium saturated by a nanofluid are investigated. In the nanofluid model, a gradient of nanoparticles concentration because of Brownian motion and thermophoresis forces is taken into account. The nanofluid viscosity and the thermal conductivity are assumed as a function of local nanoparticles volume fraction. The appropriate similarity variables are used to convert the governing partial differential equations into a set of highly coupled nonlinear ordinary differential equations, and then, they numerically solved using the Runge-Kutta-Fehlberg method. The practical range of non- dimensional parameters is discussed. The results show that the range of Lewis number as well as Brownian motion and thermophoresis parameters which were used in previous studies should be reconsidered. The effect of non-dimensional parameters on the boundary layer is examined. The results show that the reduced Nusselt number would increase with increase of viscosity parameter and would decrease with increase of thermal conductivity parameter.

Thermal properties of nanocrystalline Al composites reinforced by AlN nanoparticles

2009 ◽  
Vol 24 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Y.Q. Liu ◽  
H.T. Cong ◽  
H.M. Cheng
Keyword(s):  
Thermal Properties ◽  
Room Temperature ◽  
Significant Contribution ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
High Tc ◽  
Percolation Behavior ◽  
Potential Applications ◽  
Electronic Packaging Material

To explore potential applications of nanocomposites for microelectronic packaging, the thermal properties were investigated on newly developed nanocrystalline Al composites reinforced by AlN nanoparticles. It was found that the thermal conductivity (TC) is reduced with increasing AlN volume fraction (Vp), since connectivity of Al matrix is decreased by introduction of the nanoparticles. Although AlN nanoparticles introduce thermal resistance, they still have significant contribution to the TC of the composite as high-TC inclusion. Particularly, a percolation behavior of AlN nanoparticles is thought to occur with the threshold at 23–30%. Measurements at elevated temperatures (∼500 °C) show almost no distinct degradation of TC relative to room temperature. Moreover, the coefficient of thermal expansion (CTE) is remarkably lowered as Vp increases, e.g., from 26 × 10−6 to 13.9 × 10−6 K−1, by raising Vp to 39%. Therefore, the nanocomposites may be applicable as electronic packaging material, due to the combination of acceptable TC and low CTE.

Thermal Properties of Si Mechanically Alloyed with FeSi2 and CrSi2

2015 ◽  
Vol 799-800 ◽  
pp. 207-211
Author(s):  
Konstantin N. Galkin ◽  
Andrey Usenko ◽  
Andrey Voronin ◽  
Dmitriy Moskovskikh ◽  
Andrey Korotitskiy ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Size Effect ◽  
Band Gap ◽  
Lattice Thermal Conductivity ◽  
Volume Fraction ◽  
Reference Sample ◽  
The Other ◽  
Mechanically Alloyed ◽  
Silicon Structures

Thermal properties of Si mechanically alloyed with FeSi2 and CrSi2 were characterized for the samples with different volume fraction of the disilicides. An anomalously low thermal conductivity observed in the FeSi2-doped samples was ascribed to an enhanced porosity of the samples which triggered the size effect on the lattice thermal conductivity reported previously for nanomeshed and “holey” silicon structures. It was also found that alloying of Si with FeSi2 led to a reduction of thermal conductivity as compared to the reference sample of pure Si prepared under the same conditions. On the other hand, alloying of Si with CrSi2 resulted in an increase in the thermal conductivity as compared to the reference sample of pure Si. The observed trends in the thermal conductivity were ascribed to the formation of impurity levels in the band gap.

scholarly journals Heat Transfer Analysis of MHD Water Functionalized Carbon Nanotube Flow over a Static/Moving Wedge

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Waqar A. Khan ◽  
Richard Culham ◽  
Rizwan Ul Haq
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Differential Equations ◽  
Skin Friction ◽  
Volume Fraction ◽  
Heat Transfer Analysis ◽  
Published Data ◽  
Nusselt Numbers ◽  
Moving Wedge ◽  
The Impact

The MHD flow and heat transfer from water functionalized CNTs over a static/moving wedge are studied numerically. Thermal conductivity and viscosity of both single and multiple wall carbon nanotubes (CNTs) within a base fluid (water) of similar volume are investigated to determine the impact of these properties on thermofluid performance. The governing partial differential equations are converted into nonlinear, ordinary, and coupled differential equations and are solved using an implicit finite difference method with quasi-linearization techniques. The effects of volume fraction of CNTs and magnetic and wedge parameters are investigated and presented graphically. The numerical results are compared with the published data and are found to be in good agreement. It is shown that the magnetic field reduces boundary layer thickness and increases skin friction and Nusselt numbers. Due to higher density and thermal conductivity, SWCNTs offer higher skin friction and Nusselt numbers.

Structural and Thermal Properties of Hot Pressed Cu/C Matrix Composites Materials Used for the Thermal Management of High Power Electronic Devices

2007 ◽  
Vol 534-536 ◽  
pp. 1505-1508 ◽  
Author(s):  
Pierre Marie Geffroy ◽  
Jean François Silvain
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Carbon Fibers ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Copper Matrix ◽  
Matrix Composites ◽  
Porosity Level ◽  
Materials Used ◽  
Short Carbon

In order to obtain materials for electronic applications that exhibit both excellent thermal conductivity and low coefficient of thermal expansion (CTE), copper matrix composites have been reinforced by short high modulus graphite fibers. The lack of fiber/matrix interaction prevents any degradation of the carbon reinforcement during the elaboration steps and the normal use of these materials. Elaboration conditions, such as mixing conditions of the short carbon fibers and the copper powder, dimension and shape of the two powders, and finally densification atmosphere, temperature, pressure and time, have been optimized. Main parameters involved in the thermal properties of the Cu/C composite materials have been analyzed and adjusted. CTE is mainly related with the carbon volume fraction; CTE ranging from 9 to 13 10-6/°C can be reproductively obtained with carbon volume fraction ranging from 50% to 20%. Thermal conductivity properties are more complex and are linked mainly with 1) the porosity level inside the material, and 2) the orientation, properties and volume fraction of the carbon fibers. For short carbon fibers, in plane thermal conductivity ranging from 200 to 550 W/mK have been reproductively measured associated with thermal conductivity through-thickness ranging from 150 to 300 W/mK.

scholarly journals Exploration of Aluminum and Titanium Alloys in the Stream-Wise and Secondary Flow Directions Comprising the Significant Impacts of Magnetohydrodynamic and Hybrid Nanofluid

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 679 ◽  
Author(s):  
Kottakkaran Sooppy Nisar ◽  
Umair Khan ◽  
Aurang Zaib ◽  
Ilyas Khan ◽  
Dumitru Baleanu
Keyword(s):  
Thermal Conductivity ◽  
Differential Equations ◽  
Volume Fraction ◽  
Cross Flow ◽  
Hybrid Nanofluid ◽  
Nonlinear Odes ◽  
Soret Number ◽  
Flow Directions ◽  
Titanium Alloy Ti6al4v ◽  
Dufour Number

This exploration examines the nonlinear effect of radiation on magnet flow consisting of hybrid alloy nanoparticles in the way of stream-wise and cross flow. Many experimental, as well as theoretical explorations, demonstrated that the thermal conductivity of the regular liquid increases by up to 15 to 40% when nanomaterials are mixed with the regular liquid. This change of the thermal conductivity of the nanoliquid depends on the various characteristics of the mixed nanomaterials like the size of the nanoparticles, the agglomeration of the particles, the volume fraction, etc. Researchers have used numerous nanoparticles. However, we selected water-based aluminum alloy (AA7075) and titanium alloy (Ti6Al4V) hybrid nanomaterials. This condition was mathematically modeled by capturing the Soret and Dufour impacts. The similarity method was exercised to change the partial differential equations (PDEs) into nonlinear ordinary differential equations (ODEs). Such nonlinear ODEs were worked out numerically via the bvp4c solver. The influences of varying the parameters on the concentration, temperature, and velocity area and the accompanying engineering quantities such as friction factor, mass, and heat transport rate were obtained and discussed using graphs. The velocity declines owing to nanoparticle volume fraction in the stream-wise and cross flow directions in the first result and augment in the second result, while the temperature and concentration upsurge in the first and second results. In addition, the Nusselt number augments due to the Soret number and declines due to the Dufour number in both results, whereas the Sherwood number uplifts due to the Dufour number and shrinks due to the Soret number in both results.

Comparison of Conductivity of Al2O3 Nanofluids between Experiments and Maxwell Model

2013 ◽  
Vol 668 ◽  
pp. 571-574
Author(s):  
Jin Ze Yu ◽  
Bin Liu ◽  
Zhen Liang Li
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Mass Fraction ◽  
Base Fluid ◽  
Volume Fraction ◽  
Critical Role ◽  
Maxwell Model ◽  
Nano Particle ◽  
Coefficient Of Thermal Conductivity ◽  
Nano Fluids

The thermal properties of nano-fluids are affected by many factors. The effect of the diameter, mass fraction and volume fraction of Al2O3 in water on the thermal conductivity was measured by the method of hotwire. The diameter of nano-particle of Al2O3 was 10nm, 20nm, 50nm, 100nm and 500nm respectively. The mass fraction of Al2O3 in water was 10%, 12%, 15% and 20%. The results show that the diameter of the particle plays a critical role on thermal properties of the base fluid. And for the mass fraction, it will increase the thermal conductivity of the base fluid. When the size is more than 100nm, the coefficient of thermal conductivity is increased rapidly. Compared with the results calculated by the Maxwell model, the conductivity of the nanofulid with a diameter less than 10nm is consistent with the model’s result. And with the increasing of the diameter o f the nanoparticle, the deviation of the conductivity will also increase compared with the model’s results.

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