Thermal Conductivity Determination of Ga-In Alloys for Thermal Interface Materials Design

Thermal interface material (TIM) that exists in a liquid state at the service temperature enables efficient heat transfer across two adjacent surfaces in electronic applications. In this work, the thermal conductivities of different phase regions in the Ga-In system at various compositions and temperatures are measured for the first time. A modified comparative cut bar technique is used for the measurement of the thermal conductivities of GaxIn1−x (x = 0, 0.1, 0.214, 0.3, and 0.9) alloys at 40, 60, 80, and 100 °C, the temperatures commonly encountered in consumer electronics. The thermal conductivity of liquid and semi-liquid (liquid + β) Ga-In alloys are higher than most of the TIM’s currently used in consumer electronics. These measured quantities, along with the available experimental data from literature, served as input for the thermal conductivity parameter optimization using the CALPHAD (calculation of phase diagrams) method for pure elements, solution phase, and two-phase region. A set of self-consistent parameters for the description of the thermal conductivity of the Ga-In system is obtained. There is good agreement between the measured and calculated thermal conductivities for all of the phases. Due to their ease of manufacturing and high thermal conductivity, liquid/semi-liquid Ga-In alloys have significant potential for TIM in consumer electronics.

Heat transfer enhancement of hybrid nanofluids over porous cone

The nanofluid is most advantageous to enhance the heat efficiency of base fluid by submerging solid nanoparticles in it. The metals, oxides, and carbides are helpful to improve the heat transfer rate. In the present analysis, the role of the slip phenomenon in the radiative flow of hybrid nanoliquid containing SiO2 silicon dioxide and CNTs over in the porous cone is scrutinized. The behavior of the magnetic field, thermal conductivity, and thermal radiation are examined. Here the base fluid ethylene glycol water (C2H6O2−H2O) is used. Accepting similarity transformation converts the controlling partial differential equations (PDEs) into ordinary differential equations (ODEs). The numerical solution is obtained by utilizing the Lobatto-IIIa method. The significant physical flow parameters are discussed by utilizing tables and graphs. Final remarks are demonstrating the velocity profile is declined via higher magnetic parameter while boosted up for nanoparticles volume fraction. Furthermore, the thermal profile is enriching via thermal conductivity parameter, radiation parameter, and nanoparticles volume fraction.

Transient Performance and Melt Front Characterization of Phase Change Materials

Thermal management systems are often over-designed for average use in order to handle spikes in heat generation, which increases the spatial and financial requirements. One way to mitigate this is via the use of phase change materials (PCMs) as thermal buffers and storage media. This paper examines the melt front behavior of a common solid to liquid PCM, paraffin, experimentally and numerically. A 16 cm3 fully enclosed melting chamber was designed and constructed to observe the melt behavior via IR imaging. The chamber applies a constant temperature heat flux to one end of the sample and a constant temperature cold boundary on the other. ARL ParaPower was used for the numerical simulation. This tool models the convection in liquid PCM as an effective thermal conductivity parameter. The MATLAB-based program offers faster computation times than high fidelity commercial FEA tools. The experimental and numerical data are then compared via a custom MATLAB script which identifies the melt front and outputs the position and velocity over time for each test case. It was concluded that ParaPower adequately depicts the melt front behavior under this set of experimental conditions. This work enables future studies using the IR-transparent melt chamber designed herein.

Entropy generation analysis for peristalsis of magneto Jeffrey materials

This article communicates peristalsis of Jeffrey material in curved geometry. Here, material has temperature-dependent thermal conductivity and viscosity. Mathematical modeling of an inclined magnetic field in curved configuration has been presented in this article. Irreversibility effects have been analyzed through entropy generation. Slip conditions are entertained both for velocity and thermal fields. Problem is first reduced in wave frame and then lubrication approach has been utilized. Numerical solution of dimensionless problem is obtained and important parameters of curiosity are examined. It is noticed that velocity enhances for higher viscosity whereas temperature decreases for higher thermal conductivity coefficient. Velocity of the flow is maximum for inclination of magnetic field to be zero and it is minimum for [Formula: see text] Heat transfer parameter enhances both for thermal conductivity parameter and Hartmann number. Temperature is high for curved configuration when compared with straight channel. It is observed that entropy remains unchanged in center of the channel and it is maximum near the channel walls. Entropy generation decays near the channel walls by higher viscosity and thermal conductivity parameters. However, entropy is more for higher inclination of magnetic field.

Numerical study of nano-biofilm stagnation flow from a nonlinear stretching/shrinking surface with variable nanofluid and bioconvection transport properties

A mathematical model is developed for stagnation point flow toward a stretching or shrinking sheet of liquid nano-biofilm containing spherical nano-particles and bioconvecting gyrotactic micro-organisms. Variable transport properties of the liquid (viscosity, thermal conductivity, nano-particle species diffusivity) and micro-organisms (species diffusivity) are considered. Buongiorno’s two-component nanoscale model is deployed and spherical nanoparticles in a dilute nanofluid considered. Using a similarity transformation, the nonlinear systems of partial differential equations is converted into nonlinear ordinary differential equations. These resulting equations are solved numerically using a central space finite difference method in the CodeBlocks Fortran platform. Graphical plots for the distribution of reduced skin friction coefficient, reduced Nusselt number, reduced Sherwood number and the reduced local density of the motile microorganisms as well as the velocity, temperature, nanoparticle volume fraction and the density of motile microorganisms are presented for the influence of wall velocity power-law index (m), viscosity parameter $$({c}_{2})$$ ( c 2 ) , thermal conductivity parameter (c4), nano-particle mass diffusivity (c6), micro-organism species diffusivity (c8), thermophoresis parameter $$(Nt)$$ ( N t ) , Brownian motion parameter $$(Nb)$$ ( N b ) , Lewis number $$(Le)$$ ( L e ) , bioconvection Schmidt number $$(Sc)$$ ( S c ) , bioconvection constant (σ) and bioconvection Péclet number $$(Pe)$$ ( P e ) . Validation of the solutions via comparison related to previous simpler models is included. Further verification of the general model is conducted with the Adomian decomposition method (ADM). Extensive interpretation of the physics is included. Skin friction is elevated with viscosity parameter ($${\mathrm{c}}_{2})$$ c 2 ) whereas it is suppressed with greater Lewis number and thermophoresis parameter. Temperatures are elevated with increasing thermal conductivity parameter ($${\mathrm{c}}_{4})$$ c 4 ) whereas Nusselt numbers are reduced. Nano-particle volume fraction (concentration) is enhanced with increasing nano-particle mass diffusivity parameter ($${c}_{6}$$ c 6 ) whereas it is markedly reduced with greater Lewis number (Le) and Brownian motion parameter (Nb). With increasing stretching/shrinking velocity power-law exponent ($$m),$$ m ) , skin friction is decreased whereas Nusselt number and Sherwood number are both elevated. Motile microorganism density is boosted strongly with increasing micro-organism diffusivity parameter ($${\mathrm{c}}_{8}$$ c 8 ) and Brownian motion parameter (Nb) but reduced considerably with greater bioconvection Schmidt number (Sc) and bioconvection Péclet number (Pe). The simulations find applications in deposition processes in nano-bio-coating manufacturing processes.

Investigation of variable viscosity and thermal conductivity on MHD mass transfer flow problem over a moving non-isothermal vertical plate

In this paper we investigate numerically the influence of variable viscosity and thermal conductivity on MHD convective flow of heat and mass transfer problem over a moving non-isothermal vertical plate. The viscosity of the fluid and thermal conductivity are presumed to be the inverse linear functions of temperature. With the help of similarity substitution, the flow governing equations and boundary conditions are transformed into non-dimensional ordinary differential equations. The boundary value problem so obtained is then solved using MATLAB bvp4c solver. The effects of various parameters viz. magnetic parameter, viscosity parameter, thermal conductivity parameter, stratification parameter and Schmidt number on velocity, temperature and concentration are obtained numerically and presented trough graphs. Also the coefficient of skin-friction, Nusselt number and Sherwood number are computed and displayed in tabular form. The effects of the viscosity parameter and thermal conductivity parameter in particular are prominent. This study has applications in a number of technological processes such as metal and polymer extrusion.

Si-Ge whiskers for thermoelectric sensors design

The paper deals with studies of thermoelectric properties for Si1-xGex (x=0.01-0.05) whiskers doped with boron during their growth by CVD method. Temperature dependences of the resistance and the Seebeck coefficient for Si1-xGex whiskers were measured in the temperature range 275–550 K. A method for determination of thermoelectric parameters of the whisker was proposed with use of the whisker joints, which allows us to define a ratio of Seebeck coefficient to thermal conductivity a/k. Taking into account the obtained values of Seebeck coefficient, the whisker conductance and estimated values of thermal conductivity, parameter ZT was calculated for the whiskers and consists of 0.15 for T=200oC. The obtained value of ZT is in good coincidence with literature data for hop pressed Si-Ge nanocomposites. The humidity sensor was designed base on Si-Ge whiskers.

Thermal Conductivity of the Ga-In System: Experimental Measurements and CALPHAD Modeling

Thermal interface material (TIM) that can exist as liquid at the service temperature enables efficient heat transfer across two adjacent surfaces in electronic applications. In this work, the thermal conductivities of different phase regions in the Ga-In system at various compositions and temperatures are measured for the first time. A modified comparative cut bar technique is used for the measurement of the thermal conductivities of InxGa1-x (x=0, 0.1, 0.214, 0.3, and 0.9) alloys at 40, 60, 80, and 100oC that are the temperatures commonly encountered in consumer electronics. The thermal conductivity values for the liquid and semi-liquid (liquid+β) Ga-In alloys are higher than the TIM currently used in consumer electronics. These measured quantities, along with the available experimental data from the literature, served as input for the thermal conductivity parameter optimization using the CALPHAD (CALculation of PHase Diagram) method for the pure elements, solution phase, and two-phase region. A set of self-consistent parameters for the description of the thermal conductivity of the Ga-In system is obtained. There is good agreement between the measured and calculated thermal conductivity values for all the phases. Hence, it can be envisaged that liquid/semi-liquid Ga-In alloys can be considered as a potential TIM in consumer electronics due to its high thermal conductivity.

Analysis of a Convective-Radiative Continuously Moving Fin with Temperature-Dependent Thermal Conductivity

In this article, the differential transform method (DTM) is used to solve the nonlinear boundary value problems describing heat transfer in continuously moving fins undergoing convective-radiative heat dissipation. The thermal conductivity is variable and temperature dependent. The surface of the moving fin is assumed to be gray with a constant emissivity ɛ. The flow in the surrounding medium provides a constant heat transfer coefficient h over the entire surface of the moving fins. The effects of some physical parameters such as the Peclet number, Pe, thermal conductivity parameter, β, convection-conduction parameter, Nc, radiation-conduction parameter, Nr, and dimensionless convection-radiation sink temperature, θa, on the temperature distribution are illustrated and explained.

Entropy analysis of EMHD non-Newtonian fluid flow induced by Riga plate with slip and convective boundary phenomena

Our paper is consecrated to show the influence of variable fluid properties in EMHD non-Newtonian power-law fluid along a moving Riga plate. Slip velocity phenomenon is considered at the surface which is convectively heated. Entropy analysis is elaborated employing thermodynamic second relation. The governing nonlinear PDEs are altered into ODEs through adequate propinquity transformations which have been solved numerically via the shooting method with the fourth-order Runge–Kutta algorithm through Mathematica software (bvp4c). Characteristics of different basic parameters on velocity, temperature, entropy generation and Bejan number are highlighted through graphs. The outcomes exhibit that the minimum entropy rate in the flow system can be obtained either with rising viscosity parameter and slip parameter or declining dimensionless parameter and thermal conductivity parameter. The entropy rate is minimal for dilatant fluid when compared to pseudo plastic fluid with the most governing parameters. Contrast behavior on the thermal field is noticed for larger values of viscosity parameter and thermal conductivity parameter.