A thermal model for bio-convection transport of nanofluid due to stretching cylinder with Marangoni boundary conditions

The accurate prediction of the SiC MOSFET withstanding time for single fault events greatly influences the requirements for device protection circuits for these devices in power converter applications, like voltage source inverters or power electronic transformers. For this reason, a thermal model, based on the structural design and the physical dimensions of the chip as well as material properties of 4H-SiC, is proposed. This article gives a general description of the thermal behaviour of vertical SiC MOSFET under various driving and boundary conditions in case of a short-circuit event. The thermal model substitutes destructive tests of a device for an individual set of boundary conditions of an occurring fault event. The validity of the analytically parametrised thermal model is verified by experimental short-circuit tests of state-of-the-art vertical SiC MOSFETs for a set of various boundary conditions. The investigated thermal model can furthermore be used to standardise different gate-oxide degradation values from the literature for means of lifetime prediction of the gate oxide for an individual application under repetitive occurring fault or overload conditions. These manufacturer specific reported values measured with no standardised testing procedures can be translated into a maximum junction temperature, which is repeatedly reached. The thermal model therefore provides a unifying parameter for the gate-oxide lifetime calculation for an individual chip and application.

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STEADY MHD MIXED CONVECTION NEWTONIAN FLUID FLOW ALONG A VERTICAL STRETCHING CYLINDER EMBEDDED IN POROUS MEDIUM

International Journal of Engineering Technologies and Management Research ◽

10.29121/ijetmr.v8.i7.2021.990 ◽

2021 ◽

Vol 8 (7) ◽

pp. 45-57

Author(s):

Sharad Sinha ◽

R. S. Yadav

Keyword(s):

Porous Medium ◽

Heat Source ◽

Boundary Conditions ◽

Mixed Convection ◽

Fluid Velocity ◽

Physical Parameters ◽

Stretching Cylinder ◽

Similarity Transformations ◽

Mixed Convective Flow ◽

Source Sink

A viscous electrically conducting fluid is considered and its steady mixed convective flow along a vertical stretching cylinder is investigated. It is assumed that the cylinder is embedded in a porous medium and, external magnetic field, heat source/sink are also taken into account. Suitable similarity transformations are used to reduce the governing equations and associated boundary conditions into a system of nonlinear ordinary differential equations. This system along with the boundary conditions is solved by fourth order Runge-Kutta method with shooting technique. Variations in fluid velocity and temperature due to various physical parameters such as heat source/sink parameter, mixed convection parameter, magnetic parameter are presented through graphs. Effect of these parameters on dimensionless shear stress and rate of heat transfer are discussed numerically through tables.

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Activation energy impact on radiated magneto-Sisko nanofluid flow over a stretching and slipping cylinder: entropy analysis

Multidiscipline Modeling in Materials and Structures ◽

10.1108/mmms-09-2019-0165 ◽

2020 ◽

Vol 16 (5) ◽

pp. 1085-1115

Author(s):

S. Sarkar ◽

R.N. Jana ◽

S. Das

Keyword(s):

Activation Energy ◽

Mass Transfer ◽

Brownian Motion ◽

Boundary Conditions ◽

Entropy Generation ◽

Velocity Slip ◽

Stretching Cylinder ◽

Convective Boundary Conditions ◽

Convective Boundary ◽

Content Type

PurposeThe purpose of this article is to analyze the heat and mass transfer with entropy generation during magnetohydrodynamics (MHD) flow of non-Newtonian Sisko nanofluid over a linearly stretching cylinder under the influence of velocity slip, chemical reaction and thermal radiation. The Brownian motion, thermophoresis and activation energy are assimilated in this nanofluid model. Convective boundary conditions on heat and mass transfer are considered. The physical model may have diverse applications in several areas of technology underlying thermohydrodynamics including supercritical fluid extraction, refrigeration, ink-jet printing and so on.Design/methodology/approachThe dimensional governing equations are nondimensionalized by using appropriate similarity variables. The resulting boundary value problem is converted into initial value problem using the method of superposition and numerically computed by employing well-known fourth-order Runge–Kutta–Fehlberg approach along with shooting technique (RKF4SM). The quantitative impacts of emerging physical parameters on the velocity, temperature, concentration, skin friction coefficient, Nusselt number, Sherwood number, entropy generation rate and Bejan number are presented graphically and in tabular form, and the salient features are comprehensively discussed.FindingsFrom graphical outcomes, it is concluded that the slip parameters greatly influence the flow characteristics. Fluid temperature is elevated with rising radiation parameter and thermal Biot number. Nanoparticle concentration is reported in decreasing form with activation energy parameter. Entropy is found to be an increasing function of magnetic field, Brownian motion and material parameters. The entropy is less generated for shear-thinning fluid compared to shear-thickening as well as Newtonian fluids in the system.Originality/valueTill now no study has been documented to explore the impact of binary chemical reaction with Arrhenius activation energy on entropy generation in an MHD boundary layer flow of non-Newtonian Sisko nanofluid over a linear stretching cylinder with velocity slip and convective boundary conditions.

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Heating Detection and Temperature Control Method of Power Lithium Battery in Pure Electric Vehicle

CONVERTER ◽

10.17762/converter.7 ◽

2021 ◽

pp. 01-08

Author(s):

Guanqiang Ruan Et al.

Keyword(s):

Boundary Conditions ◽

Lithium Ion Battery ◽

Electric Vehicles ◽

Temperature Control ◽

Heat Generation ◽

Thermal Model ◽

Lithium Battery ◽

Lithium Ion ◽

Battery Pack ◽

Electrochemical Characteristics

For the power battery of electric vehicles, especially pure electric vehicles, there is no perfect and comprehensive detection system and management system in the production and use links. By analyzing the working principle, structure and electrochemical characteristics of lithium-ion battery, the heat generation mechanism of lithium-ion battery was studied. In this paper, the factors that affect the temperature characteristics of Li ion battery are described, and the corresponding relationship between the temperature rise of the battery and the ambient temperature is established. At the same time, the optimal temperature range of the battery pack discharge efficiency is determined. In this paper, the thermal effect model and heat generation rate model of lithium-ion battery are established, and then the thermal conductivity, specific heat capacity, density and other parameters of the thermal model are calculated. Finally, the initial and boundary conditions of the thermal model are determined, the simulation of heat generation temperature field is realized, and the temperature distribution of the battery after heat generation is obtained. In this paper, the flow mode of air is analyzed, and the fluid structure coupling model of battery air is established. Finally, the thermal field of the battery pack is simulated by setting the solver mode and boundary conditions, which makes a theoretical analysis for the preliminary design of the temperature control battery box. The test results show that the method proposed in this paper can meet the technical requirements of power lithium battery heating management of pure electric vehicles..

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