Convective Conditions Research Articles

Indirect thermographic die temperature measurement of a SiC-based semiconductor diode under the conditions of natural and forced convection

ABSTRACT Information about the die temperature of a semiconductor diode is important to the designer. The shape of the current-voltage characteristics of the semiconductor diode and its operating parameters depend on the value of this temperature. Semiconductor devices that conduct a high current can reach high die and case temperatures. This temperature can be determined by thermographic temperature measurement. The temperature value of the semiconductor diode case will depend on the conditions under which it is operated. For many semiconductor devices, the temperature difference between the case and the die will depend on the convection. Research work was carried out to determine the difference between the die temperature of the semiconductor diode made on the basis of SiC FFSH10120A and its case. The method of making a thermographic temperature measurement of the case of a semiconductor element has been presented and the place where this measurement should be made has been indicated. It was found that in the case of natural convection, the largest difference between the temperature of the semiconductor element and the temperature of its case was 40.1 K. For forced convection, the largest difference between these temperatures was 33.1 K for v = 0.75 m/s and 23.9 K for v = 1.5 m/s.

On the Efficiency of Air-Cooled Metal Foam Heat Exchangers

This study analyses the heat transfer performance of metal foam heat exchangers through experimental measurements. Using counter-gravity infiltration casting, open-cell aluminium foam elements were manufactured to embed a copper tube for internal mass flow containment. Heat transfer experiments were conducted under natural and forced convection conditions, with the airflow controlled in a wind tunnel. A stream of warm water within the internal foam component served as the heat source, transferring thermal energy to the surrounding air flowing through the external foam component of the heat exchanger. The results showed a significantly enhanced heat transfer performance with aluminium foam compared to a single copper tube. Thermal resistance models were developed to elucidate the heat transfer mechanisms, highlighting the effectiveness of air-cooled metal foam heat exchangers. These findings underscore the potential of metal foam heat exchangers as cost-effective alternatives for various thermal management applications.

Application of central composite design (CCD)-response surface methodology (RSM) for optimization of heat transfer in dusty nanofluid flow with velocity slip

Background and Purpose The consequence of thermal radiation is scrutinized on the heat transport of Nano-diamond/silicon oil and silver/silicon oil nanofluids through a stretching endless plate. The single phase (Tiwari and Das) model is employed for nanofluid. The major objective of this study is to optimize the RSM-based Central composite design modeling to optimization of the heat transfer in dusty Oldroyd-B nanofluid across stretching surface. Additionally the velocity slip effect is considered. The dust particle phase is also taken into account. The significance of viscous dissipation, joule heating, inclined magnetic field with convective condition is investigated. Methodology The partial differential equations are developed under consideration, then transform to ODE’s by utilizing similarity tools. The transformed model of ODE’s is tackled numerically via bvp4c MATLAB tool with shooting algorithm. The effect of magnetic parameter, fluid interaction parameter, nanoparticle volume fraction, slip parameter and temperature interaction parameter on velocity field and temperature distribution of fluid phase and dust phase is investigated. Furthermore the Nusselt number on the wall is observed for interactive parameters of mass concentration of dust particles, fluid particles interaction parameter for velocity and unsteady parameters utilizing the face-centered Central Composite design (CCD) of the Response Surface Methodology (RSM). Additionally, Analysis of Variance (ANOVA) algorithm and 3D plots are utilized to examine the consequence of experimental design parameters via the response. The recommended model significance has been analyzed in conditions of correlation coefficient ( R 2 ), mean square error (MSE), root means square error (RMSE), prediction standard error to acknowledge the most excellent strong. Results The difference between the Predicted R2 of 0.9467 and the Adjusted R2 of 0.9867 is less than 0.2, which is assumed to be a reasonable concurrence. Furthermore results of the current analysis indicate that velocity gradient for nanofluid is diminishes for larger fluid particle interaction parameter for velocity, while the dust phase velocity is improved. The increment in Temperature gradients is observed via increasing values of the nanoparticle fraction and temperature base fluid particle interaction parameter. From the results it is concluded that skin friction coefficient is reduced with larger magnetic parameter for both mono nanofluids. Furthermore the heat transfer rate is increased by increasing the thermal radiation parameter for both mono nanofluids. It is concluded that silver/silicon oil nanofluid play a higher role in heat transportation as compare to Nano-diamond/silicon oil.

Investigation of momentum and heat transfer characteristics of Maxwell fluid cascading over a stretching sheet: A HAM approach

This paper presents a novel investigation into the intricate behaviour of momentum and heat transport phenomena in a non-Newtonian Maxwell fluid flowing over a stretching sheet. Incorporating thermal radiation Rd, magnetic fields M, buoyancy effects λT, and porous media K under convective boundary conditions the study unveils complex fluid behaviours. Energy equation has been obtained by incorporating non-uniform heat source/sink along with viscosity of the fluid as a function of temperature across the domain. Leveraging the Lie Scale transformation technique, the governing non-linear partial differential equations are converted into non-linear ordinary differential equations. With the aid of Homotopy Analysis Method (HAM), a semi-analytical technique, the solutions describing the physical phenomenon of the current model have been obtained. Further, the results are assessed through the graphical analysis of the velocity profile f′η, thermal profile θη, skin friction coefficient CfRe12, and Nusselt number NuRe−12. The obtained results using HAM shows good agreement with the existing literature. The present work offers practical implications for various engineering applications.

Local thermal resistance delamination method for precise analysis and optimization of heat transfer processes

Excessive carbon emissions are one of the global challenges. Promoting the optimization of high-efficiency heat transfer systems and improving the analysis and evaluation methods of heat exchangers is one of the effective ways to save energy and reduce carbon emissions. The traditional thermal resistance analysis method treats the fluid domain as a uniform whole, which makes it difficult to regulate the heat transfer characteristics in local regions, especially in the near-wall region. To address this problem, this paper obtained the thermal resistance mathematical equation for different regions in the flow field by magnitude analysis. The thermal resistance delamination method for dividing the thermal resistance field is proposed from the channel flow, and the conduction, mixing and advection zones in the flow field are identified. The delamination factor (α) is defined to determine the boundaries of thermal resistance zones. The α values which meet the delamination factor independence under forced convection and natural convection conditions are investigated. By studying the mechanism of the thermal resistance in conduction zone of the enhanced heat transfer structure, the critical value of fin height to achieve maximum enhancement efficiency is determined. The thermal resistance delamination facilitates a comprehensive analysis of heat transfer processes and structure optimization in the near-wall region.

Heat and mass transmission through the nanofluids flow subject to exponential heat source/sink and thermal convective condition across Riga plates

The analysis of the squeezing nanofluid flow across bounded domains received great attention from researchers and engineers due to its tremendous application in automobiles, energy exchangers, and aerodynamics. In the current analysis, we are using double Riga plates parallel to each other, in order to induce the squeezing nanofluids flow with the significances of chemical reaction, thermal radiation, and heat source/sink. The nanoliquid has been prepared by the dispersion of Copper (Cu) nanoparticles (NPs) in kerosene oil (C12H26C15H32) and water (H2O). The nanofluid flow has been modeled in form of nonlinear partial differential equations, which are further convert into the dimensionless form of ordinary differential equations. The obtained set of non-dimensional equations is numerically resolved by using the Matlab built-in package bvp4c. The results are compared to another numerical technique for accuracy purposes. The detailed results are presented in Figures. It has been detected that the energy field of nanofluid is enriched with the effect of heat source/sink component. Moreover, the velocity curve magnifies with the variation of the squeezing parameter of Riga plates, whereas declines with the accumulation of Cu-NPs in both types of base fluid (C12H26C15H32 and H2O).

MHD nanofluid flow and heat transfer caused by a stretching sheet that is heated convectively: An approximate solution using ADM

The investigation detailed in this paper explores the behavior of a slippery nanofluid flowing over a permeable stretched sheet under the influence of magnetohydrodynamic forces, considering factors like thermal radiation, viscous dissipation, and convective boundary conditions. The analysis systematically establishes principles for conserving mass, heat, momentum, and nanoparticle concentration, deriving a set of nonlinear ordinary differential equations from the governing partial differential equations. To tackle these challenges, the Adomian decomposition approach is utilized as a central element of the solution methodology. Graphical representations are employed to depict the solutions across various physical parameters. Despite the significance of nanofluids in both industrial and scientific contexts, there exists a noticeable research gap concerning the combined impacts of thermal radiation, viscous dissipation, and convective boundary conditions on heat and mass transfer, especially when coupled with a permeable linear rough stretched sheet. This study aims to fill this void by offering quantitative insights into these intricate phenomena, thereby enhancing our understanding of nanofluid dynamics and their practical implications. The findings indicate that increasing slip velocity and magnetic parameters reduce the boundary layer thickness of the velocity profile but increase it for the temperature profile, suggesting a nuanced interplay between slip velocity and magnetic effects on velocity boundary layers, while the temperature boundary layer exhibits distinct thermal dynamics within the system.

Comparative analysis of viscous dissipation effects on Prandtl fluid including contraction and relaxation phenomena

AbstractThis paper investigates the effects of magnetohydrodynamics and heat transfer on the peristaltic transport of Prandtl fluid in a vertical endoscopic tube. The reduction of the complexity of the equations governing the flow of Prandtl fluid entails the use of long wavelength and low Reynolds number approximations. These complex equations for the pressure gradient and velocity profile are handled analytically using the perturbation technique with convective boundary conditions, and the temperature and concentration profiles are carefully solved for the exact solution. The frictional forces and pressure rise are also simulated with numerical integration. The resulting formulas for velocity, temperature, concentration, pressure rise, and pressure gradient are graphed using the MATLAB and MATHMATICA software, and the effects of all the different physical parameters are investigated and assessed. The streamlines with five distinct wave types are sketched at the conclusion to show the phenomenon of trapping. It is investigated that the velocity profile rises due to buoyancy forces and falls due to the influence of magnetic forces.

Numerical simulation and experimental study on effect of cooling rate on microstructure and strength of nanostructured materials

In this study, by numerical simulation (finite element method, FEM) and experimental, the cooling rate was investigated by changing the product thickness (20, 3, 2, 1, 0.5 and 0.3) mm of Al based two-phase nanostructured materials casted through a copper mold. The effect of cooling rate on the microstructure and strength of the alloy was studied. The Experimental results showed that the precipitated intermetallic phases have a decreasing size corresponding to the increasing cooling rates by simulation from ~102 K/s to ~104 K/s. The results show that an appropriate cooling rate can improve the microstructure and properties of the alloy. The Abaqus/Standard capability for uncoupled heat transfer analysis was intended to model solid body heat conduction with general, temperature-dependent conductivity; internal energy (including latent heat effects); and quite general convection and radiation boundary conditions. This study describes the basic energy balance, constitutive models, boundary conditions, finite element discretization, and time integration procedures used. The time step used an automatic algorithm through the smallest tolerance. The maximum temperature change was allowed over a period and the increment was adjusted for this parameter, as was the rate of convergence in the non-linear cases. First-order heat transfer elements used the rule of numerical integration with integrated stations located at the corners of the element for thermal capacitance terms. (Jacobian terminology). This approach is particularly effective when there is a strong latent thermal effect. Thus, first - order elements were used in the case of latent heat. The HEATCAP element is available for single - point pooled thermal capacitance modeling. Centralized film loading options between the mold and the casting were specified by the user.

Viscous fluid flow and heat transfer past a permeable wall jet with convective boundary conditions

PurposeThe steady laminar wall jet flow over a stretching/shrinking surface in the presence of lateral suction or injection with a convective boundary condition is considered.Design/methodology/approachThe partial differential equations for mass, momentum and energy conservation are changed to the system of ordinary differential equations through similarity solution transformations. Solutions, both numerical and asymptotic, to these similarity equations are found in some new ranges of parameters in the governing equations.FindingsThe equations are solved both asymptotically and numerically for a range of the transpiration parameter S and the flow parameter λ given in Mahros et al. (2023), thus greatly extending the range of these previous solutions. Asymptotic solutions for both large and small values of the Prandtl number σ are derived, showing good agreement with additional numerical integrations. It should be noted that in Mahros et al. (2023), only the case when σ=1 was treated. A solution for large λ when S=1 is obtained, showing a different asymptotic form to the case when S>0 in Mahros et al. (2023). Multiple solutions were seen by them for S<0 and the nature of the lower solution branch as S→0 from below is discussed. The question as to whether the lower branch solutions join as λ>0 when S<0 is resolved through obtaining an asymptotic solution λ small.Originality/valueThe accuracy of the solutions has been checked through a detailed comparison between the solutions obtained numerically and analytically, where excellent agreement has been found. This study is important for scientists working in the area of jet flows to become familiar with the flow properties and behaviour of jets.

Entropy generation on inclined magnetize double diffusive convective transportation of radiative Casson nanofluid in porous medium with source/sink

This research intends to investigate the entropy generation on the magnetized double diffusive heat and mass transfer flow of the Casson nanofluid under the influence of an inclined magnetic field in a porous medium. Additionally, the combined impact of heat absorption, chemical reaction, Brownian diffusion, source/sink, and thermophoresis phenomena is also taken care of. The fluid flow involves convective boundary conditions for both temperature and concentration instead of a constant value at the surface. The flow-regulating system involved nonlinear PDEs that are turned into nonlinear systems of ODEs by using scaling variables and then solved this system numerically in Matlab using the bvp4c strategy, which is a collocation technique based on the Lobatto 3-stage FDM algorithm. Graphical representations illustrate the behavior of fluid velocity, entropy generation, concentration, and temperature in response to changes in flow parameters. Physical quantities like skin friction coefficient, Nusselt number, and Sherwood number have been investigated using 2D and 3D plots. Here, we concluded that the inclined magnetic field decimates the flow velocity gradually and greater values of the magnetic field lead to an increased rate of entropy generation. Furthermore, it has been noted that the temperature profile improves as the Brownian motion of particles increases, and the distribution of energy also enhances with larger values of the thermophoresis. The obtained key findings are discussed in a physical manner using graphic representation.

Thermal behavior (in cooling) of soil mass with varying fine and water contents: Experimental and numerical investigation

This paper presents a preliminary study on the thermal behavior and response of soil samples with varying water content to assess their significance in addressing the nighttime urban heat island (UHI) effect. For this reason, the experimental program and the analysis focus on the cooling phase of the heated soil samples. To ensure a representative analysis of field conditions, the soil samples were prepared in the laboratory with varying coarse-grained (sand) and fine-grained (kaolin) soil particles. The thermal properties of the soil samples, including thermal conductivity and transmissivity, decrease with increasing fine content and particle packing. In contrast, the thermal conductivity and transmissivity values increase with water content. The thermal diffusivity followed a similar behavior but was relatively less prominent. On the other hand, the specific heat capacity is higher in samples with higher moisture and clay contents but lower with dry unit weight. However, having a higher specific heat capacity also resulted in samples retaining the heat relatively longer and releasing it slowly, which could contribute to delayed nighttime UHI. The numerical models considering natural convective conditions and their analysis further confirm that the water content of the soil samples has a relatively more prominent effect on the soil’s specific heat capacity than the increasing clay contents. To this end, it is noted that the measurement, analysis, and estimation of heat transfer and cooling mechanisms in the soil requires careful consideration of the soil type, water content, and the surrounding environmental conditions.

Numerical analysis of magnetohydrodynamic free stream and radiative heat transfer flow of nanofluid in a permeable medium over a linearly stretched cylinder with Arrhenius activation energy

This research article explores the transport characteristics of magnetohydrodynamic Newtonian nanofluid flowing past a stretching cylinder in a permeable medium, considering the activation energy effects using Buongiornos mathematical model. Unlike conventional studies employing constant temperature, concentration and density boundary conditions, convective boundary conditions are utilized in this investigation. The analysis incorporates various significant parameters such as magnetic field, joule heating, viscous dissipation, thermophoresis, Brownian motion, Arrhenius activation energy, and chemical reaction. The governing equations in the form of ODEs are obtained by employing similarity variables.The MATLAB built-in solver bvp4c is employed for obtaining the solutions. The impacts of these parameters on the velocity profile, temperature profile, concentration profile, density profile, skin friction coefficient, Sherwood number, and Nusselt number are elucidated through graphical and tabular representations. The results indicate that an increase in the chemical reaction parameter leads to higher nanoparticle concentration distributions, while the activation energy parameter exhibits the opposite trend. This study holds relevance for various practical applications in applied sciences, including nuclear reactor cooling, geothermal reservoirs, chemical engineering, and thermal oil recovery.

Generalized aspects of Fourier’s and Fick’s laws through Cattaneo–Christov model on nanofluid flow with multiple convective conditions and chemical reaction: a statistical approach

Generalized aspects of Fourier’s and Fick’s laws through Cattaneo–Christov model on nanofluid flow with multiple convective conditions and chemical reaction: a statistical approach

Numerical simulation of Buongiorno's model on Maxwell nanofluid with heat and mass transfer using Arrhenius energy: a thermal engineering implementation

The thermal features of nanoparticles owing to progressive mechanisms are a fascinating phenomenon due to their applications in energy production, cooling procedures, heat transmission devices. Therefore, in the present study, the magnetohydrodynamic combined convection of Maxwell nanofluid and characteristics of heat transport in the presence of thermal radiation with a nonlinear relationship for modifications in the energy equation have been examined. Moreover, the features of activation energy in the presence of swimming microorganisms are considered. For motivation, the influence of bioconvection, magnetic field, and thermophoresis with convective boundary conditions are part of this investigation. The governing PDEs connected with momentum, energy, concentration, and density are converted into ODEs by using similarity functions. A transformed, dimensionless, nonlinear set of ODEs is tracked via a shooting scheme. The numerical results of prominent parameters have been analyzed in the form of graphs and tables using the computational software MATLAB. A significance improvement in the velocity profile is noted for the increasing value of Maxwell parameter. With rise of mixed convection parameter, both energy and volumetric friction field deteriorated. The determination of Biot number that is associated with the coefficient of heat transfer is more effective for growing the temperature and volumetric friction distribution. These conclusions may be appreciated in improving the efficiency of heat transfer strategies.

Numerical Study of Natural Convective Flow of a Nanofluid Over Rotating Truncated Cone with Convective Heating

In this paper, we consider the natural convection flow of a nanofluid simultaneously heat and mass transfer over a truncated rotating porous cone with convective boundary condition. Buongiorno’s model is used to describe the present nanofluid flow problem which is represented by Brownian motion and thermophoresis effects. Governing set of nonlinear boundary layer equations for the nanofluid over a rotating truncated cone is converted into a set of non-similar forms through non-similarity transformations. The obtained reduced nonlinear PDE system is linearized locally and solved via an accurate Chebyshev Spectral Collocation Method. The accuracy of the obtained numerical solutions is tested against existing results in the literature for specific cases and demonstrates good agreement. In addition, the impacts of active parameters such as the rotational parameter (0 ≤ χ ≤ 3), Biot number (0.1 ≤ Bi ≤ 1), and suction/injection parameter (−0.5 ≤ fw ≤ 0.5) on velocities, temperature, and nanoparticle volume fraction profiles along with heat and mass transfer rates are examined. It is found that the local surface drag and heat transfer rate increase, and the nanoparticle mass transfer rate decreases, with the increase in both the spinning parameter and Biot number.

Comparative Study of Convective Oldroyd-B Nanofluid and Hybrid Nanofluid Flow, Heat and Mass Transfer Analysis Over Stretching Sheet with Cattaneo-Christov Heat Flux Model

The current analysis appraises the flow, heat and mass transfer characteristics of Oldroyd-B nanofluids SWCNT-Water and hybrid nanofluids SWCNT/MWCNT-Water over the stretching sheet. Thermal radiation, modified Fourier heat flux and convective boundary conditions are also used to evaluate the flow. Graphs are used to compare the characteristics of nanofluid SWCNT-Water and hybrid nanofluid SWCNT/MWCNT-Water nanofluids in terms of concentration, temperature, and velocity. The flow mechanism is modelled in the form of nonlinear system of partial differential equation. These PDEs are converted into Ordinary differential equations by using the similarity variable techniques. The Finite Element Method is pre-owned to solve the obtained ODEs. Plots are used to show the results of temperature, concentration and velocity for both nanofluids for various values of the relevant parameters. The dimensionless skin friction coefficient, Nusselt number and Sherwood number values are scrutinized and revealed in tabular form. The important findings of this study reveal that the scattering of temperature and concentration of both SWCNT-Water nanofluid and SWCNT/MWCNT-Water hybrid OBF nanofluid elevates with amplifying values of thermal retardation parameter. With increasing values of the power low index number the sketches of temperature and velocity are both attenuate in the fluid region.

Experimental and numerical analysis of a liquid-air hybrid system for advanced battery thermal management

This study introduces an innovative hybrid Battery Thermal Management System (BTMS) that combines air and liquid cooling mechanisms for optimal thermal control in small-scale EV applications. Recognizing the limitations of the existing single-method cooling systems, we developed a novel Hybrid Battery Thermal Management System that combines air and liquid cooling to provide superior temperature management. Additionally, we performed a detailed experimental evaluation to verify the accuracy of our heat generation model for lithium-ion batteries. This included the construction and testing of the proposed hybrid cooling system in a controlled environment using a climate chamber that simulated various ambient temperatures. We assessed the system performance under different operational stresses, specifically at 1C and 2C discharge rates. The tests encompassed a range of temperatures, starting at a standard room temperature (20 °C) and increasing through three levels of ambient temperature: 30, 35, and 40 °C. Initial tests under natural convection conditions showed a non-uniform temperature distribution and temperatures near the upper safety limits, with a maximum of 51 °C. While the addition of an air-cooling system provided some improvement, it still resulted in localized hotspots. However, the hybrid battery thermal management system effectively addressed these challenges, achieving marked improvements in cooling efficiency and temperature uniformity, yielding a 21.04 % improvement in cooling by reducing the maximum temperature at 2C from 51.2 °C (no cooling) to 40.9 °C while also improving the uniformity of the temperature distribution among the packs. Further tests at elevated ambient temperatures confirmed the robustness and adaptability of this system. These findings highlight the scalability of the system and suggest its potential applicability to larger battery systems, opening avenues for future research and practical implementation.

A numerical investigation of the magnetized water-based hybrid nanofluid flow over an extending sheet with a convective condition: Active and passive controls of nanoparticles

Abstract This study presents a numerical investigation of a viscous and incompressible three-dimensional flow of hybrid nanofluid composed of Ag and Al2O3 nanoparticles over a convectively heated bi-directional extending sheet with a porous medium. The main equations are converted into dimensionless form by using appropriate variables. The effects of magnetic field, porosity, Brownian motion, thermophoresis, and chemical reaction are investigated. Furthermore, the mass flux and zero-mass flux constraints are used to study heat and mass transfer rates. The obtained data show that the growing magnetic factor has reduced the velocity profiles while increasing the thermal profile. The increased porosity factor has decreased the velocity profiles. The increased thermal Biot number has increased the concentration and thermal profiles. When compared to passive control of nanoparticles, the hybrid nanofluid flow profiles are strongly influenced by the embedded factor in the active control of nanoparticles.

Numerical analysis of the flow dynamics in Maxwell hybrid nanofluid flow with gyrotactic microorganisms over a permeable stretching surface with convective and zero-mass flux conditions: A comparative analysis

This study observes the 2-D flow of a Maxwell hybrid nanofluid flow on a permeable stretching surface containing Cu and CuO nanoparticles and gyrotactic microorganisms. The thermal convective and zero-mass flux constraints are adopted by incorporating a hot working fluid with a heat transfer coefficient and zero mass flow at the permeable sheet’s surface to investigate the heat transfer rate. This study is designed to present a comparative analysis of the nanofluid (Cu–water) as well as hybrid nanofluid (Cu–CuO/water) flows on a stretching sheet. Examining activation energy in water-based hybrid nanofluid flow offers important insights into the kinetics of chemical reactions, which in turn helps to optimize the features of the nanofluid and build more effective systems that use nanofluids for a variety of applications. The problem formulated initially is converted to dimension-free notation using appropriate variables for finding the numerical solution by incorporating the bvp4c MATLAB function. From the obtained results, it is found that the higher magnetic and porosity factors have declined the velocity profiles. Also, in the absence of porous media and magnetic field effects, the velocity distribution is highly affected when compared with the existence of these effects. It is observed that the velocity profiles of both nanofluids are dominant for Newtonian fluid in comparison to non-Newtonian fluid. Also, the thermal profiles of both nanofluids are dominant for non-Newtonian fluid in comparison to Newtonian fluid. The friction force of hybrid nanofluid is significantly influenced by the magnetic factor, porosity factor, and volume fractions of the solid nanoparticles when compared to nanofluid.