Search

In this paper, electrothermal modeling and simulation of thermoelectric cooling (TEC) in the package design of VLSI systems are performed by solving coupled heat conduction and current continuity equations. We propose a new analytical solution to the coupled partial differential equations which describe temperature and voltage with the reduction from 3D to 1D. In addition to this, we derive new analytic expressions for two key performance metrics for TEC devices: the maximum temperature difference and the maximum heat-flux pumping capability, which can be guided for the optimal design of thermoelectric cooler to achieve the maximum cooling performance. Further, for the first time, we observe that when the dimensionless figure of merit ZT0 value is larger than 1, there is no maximum heat-flux value, which means the heat dissipation due to Peltier and Fourier transfer effects is larger than the heat generation caused by Joule heating effect, which can lead to more efficient TEC cooling design. The accuracy of the proposed 1D formulas is verified by 3D finite element method using COMSOL software. The compact model delivers many orders of magnitude speedup and memory saving compared to COMSOL with marginal accuracy loss. Compared with the conventional simplified 1D energy equilibrium model, the proposed analytical coupled multiphysics model is more robust and accurate.

In recent years, utilization of nano-technology in drugs and cancer growth treatment has produced a great deal of temptation in thermal properties of biological nanofluid, for example, blood with nanoparticles suspension. The objective of this research is to discover a MHD naturally bio-convective flow of non-Newtonian bio-nano-fluid containing blood as base fluid with ( A l 2 O 3 ) alumina nanoparticles suspension carrying effect of buoyancy, chemical reaction, moving microorganism and heat generation near stagnation region. The Buongiorno along Tiwari and Das nanofluid model is employed whereas Oldroyd-B model is capitalized for depicting the viscoelastic behavior of blood. The non-similarity transformations are exercised on governing nonlinear partial differential system (PDE’s) to transform them into system of non-dimensional PDE’s. After applying appropriate transformations the local non-similarity method via bvp4c algorithm is adopted to numerically deal with the problem. The significance of parameters such as Grashof numbers, magnetic field, Brownian motion, thermophoresis, Deborah numbers, Prandtl number, Schmidt number, Peclet number, heat generation/absorption number and chemical reaction on velocity, temperature, concentration and density of moving microorganism are computed in the graphical profiles to explain the physical state of problem. Physical quantities i.e. local Nusselt number, local Sherwood number and local microorganism density number are also calculated.

As the demand for lithium-ion batteries increases, a better understanding of the complex phenomena involved in their operation becomes crucial. In this work, we propose a coupled thermo-chemo-mechanical model for electrode particles of Li-ion batteries. To this end, we start with a general finite strain continuum framework for the coupled thermo-chemo-mechanical problem and then narrow it down to cathode active particles of Li-ion batteries, particularly to lithium manganese oxide particles. Electrochemical kinetics at the surface of the particle and also heat generation due to current exchange are taken into account. Next, the numerical treatment of the problem using the finite element method is presented. Specific line elements are needed to evaluate the flux of ions at the surface of the particle. Finally, the performance of the proposed model is evaluated using a few representative boundary value problems., Deutsche Forschungsgemeinschaft, Projekt DEAL

Convection differential equations that include momentum, energy and mass balance equations are used for the simulations of boundary layer (BL) flows. In convection analysis, it is in execution to dimensionless the BL system through similarity variable. However, a wide range of convection differential equations cannot be non-dimensionalized using similarity variable therefore the intent of this manuscript is to develop non-similar model for the forced convective magnetic flow of a viscous fluid above an exponentially expanding surface saturated by nano-fluid. The non-similarity is due to the exponential stretching of the surface and viscous dissipation. Influences of chemical reaction and heat generation are also incorporated. The non-similarity transformation is applied to the nonlinear partial differential system (PDE’s) to transform them into dimensionless PDE’s. Non-similar system is analytically approximated by adapting local non-similarity (LNS) and then it is numerically simulated by finite difference based bvp4c algorithm to explore the influences of significant numbers named as Prandlt number, chemical reaction, magnetic field, Brownian motion, heat generation, Eckert number, thermophoresis on concentration, velocity and temperature distribution. Auxiliary consequences presume that the heat penetration in fluid rises with enhancements in Brownian motion and Prandtl number, while it can be perceived here that for positive estimations of heat generation causes the thicker temperature field. Increasing non-similarity variable and magnetic number become reason for the reduction of temperature profile and chemical reaction is reason of reduced concentration profile.

Partial filling of a porous medium in a channel of a certain configuration attracts attention, as it tends to enhance convective heat transfer while reducing pressure drop remarkably, as compared t...

Li-ion battery packs provide high energy density but with a concern of thermal management. Hence cooling mechanism is necessary to have a good life and reliability on the battery system. The main objective of this article is to investigate the effect of conjugate and non-conjugate boundary conditions on battery pack heat transfer characteristics. In conjugate conditions, coolant flow is considered with heat flux continuity at the battery and fluid interface. In non-conjugate condition, just convection condition is adopted. The finite volume method is adopted for the numerical analysis, and a code is written for computations of the governing equations. Effects of different parameters like heat generation, conductivity ratio, coolants, and Biot number on temperature distribution in the battery pack are analyzed. The maximum temperature contours are located near the top end of the battery, whereas at the bottom end, the battery's temperature is low. Such high and low-temperature regions in the battery pack create uneven thermal stresses, resulting in battery failure. To have better performance results for the battery system, one should maintain the proper balance of thermal conductivity between the solid and fluid domains. From comparative analysis it is found that the non-conjugate condition gives the temperature distribution in battery to be of symmetrical nature and more uniform. Practically, this is not true which is confirmed by the realistic conjugate condition where the high temperature zones are closer to the trailing edge of the battery pack. Liquid metals and nanofluids provide a much safer operating temperature of the pack where the maximum temperature is well below the critical temperature. The application of conjugate condition for battery thermal analysis leads to be have an insight of the hotspot zones accurately which are operated using conventional fluids mentioned in this work.

Thermal diffusion and wave phenomena in a two-dimensional solid subjected to convective cooling and an internal exponential heat source are investigated. Both diffusion and Cattaneo–Vernotte (C–V) ...

Large battery packs are used in electric vehicles. Heat is generated when the battery pack is being used. Therefore, it is necessary to predict battery heat generation. An enhanced electro-thermal model is developed to describe the temperature distribution inside a battery pack. It combines the dynamic resistance model and the current distribution model. The resistance model is affected by the thermal and electrical parameters, while the current distribution model considers the interaction between cell status and current variation in the parallel branch. The proposed model can accurately predict the temperature change of cells in the pack under static and dynamic current conditions. Experiments are conducted to validate the prediction accuracy. Most of the average absolute errors (AEave) between the predicted value and test value displayed on the experimental device do not exceed 0.4 °C under static current conditions, and all of them are below 0.1 °C under dynamic current conditions. The two existing models, namely the state-of-charge (SOC)-dependent resistance model [R(SOC)] and SOC-T-dependent resistance model [R(SOC, T)], have AEave values of 1.6 and 0.54 °C when the pack is discharged at 0.5 C. In contrast, the AEave value achieved by our proposed model is 0.4 °C. Under dynamic current conditions, the maximum AEave s are 0.42 °C for the R(SOC) model, 0.26 °C for the R(SOC, T) model, and 0.16 °C for the proposed model. These results demonstrate that the proposed model provides more accurate predictions of the temperature rise inside the pack than the popular existing models.

Heat dissipation is becoming more and more challenging with the preface of new electronic components having staggering heat generation levels. Present day solutions should have optimized outcomes with reference to the heat sink scenarios. The experimental and theoretical results for plate type heat sink based on mathematical models have been presented in the first part of the paper. Then the parametric optimization (topology optimization) of plate type heat sink using Levenberg-Marquardt technique employed in the COMSOL Multiphysics® software is discussed. Thermal resistance of heat sink is taken as objective function against the variable length in a predefined range. Single as well as multi-parametric optimization of plate type heat sink is reported in the context of pressure drop and air velocity (Reynolds number) inside the tunnel. The results reported are compared with the numerical modeled data and experimental investigation to establish the conformity of results for applied usage. Mutual reimbursements of greater heat dissipation with minimum flow rates are confidently achievable through balanced, heat sink geometry as evident by the presented simulation outcome. About 12% enhancement in pressure drop and up to 51% improvement in thermal resistance is reported for the optimized plate fin heat sink as per data manifested.

In this manuscript a study of the unsteady magneto-hydrodynamic mixed convection Jeffrey fluid flow over an inclined permeable moving plate in presence of thermal radiation, heat generation, radiation, aligned magnetic field, thermophoresis effect and homogenous chemical reaction, subjected to variable suction has been undertaken. The governing equations are solved by using a regular perturbation technique. The expressions for the distributions of velocity, temperature and species concentration are obtained. With the aid of these, the expressions for skin friction, Nusselt number and Sherwood number also have been derived. The influences of various physical Parameters involved in the problem on the above mentioned quantities are discussed with the help of graphs and tables. From the significant findings, it has been found that the velocity increases with an increase in Jeffrey fluid in the presence of permeability. It shows reverse effects in the case of magnetic parameter, radiation parameter and chemical reaction parameter. Comparisons with previously published work performed and the results are found to be in the excellent agreement.

Internal-cooling method due to its numerous advantages has been used during the machining of hard to cut and difficult to machine materials. Cooling channels developed in the cutting inserts, drills, end mills and grinding wheels are used for the heat removal which is concentrated at a smaller region during machining process. So, these cooling channels play a vital role in decreasing the temperature and wear rate of the tools. The heat generation and transfer rate depend upon the physical configuration of the cooling channel. This research work presents novelty in the concept of developing internal cooling channel cutting inserts with different profiles. Three different profiles have been developed to investigate cooling effect on the turning tool insert with different shapes. The results have been compared with the standard tool having no cooling channel. Computational Fluid Dynamics (CFD) has been used to simulate temperature rise for all profiles. A temperature drop of 188 K has been found for internally cooled cutting insert in comparison to the standard tool having no channel. It has also been found that the temperature difference of range 20 K–88 K can be achieved by varying the profile of the channel. Besides this, an increase in the inlet pressure of the cutting fluid has been found to make the coolant profile more efficient in terms of heat removal. Through the velocity vector results, it has been found that with more flow velocity of coolant inside the channel more heat transfer takes place. Turbulence Kinetic Energy (TKE) results showed that the heat transfer rate can be increased with an increase in the TKE value which in turn depends upon the profile of the coolant flow channel. This CFD study in turn has laid the platform for setting the optimum parameters during the turning of Titanium alloy with internal cooling channels.

In order to investigated the influence on the liquid cooling system cooling effect by changing the structural parameters, single Li-ion battery heat generation model is conducted, and used in following simulation. Subsequently, sixteen models are designed by orthogonal array, and the results are obtained by extremum difference analysis, which can quantify the influence degree, identify major and minor factors, and find the relatively optimum combination. Finally, different channel entrance layout is adopted to investigated. With a series of work, the effective of single battery heat generation model is proved by the discharge experiment. The coolant velocity has most evident influence on the Li-ion battery temperature rise, rectangular channel aspect ratio is second one, and the heat conducting plate thickness has the smallest influence. Similarly, for Li-ion battery temperature difference, the effect of heat conducting plate thickness and rectangular channel aspect ratio as the same, both are secondary factor, and coolant velocity is main factor. With different channel entrance layout, both the maximum temperatures denote a same upward trend, and better balance temperature distribution is obtained by adopt Case C system which with alternating arrange channel entrance layout.

In this paper, the effect of viscous dissipation and Joule heating on magneto-hydrodynamic (MHD) nanofluid flow towards a vertical sinusoidal wavy surface has been investigated numerically. The wavy surface is considered to be heated with uniform flux. Effects of radiation and nanoparticle volume concentration are also considered. The fluid flow over the surface geometry is designed through the highly non-linear partial differential equations, and governing equations must be transformed into a dimensionless non-similar system of equations to get a better solution by applying the highly efficient well-known Keller-box scheme. In this regard, the numerical solutions are obtained for a concentration of mass fluid, velocity profile, temperature profile, local skin friction number coefficient, local Nusselt number, and Sherwood number shown graphically. Connected parameters involve in the modelled problem such as heat generation parameter, radiative conduction flow parameter, the amplitude of the waviness of the surface, Prandtl number, Brownian motion parameter, Buoyancy ratio, magnetic parameter, Thermophoresis parameter and the Lewis number for momentum, temperature profile, and concentration profile of the fluid through different graphs are explained. In this process, certain iterations were performed for different step sizes in the direction of η = 0 . 01 and x = 0 . 005 , respectively. So, keeping this in view to get the more accurate results with all parameters considered, 0 ≤ M ≤ 1 , 0 ≤ R d ≤ 1 , 0 ≤ Q ≤ 1 , 0 . 01 ≤ α ≤ 0 . 04 , 0 ≤ L e ≤ 40 , 0 . 1 ≤ N b ≤ 0 . 7 , 0 . 1 ≤ N t ≤ 0 . 7 , 0 . 1 ≤ N r ≤ 0 . 7 , 0 . 1 ≤ E c ≤ 0 . 4 , 0 . 1 ≤ J ≤ 0 . 4 , . The obtained results illustrate that Nusselt number, Sherwood number, and velocity profile decreases respectively with the increase of waviness amplitude, but skin friction changes its behaviour to wavier. Also, temperature and concentration profiles increase respectively with enhancing the value of the amplitude of waviness. Finally, it is noted that Nusselt number and Sherwood number decrease for higher values of the Brownian parameter. But after a specific value of x, the trend of Sherwood number increases. However, the behaviour of skin friction decreases, but in a precise manner, it remains almost unchanged.

Impact of radiation absorption on chemically reactive and heat generating drilling liquids comprising of water-clay, kerosene-clay or engineoil-clay nanofluids flowing through a vertical channel is considered. Applications are found in rig drilling process for the convective transport of constituent materials up to the surface by the fluid. It is presumed that the cold and hot parallel walls are maintained at different uniform temperatures, but with unequal slip factors. One of the slippery heated walls is stationary while the other stretches linearly. The partial differential equations are scaled to ordinary equations in tandem with the physical boundary conditions, and evaluated through homotopy perturbation method. Certification is accredited via data comparison with numerical results using shooting method. Among others, the results of this investigation suggest that the concentration and temperature distributions dip due to larger radiation absorption and viscosity parameters with or without the suction, velocity slips, and the chemical reaction parameters.

Recent advancements in nanotechnology research have introduced hybrid nanofluids which are sophisticated classes of fluids with enhanced thermal properties that outperform conventional nanofluids. The objective of current communication is to illustrate the comparative mathematical model of MHD hybrid nanofluid and mono-nanofluid flows with heat flux condition through a stretching sheet. Impact of melting phenomenon, heat generation/absorption and natural convection is considered. The thermal radiation, viscous dissipation and temperature-dependent viscosity are also considered. In current model, two different nanoparticles namely zinc oxide ( ZnO ) and zirconium dioxide ( ZrO 2 ) are dispersed in kerosene oil ( C 10 H 22 ) base fluid to form a hybrid nanofluid. Similarity transformations are utilized to renovate the governing PDEs structure system into ordinary ones. The numerical computations of current mathematical model are computed through bvp4c built-in function in MATLAB with shooting scheme. The fluctuations of velocity and temperature distributions are analyzed with physical impacts for different flow parameters. It is visualized that the growing amount of convection parameter corresponds to increment in velocity profile. The velocity of hybrid nanofluid reduces as the magnetic parameter increases. It is analyzed that the thermal field of hybrid nanofluid is an increasing function of thermal radiation parameter. Furthermore, the thermal profile is a reducing function of melting and Prandtl numbers.

An unsteady Casson nanofluid with a stagnation point is considered along a radiated stretching surface depending on the heat source and convective condition. Moreover, the influence of magnetic field and the wall suction is considered with the slip condition. In view of these assumptions, a system of nonlinear partial differential equations (PDEs), have been formulated which are primarily converted to the dimensionless ordinary differential equations (ODEs). The MATLAB function bvp4c has been used to solve the resulting system of the ODEs. The resulting solutions have been determined as expressed by the velocity, friction drag, concentration, temperature, mass transfer and heat transfer of the nanofluids which are obtained under the influence of associated flow parameters. It is observed that the Sherwood number and the fluid concentration respectively enhances and decreases for the escalating values of the Brownian motion parameter and the Schmidt number although a reverse of these cases have been observed for the escalation of Thermophoresis parameter. In the same way, the skin friction coefficient enhances for the escalation of Casson parameter, suction parameter, and the Hartmann number whereas the rate of heat transfer declines for the growing values of Eckert number and enhances for the higher values of suction and thermal radiation. Additionally, the fluid temperature is boosting for the growing values of Biot number, Eckert number and heat generation parameter, whereas the velocity is diminishing for the growing values of Casson parameter and unsteadiness parameter though it is boosting for the growing values of suction parameter.

This study investigates the mathematical modelling of heat generation/absorption effect on the convective flow of single wall carbon nanotube-copper (SWCNT-Cu)/water hybrid nanofluid towards a stagnation point past a stretching sheet with Newtonian heating. The set of governing equations in the form of non-linear partial differential equations are first transform using the similarity transformation technique then solved numerically by the Runge-Kutta-Fehlberg (RKF45) method in Maple software. The numerical solutions were obtained for the surface temperature, the heat transfer coefficient and the skin friction coefficient as well as the velocity and the temperature profiles. The features of the flow and heat transfer characteristics for various values of the stretching parameter, the conjugate parameter, the nanoparticle volume fraction parameter and the heat source/sink parameter are analyzed and discussed. It is found that effects of hybrid nanoparticles are more significant for lower stretching parameter and for large conjugate parameter values, as well as the heat generation/absorption.

This research article looks at entropy generation and activation energy analysis on hydromagnetic and thermally radiated nanofluid flow generated by a nonlinearly stretching sheet of variable thickness considering heat generation, mixed convection, velocity slip, viscous dissipation, thermal slip, binary chemical reaction and Ohmic dissipation aspects. Governing model equations of continuity, momentum, energy and concentration are converted into ODEs by employing appropriate similarity transformations. The resulting coupled highly nonlinear equations have been solved numerically with the help of the Runge–Kutta–Fehlberg method-based shooting technique. Results obtained for a particular case of the current fluid flow problem are in good agreement with the existing results. The graphical outcomes are discussed for velocity, temperature, entropy generation and concentration regarding various controlling parameters. The impacts of different controlling parameters on the local skin-friction coefficient, local Nusselt and Sherwood numbers are also analyzed and the numerical results are presented in tabular form. The obtained results reveal a reduction in entropy generation for growing values of magnetic and temperature ratio parameters near the solid surface, while a reverse effect is noticed for power-law index and Brinkmann number.

The present article analyzes the effect of viscous dissipations on natural convection heat transfer. The power law model for non-Newtonian fluid with heat generation or absorption effect along a sinusoidal wavy surface with isothermal boundary condition is investigated. A simple coordinate transform is employed to map the wavy surface into a flat surface, and also, the fully implicit finite difference method is incorporated for the numerical solution. The findings of this study can help better understand the effect of parameters such as the Brinkman number, heat generation/absorption, wave amplitude magnitude, and generalized Prandtl number on convective heat transfer in dilatant and pseudoplastic non-Newtonian. Results show that as the Brinkman number increases, the amount of heat transfer decreases. This is physically justifiable considering that the fluid becomes warmer due to the viscous dissipation, decreasing its temperature difference with the constant temperature surface. Also, the effect of the power law viscosity index is surveyed. It is demonstrated that the magnitude of the local Nusselt number in the plane leading edge has the smallest quantity for pseudoplastic fluids compared to dilatant Newtonian fluids. Additionally, as the distance from the plane leading edge increases, the heat transfer declines.

The purpose of the present work is to investigate the effect of the angle of application of magnetic field in two types of uniform and non-uniform on the nanofluid flow characteristics and natural convection heat transfer in the presence of uniform heat generation. This numerical study was performed using multi relaxation time lattice Boltzmann method (MRT-LBM). The D2Q9 and D2Q5 grid arrangements were used to simulate the flow and temperature fields, respectively. The results show that in all cases, increasing the strength of magnetic field (the Hartmann number) reduces the average Nusselt number, which increases with increasing the heat generation coefficient. Applying a magnetic field horizontally results in an average of about 15% lower Nusselt number compared to the vertical. Increasing the strength of magnetic field (the Hartmann number) and the average Nusselt number is achieved by periodically applying a magnetic field instead of applying a uniform one. As the aspect ratio of the cavity increases, the non-uniform effect of applying a magnetic field becomes more apparent.

In this article, we examined the magnetized flow of ethylene glycol- 50 − 50 % water-based nanoliquids comprising molybdenum disulfide ( MoS 2 ) across a stretching sheet. Flow properties were examined under the impacts of magnetic field and thermal radiation. The behavior of heat generation/absorption is also accounted. Similarity transformations are used on the system of PDEs to get nondimensional ODEs. The obtained nondimensional ODEs are solved with the help of the Runge–Kutta–Fehlberg method via computational software MATHEMATICA. The behavior of prominent parameters for velocity and thermal profiles is plotted graphically and discussed in detail. It is depicted that the temperature field is upgraded with increase in the heat generation/absorption parameter. Furthermore, a larger Schmidt number causes reduction in the concentration field. The current formulated model may be useful in biomedical engineering, biotechnology, nanotechnology, biosensors, crystal growth, plastic industries, and mineral and cleaning oil manufacturing.

The application of combined electric and magnetic fields is proposed for better heat transfer enhancement in a porous fin system. An inverse estimation technique is established to simultaneously de...

Chamfered inserts have found broader applications in metal cutting process especially in high-performance machining of hard-to-cut materials for their excellent edge resistance and cutting toughness. However, excessive heat generation and resulting high cutting temperature eventually cause severe tool wear and poor surface integrity, which simultaneously limits the optimal selection of machining parameters. In the present study, an analytical thermal–mechanical model is proposed for the prediction of the three-dimensional (3-D) temperature field in cylindrical turning with chamfered round insert based on a modified slip-line field approach. First, an innovative discretization method is introduced in a general 3-D coordinate system to provide a comprehensive demonstration of the irregular cutting geometry and heat generation zones. Then, a plasticity-theory-based slip-line field model is developed and employed to determine the intensities and geometries of every elementary heat sources in Primary Deformation Zones (PDZ), Secondary Deformation Zones (SDZ) and Dead Metal Zones (DMZ). At last, a 3-D analytical model is suggested to calculate the temperature increases caused by the entire heat sources and associated images. The maximum cutting temperature region predicted is found existing upon the chip-tool contact area rather than the tool edge. Moreover, the rationalities of cutting parameters employed are analyzed along with theoretical material removal rates and ensuing maximum cutting temperatures. The results indicate that the cutting conditions with large depth of cut and high cutting speed are more desirable than those with high feed rates. The proposed models are respectively verified through a series of 3-D Finite Element (FE) simulations and dry cutting experiments of Inconel 718 with chamfered round insert. Satisfactory agreement has been reached between the predictions and simulations as well as the measurements, which confirms the correctness and effectiveness of the presented analytical model.

Involvement of hybrid nanoparticles a vital role to improve the efficiency of thermal systems. This report covers the utilization of different nanoparticles mixed in Carreau Yasuda material for the improvement of thermal performance. The configuration of flow situation is considered over a rotating porous cone by considering the Hall and Ion slip forces. Transport of momentum is considered to be in a rotating cone under generalized ohm’s law and heat transfer is presented by considering viscous dissipation, Joule heating and heat generation. Rheology of considered model is derived by engaging the theory proposed by Prandtl. Modeled complex PDEs are reduced into ODEs under similarity transformation. To study the physics behind this phenomenon, solution is essential. Here, FEM (Finite Element Method) is adopted to compute the solution. Furthermore, the grid independent study is reported with several graphs and tables which are prepared to note the influence of involved parameters on thermal and velocity fields. It is worth mentioning that heat transport is controlled via higher radiation parameter and it upsurges for Eckert number. Moreover, Hall and ion slip parameters are considered significant parameters to produce the enhancement in motion of fluid particles but speed of nano and hybrid nanoparticles becomes slow down versus large values of Forchheimer and Weissenberg numbers. Additionally, an enhancement in production of heat energy is addressed via large values of heat generation number and Eckert number while reduction in heat energy is occurred due to positive values of thermal radiation and Hall and ion slip parameters.

Purpose The current investigation is communicated to analyze the characteristics of squeezed second grade nanofluid flow enclosed by infinite channel in the existence of both heat generation and variable viscosity. The leading non-linear energy and momentum PDEs are converted into non-linear ODEs by using suitable analogous approach. Design/methodology/approach Then the acquired non-linear problem is numerically calculated by using Bvp4c (built in) technique in MATLAB. Findings The influence of certain appropriate physical parameters, namely, squeezed number, fluid parameter, Brownian motion, heat generation, thermophoresis parameter, Prandtl number, Schmidt number and variable viscosity parameter on temperature, velocity and concentration distributions are studied and deliberated in detail. Numerical calculations of Sherwood number, Nusselt number and skin friction for distinct estimations of appearing parameters are analyzed through graphs and tables. It is examined that for large values of squeezing parameter, the velocity profile increases, whereas opposite behavior is noticed for large values of variable viscosity and fluid parameter. Moreover, temperature profile increases for large values of Brownian motion, thermophoresis parameter and squeezed parameter and decreases by increases Prandtl number and heat generation. Moreover, concentration profile increases for large values of Brownian motion parameter and decreases by increases thermophoresis parameter, squeezed parameter and Schmidt number. Originality/value No one has ever taken infinite squeezed channel having second grade fluid model with variable viscosity and heat generation.

The study of unsteady flow is essential in various engineering systems, for instance, the periodic fluid motion and start-up process. Therefore, this numerical study focuses on examining the unsteady magnetohydrodynamics (MHD) rear stagnation-point flow in Al2O3-Cu/H2O hybrid nanofluid past a permeable stretching/shrinking surface with the impact of heat generation/absorption. By choosing a suitable similarity transformation, partial differential equations are transformed into a system of nonlinear ordinary differential equations and solved using the bvp4c function in the MATLAB package. The effects of the solution domain’s operating parameters are analysed, and dual solutions are observable as the sheet shrinks. It is found that the addition of the suction parameter escalates the heat transfer efficiency. Eventually, the existence of the unsteadiness parameter and the heat generation/absorption effect significantly encourage heat transfer deterioration.

This research work highlight the newly developed concept of Rosseland approximation and gyrotactic microorganisms in steady, two-dimensional, incompressible flow of Walter's-B nanofluid (non-Newtonian) over a stretchable surface of sheet. Buongiorno nanofluid model, which represents seven important slip mechanisms (i.e., Brownian motion, inertia, Magnus impact, thermophoresis, diffusion-phoresis, gravity and fluid drainage) is utilized in the mathematical modeling of governing expressions. In this research work, only two important factors of seven slip mechanisms (Brownian diffusion, thermophoresis) are studied and the rest of neglected. Furthermore, the Rosseland approximation and heat generation/absorption effects are used in the modeling of the energy equation. The behavior of thermal and solutal stratification effects are addressed at the stretched boundary of the sheet. The nonlinear dimensional flow expressions lead to dimensionless ordinary equations through appropriate similarity transformations. The total residual error is calculated through Homotopy Analysis Method (HAM) for the momentum, temperature, concentration and motile density. The influences of important flow parameters of the governing flow equations are discussed and plotted graphically. The obtained results are compared with fruitful and valuable research in the literature and found very good agreement with them. Over obtained outcomes highlight that the velocity field, declined versus higher estimations of Weissenberg number. It is also remarked that the temperature and concentration fields have contrast impact subject to thermophoresis parameter. The physical quantities like skin friction coefficient, motile density, concentration and Nusselt number are discussed physically via various flow parameters.

The thermal characteristics of a battery are vital in order to understand its health and safety. The thermal characteristics are influenced by charging techniques. This paper presents theoretical explanation, experimental validation, and an analytical method to quantify the heat loss influenced by charging techniques for a Li-Ion battery. Constant current constant voltage (CC-CV), sinusoidal ripple current constant voltage, and pulse current constant voltage charging profiles are used as test cases for validation. The electrical and entropic heat generation for different charging profiles are modeled and estimated based on battery equivalent parameters. The estimated heat generation is compared with the heat flux measurement from a differential scanning calorimeter. In addition to the heat flux measurement, temperature, state of charge, terminal voltage, and current were recorded and analyzed.

Heat generation during the Kirschner wire (K-wire) insertion process, under either unidirectional or oscillatory drilling mode, places bone at risk of thermal osteonecrosis which can lead to infection. There is a lack of quantitative understanding of the heat generation difference between the two drilling modes and knowledge of optimal thrust force level under each mode is missing. The goal of this study is to investigate the effects of drilling modes and thrust force levels on the bone drilling outcomes. Controlled machine-based constant thrust force K-wire insertion experiments were conducted with key process parameters monitored and compared quantitatively. Statistical analysis showed that the oscillatory mode consumed 2.6 times more electricity than the unidirectional mode but generated 53% less thermal energy and 23% lower peak temperature. However, the oscillation also led to 18% higher peak torque in the transient drilling stage and 23% shallower drilling depth. The optimal choice of the drilling mode depends on specific surgical needs to minimize bone damage (control of peak temperature vs. exposure time and torque control). Heat generation was dominated by the torque and corresponding rotational power under both modes. To minimize the bone temperature while keeping high drilling speed efficiency, a moderate thrust force is preferred under the unidirectional mode to balance between feed force and compressed debris resistance. For oscillatory mode, a small thrust force to keep the K-wire engaged with the bone is optimal.

The present article concerns the analysis of the heat transport mechanism in the hydromagnetic flow of nanoparticles on an oscillating curved stretching surface. The features of heat transfer are examined by considering the Joule heating effects along with melting heat transfer. Furthermore, the impacts of heat generation are additionally incorporated within the energy equation. The mathematical formulation undertaking the aforesaid flow scheme is established in the form of partial differential equations by employing curvilinear coordinate systems. The series solution of the formulated flow equations is obtained by utilizing a proficient analytical approach entitled as Homotopy analysis method (HAM). A parametric analysis is carried out for the various involved flow parameters such as dimensionless radius of curvature, the proportion of the oscillation frequency of the surface to its stretching rate parameter, nanoparticles, magnetic and heat generation parameter, Prandtl and Eckert number, on the flow, temperature, and pressure fields are displayed through graphs. Also, a comparison between the achieved results with the reported data in the literature for the flat oscillating surface is found in good agreement.

In the present investigation, a numerically driven direct and inverse study is conducted for the simultaneous prediction of the internal heat generation, electric field, and magnetic field strengths in porous pin fins from the surface temperature profile in electronic cooling applications. Consideration under imposed electrical and magnetic fields along with all modes of heat transport is given. Initially, duly-verified forward solutions are generated for the calculation of the temperature profile, and subsequently, three unknown parameters are predicted at the same time using the inverse methodology assisted by the artificial bee colony (ABC) algorithm. Here, numerical case studies have been presented to discover a suitable relation between the three parameters estimated by the ABC methodology. The current research envisages that even though a wide range of probable parametric combinations exist sustaining the prescribed thermal profile, however, the magnetic field parameter mostly governs the thermal phenomenon, while, the effect of mutual interplay among the electrical field and internal heat generation parameters is responsible for the temperature distribution under a given measurement error. Even with the influence of random perturbations, the ABC-assisted inverse methodology is observed to precisely simulate and determine the required thermal criterion and establish the available thermal field within the 4.55% error margin. Toward meeting a necessary heat transfer rate from porous pin fins, the proposed strategy is claimed to be valuable for appropriately controlling the electric and magnetic fields along with the indefinite state of interior heat generation rate.

Superconducting cables have been developed around the world and demonstrated its operation in the grid. One of the important subjects is to study what happens in case of fault events, such as a ground fault, short circuit fault and so on, occurred in the superconducting cable. Therefore, we have conducted experimental and numerical simulations at the fault events. For the short circuit accidents, we conducted experimental simulation with a 66 kV 3-core cable in 40 m length to measure LN2 temperatures and pressures in the cable during and after simulated fault current as 16 kA- 8 sec, which has the same heat generation as the worst fault condition in the Japanese 66 kV network as 31.5 kA for 2 sec. The measured values of temperature and pressure are almost good agreement with calculated values. Using the same calculation code, temperatures and pressures at the fault event are estimated in the superconducting cable with 3 km length for practical use. As the results, in case of 31.5 kA in 2 sec, maximum temperature at superconducting conductor is calculated as 112 K and maximum pressure is as 3 MPa under the base pressure of 1 MPa. In that case, no gasification of LN2 is occurred. So, blowout of cryostat would not be occurred. However, it expects that several hours are necessary to turn back original state. For the ground fault, we conducted experimental simulations using samples with protection sheets and short cable samples. The fault current condition is assumed as 1.5 kA for 2 sec, which is the worst case in the Japanese 66 kV network. In such condition, the cable cryostat can be penetrated by the arc energy of the insulation break down and then LN2 would be blown out to make some damage for surrounding apparatus. So, we conducted LN2 leakage test in the manhole to measure LN2 accommodation level and concrete temperatures. Using experimental results and diffusion equation with thermal conductivity of concrete, inner pressure of manhole was simulated. The calculation results show the pressure rising is not so fast that the manhole lid can be blown off.

In this article, an unsteady free convection flow of MHD viscous fluid over a vertical rotating plate with Newtonian heating and heat generation is analyzed. The dimensionless governing equations for temperature and velocity fields are solved using the Laplace transform technique. Analytical solutions are obtained for the temperature and components of velocity fields. The obtained solutions satisfy the initial and boundary conditions. Some physical aspects of flow parameters on the fluid motion are presented graphically.

The problem of laminar boundary layer flow of power-law fluid over a continuous moving surface in the presence of a transverse magnetic field with velocity slip was investigated. The governing partial differential equations for the flow and heat transfer were transformed into non-linear ordinary differential equations using the similarity method. These equations were solved numerically by applying the fourth-order Runge-Kutta method with a shooting technique. The solution is found to be dependent on various parameters such as power-law index, magnetic field parameter, suction, and injection parameters. The effect of various flow parameters in the form of dimensionless quantities on the flow field is discussed and graphically presented. It was observed that an increase in the magnetic property results to a decrease flow of fluid velocity and also, an increase in the Prandtl number results to an increase in the rate of heat transfer.

This work examines the entropy generation with heat and mass transfer in magnetohydrodynamic (MHD) stagnation point flow across a stretchable surface. The heat transport process is investigated with respect to the viscous dissipation and thermal radiation, whereas the mass transport is observed under the influence of a chemical reaction. The irreversibe factor is measured through the application of the second law of thermodynamics. The established non-linear partial differential equations (PDEs) have been replaced by acceptable ordinary differential equations (ODEs), which are solved numerically via the bvp4c method (built-in package in MATLAB). The numerical analysis of the resulting ODEs is carried out on the different flow parameters, and their effects on the rate of heat transport, friction drag, concentration, and the entropy generation are considered. It is determined that the concentration estimation and the Sherwood number reduce and enhance for higher values of the chemical reaction parameter and the Schmidt number, although the rate of heat transport is increased for the Eckert number and heat generation/absorption parameter, respectively. The entropy generation augments with boosting values of the Brinkman number, and decays with escalating values of both the radiation parameter and the Weissenberg number.

Purpose In heat transfer, fluids and nanoparticles can provide new innovative technologies with potential to adapt the heat transfer fluid’s thermal properties through control over particle size, shape and others. This paper aims to examine the effects of spherical and non-spherical (cylinder, disk, platelets, etc.) shapes of silver (Ag) nanoparticles on heat transfer enhancement and inherent irreversibility in hydromagnetic water base nanoliquid flow over a convectively heated stretching sheet with heat generation/absorption. Design/methodology/approach Applying suitable similarity constraints, the model partial differential equations are transformed into a set of nonlinear ordinary differential equations. Solutions are obtained analytically via optimal homotopy asymptotic method (OHAM) and numerically via shooting technique coupled with the Runge-Kutta-Fehlberg (RK-F) method. Findings The impact of Ag nanoparticle’s shape along with other germane factors, such as Biot number, magnetic field, solid volume fraction and heat source/sink on velocity and thermal profiles, Nusselt number, skin friction coefficient, heat transfer enhancement, rate of entropy generation and irreversibility ratio, are scrutinized via graphical simulations and discussed. This study revealed that cylindrical shape Ag nanoparticles generate high entropy and fluid friction irreversibility, whereas disk shape Ag nanoparticles exhibit high transfer enhancement rate. Moreover, a boost in magnetic field intensity, volume-fraction parameter and Biot number enhances the thermal boundary layer thickness. Originality/value The main objective of this work is to examine the different Ag nanoparticles shape effects on the heat transfer enhancement and inherent irreversibility owing to hydromagnetic nanoliquid flow past a convectively heated stretching sheet with heat source/sink, which has not been yet studied. It is hope that this study will bridge the gap in the present literature and serve as impetus to scholars, engineers and industries for more exploration in this direction. The intrinsic nonlinearity of the model equations precludes its exact solution; hence, OHAM and shooting technique coupled with the RK-F method have been used to numerically tackle the problem. Pertinent results are discussed quantitatively and displayed graphically and in tabular form.

In this article, the effect of electromagnetic force with the effect of thermal radiation on the Williamson nanofluid on a stretching surface through a porous medium was studied considering the effect of both heat generation/absorption and Joule heating. On the other hand, the effect of Brownian motion and thermophoresis coefficients was considered. The system of nonlinear partial differential equations governing the study of fluid flow has transformed into a system of ordinary differential equations using similarity transformations and nondimensional variables which were subsequently solved numerically by using the Rung-Kutta fourth-order method with shooting technique. Moreover, the effect of the resulting physical parameters on the distributions of velocity, temperature, and concentration of nanoparticles has been studied by using graphical forms with an interest in providing physical meanings to each parameter. Finally, special diagrams were made to explain the study of the effect of some physical parameters on the skin friction coefficient and the local Nusselt number; these results led to reinforcement in the values of the skin friction coefficient for the increased values of the magnetic field and the Darcy number while the effect on the local Nusselt number by thermal radiation as well as the heat generation/absorption coefficients became negative.

Purpose Under-race lubrication can increase the amount of lubricating oil entering a bearing and greatly improve lubrication and cooling effects. The oil-air two-phase flow and heat transfer characteristics inside a ball bearing with under-race lubrication play a key role in lubrication and cooling performance. The purpose of this paper is to study these two characteristics, and then provide guidance for lubrication and heat dissipation of bearing with under-race lubrication. Design/methodology/approach In this paper, a simplified three-dimension heat transfer model of ball bearing with under-race lubrication is established; the coupled level set volume of fluid method is used to track the oil-air two-phase flow, and the Palmgren method is used to calculate the heat generation. The influence of rotation speed and inlet velocity on oil volume fraction, temperature and convection heat transfer is investigated. A temperature test for under-race lubrication is carried out. Findings Because of the centrifugal force, lubricating oil is located more on the outer ring raceway. As the rotation speed decreases and the inlet velocity increases, the oil volume fraction increases and the temperature decreases. Furthermore, the area with high oil volume fraction has a large convection heat transfer coefficient and low temperature. The error between the simulation temperature and the test temperature is within 10%. Originality/value The research on the temperature field and convection heat transfer characteristics of under-race lubrication ball bearings at different rotation speeds and inlet velocities is rarely involved.

To predict the parameters of the quality of the processed parts and the period of durability of the cutting tool, mathematical models are needed that will allow us to calculate not only the mathematical expectation of the parameters of the machining process, but also the dispersion of these parameters. The working capacity of the tool and the quality parameters of the parts depend significantly on the temperature on the contact surfaces of the tool, as well as on the surface of the workpiece. Mathematical dependences for calculating the components of the total heat generation capacity during turning are given. It is assumed that the yield stress, which determines the cutting and friction forces on the contact surfaces of the cutter, workpiece and chip, depends on the temperature in the area of plastic deformation. The heat transfer at the boundaries of objects in contact with the process fluid or air is given in the form of the Newton-Richman law. The equations of thermal conductivity of contacting objects were solved together with the general boundary conditions in the contact zone, using the finite element method. The results of numerical simulation of the main component of the cutting force and temperatures in the contact zones of the face of the cutter with the chips and the fiank surface with the workpiece, depending on the yield strength of the workpiece material, are presented. The values of fluctuations in the cutting force and contact temperatures depending on the spread of the yield stress of the workpiece material during turning of workpieces made of 45 and 12X18H10T steels are determined. Based on the results of numerical modeling, regression equations are obtained for calculating the tangential component of the cutting force, the temperatures on the face and flank surfaces of the cutter, and the temperature on the surface of the workpiece.

This paper focuses on a numerical investigation of steady two-dimensional natural convection and volumetric radiation interactions in a concentric annulus between two square isothermal cylinders. T...