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Exertional heat stroke (EHS) is a true medical emergency with potential for organ injury and death. This consensus statement emphasizes that optimal exertional heat illness management is promoted by a synchronized chain of survival that promotes rapid recognition and management, as well as communication between care teams. Health care providers should be confident in the definitions, etiologies, and nuances of exertional heat exhaustion, exertional heat injury, and EHS. Identifying the athlete with suspected EHS early in the course, stopping activity (body heat generation), and providing rapid total body cooling are essential for survival, and like any critical life-threatening situation (cardiac arrest, brain stroke, sepsis), time is tissue. Recovery from EHS is variable, and outcomes are likely related to the duration of severe hyperthermia. Most exertional heat illnesses can be prevented with the recognition and modification of well-described risk factors ideally addressed through leadership, policy, and on-site health care.

In this paper, an enhanced thermal model is proposed for pouch batteries, which can be used for a battery management system (BMS) at low temperatures and high current rates. This thermal model integrates a virtual resistance model (VRM) and post resistance model at low temperatures. Firstly, based on the Arrhenius equation, the resistance model at low temperatures (from 0 °C to -10 °C) and high discharge rates (from 3.125C to 12.5C) is extrapolated from the resistance model under room temperature conditions. In this context, the resistance model at low temperatures is regarded as the VRM. In comparison to the experimental results, the maximum error of this VRM is 0.851 mΩ. Additionally, the equivalent post resistance model of the pouch battery, including that of the positive electrode and negative electrode, is also given for low temperatures. Finally, the complete thermal model for pouch batteries is validated at low temperatures and high discharge rates. The temperature evolution at different points on the battery, along with the heat generation properties of the battery, are simulated under cyclic pulse current and constant current working conditions. For cyclic pulse current, the maximum mean error in terms of temperature evolution is 0.72 °C, and for constant current working conditions, the maximum mean error is 0.79 °C.

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.

The formulation presented in this paper is for the performance analysis of a primary lithium-carbon monofluoride cell. The formulation can also be used to compute the theoretical cell open-circuit voltage; the fractional conversion of the limiting reactant, carbon monofluoride and hence, the cell fractional state-of-charge; total amount of charge required to be involved for the complete utilization of the cell cathode active material, carbon monofluoride as well as the transient specific amount of charge involved; the ratio of the thermal energy production to the electric energy production; and the rate of heat exchange between the cell exterior surface and its surroundings required for the determination of the cell average temperature.

The impacts of MHD and heat generation/absorption on lid-driven convective fluid flow occasioned by a lid-driven square enclosure housing an elliptic cylinder have been investigated numerically. The elliptic cylinder and the horizontal enclosure boundaries were insulated and the left vertical lid-driven wall was experienced at a fixed hot temperature, and the right wall was exposed to a fixed cold temperature. COMSOL Multiphysics 5.6 software was used to resolve the nondimensional equations governing flow physics. A set of parameters, such as Hartmann number ( 0≤𝐻𝑎≤50 ), Reynolds number ( 10^2≤𝑅𝑒≤10^3 ), Grashof number ( 10^2≤𝐺𝑟≤10^5 ), heat generation-absorption parameter ( −3≤𝐽≤3 ), and elliptical cylinder aspect ratio (AR) ( 1.0≤𝐴𝑅≤3.0 ) have been investigated. The current study discovered that for low Reynolds number, the adiabatic cylinder AR of 2.0 provided the optimum heat transfer enhancement for the model investigated, also the impact of cylinder size diminishes beyond Gr = 10^4. But for high Reynolds (Re = 1000), the size of the cylinder with AR = 3.0 offered the highest heat transfer augmentation. The clockwise flow circulation reduces because of an increase in AR, which hinders the flow circulation. In addition, heat absorption supports heat transfer augmentation while heat generation can suppress heat transfer improvement.

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...

Brush seals are leakage performance systems that are operating against turbine shafts and bucket tips. Flexible bristle structure can compensate the rotor interference during transients, which enables closer clearance control in turbine and turbo-engine applications. During turbomachinery transients, contacting bristles exert force on turbine shaft, which in turn result in wear, frictional heat generation, counter torque and power loss. Brush seal design with proper stiffness has crucial importance since high bristle tip force levels during rotor contact may result in rotor instability, bristle tip melting or thermo-mechanical fatigue due to large amount of local frictional heat input. Counter torque applied by the contacting brush seal with improperly excessive tip force may result in turbine stall and overall efficiency losses. High levels of bristle contact forces may induce elevated wear rates, which degrades the leakage performance of the brush seal during its life cycle. Brush seal contact force evaluation under operating conditions has critical importance and has to be conducted before turbine integration to avoid performance losses and possible turbine failure in some extreme cases. In this paper, ‘Bristle Contact Force Theory’ is developed and closed form bristle tip force (BTF) function is derived where rotor-bristle, inter-bristle and bristle-back plate interactions are included. BTF measurements under pressurized and unpressurized air environment are conducted for the selected test seals by using the custom ‘Rotary Test Rig’. BTF function of bristle contact force theory show high level of correlation with the test data. The effect of cant angle manufacturing tolerance on bristle tip force levels is also examined through bristle tip contact force theory, and compared with the test seal measurements. Methodology for number of bristle row calculation and comparison with the geometric inspection of test seals are also detailed within the content of this paper.

Geological repository of high-level nuclear waste (HLNW), the most feasible approach for the safe and permanent treatment of HLNW without human intervention, has been investigated for years by many researchers. In some countries, real facilities for the geological repository are already under construction. In Japan, however, due to complicated geologic conditions, especially underground water and fractured rock masses, and the high risk of natural disasters, ensuring the long-term stability of the method remains a struggle. The influential factors include underground water, heat generation from radioactive waste, and thermal and chemical weathering of the surrounding rock mass as a natural barrier. It is difficult to estimate and verify the long-term stability for up to one hundred thousand years, a complicated thermal–hydraulic-mechanical-chemical coupling behavior, via any field test. The objective of the study is to develop a numerical method for predicting the long-term stability of geological repositories. As the first step toward realizing this objective, heating and loading tests on cave model made of man-made rock specimens that are composed of diatoms, gypsum, and water, which are viscoplastic materials, were conducted, based on which a newly proposed numerical method with finite element method (FEM) was used to describe the thermal, mechanical, and time-dependent behavior of the model tests for a geological repository. To ensure the accuracy of the numerical calculations, all the material parameters in the thermoelasto-viscoplastic model with consideration of overconsolidation, the structure, and the influence of intermediate stress were determined via triaxial compression/creep tests under various temperatures, confining stresses, and loading rates. Finally, the validity of the numerical method was demonstrated by model tests over a limited time span.

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.

At low operating temperatures, the power capability and charging/discharging capacity of lithium-ion (Li-ion) batteries can decay rapidly. Therefore, it is essential to preheat the Li-ion batteries in advance of the normal operations of a battery electric vehicle. High-frequency AC preheating methods are advantageous to achieve a miniaturized and lightweight design. In this paper, a self-heating circuit topology is used for studying the characteristics of Li-ion batteries at low temperatures and under high-frequency AC excitation. The thermal behaviors of Li-ion batteries under high-frequency AC excitations are comprehensively analyzed with an improved heat generation model. Experimental results exhibit that heat generation due to electrochemical reactions has a significant influence on self-heating rates under the high-frequency AC excitation, and the heating rate is positively correlated with the current frequency and root-mean-square (RMS) value. Specifically, when the current frequency is 90 kHz and the RMS value is 3.51 A or 1.17C, validated by experiment and numerical simulation, a 2.9Ah 18650 Li-ion cell can be heated up from -20 °C to 5 °C in 7.33 min with an average electrochemical heat generation of 2.962 W.

This work reports the fabrication of AuNR@MSNs [i.e., gold nanorods (AuNRs) coated with mesoporous silica nanoshells (MSNs)] with independent sensitivities to pH and near-infrared (NIR) light for reversible on–off switching of drug release without premature drug leakage. The fabrication involves the incorporation of lauric acid (LA) as a thermosensitive gatekeeper, followed by the coating of tannic acid (TA) layers as a pH-sensitive gatekeeper. The protonation–deprotonation of the TA layers according to change in pH can result in their swelling–deswelling to induce pH-sensitive drug release, while the solid–liquid phase transition of LA by NIR light-induced heat generation in AuNRs enables the NIR light-controlled release of preloaded drug molecules. The interplay between these dual gatekeepers allows the release of pre-loaded drug from the AuNR@MSN-LA@TAs (i.e., AuNR@MSNs incorporating LA and TA) only at acidic conditions under NIR light irradiation, without premature drug leakage under inactive conditions (neutral pH or no NIR light). Moreover, the reversibility of the gatekeepers can make an on–off mannered drug release. Benefiting from the capability of the gatekeepers to induce pH-/temperature-sensitive release, along with the photothermal ability of AuNRs, the AuNR@MSN-LA@TAs can exhibit a satisfactory anticancer performance without undesired drug leakage.

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.

Objective Laparoscopic renal denervation (LRDN) ablates sympathetic nerves on the outer wall of a renal artery to treat autonomic nervous system disorders such as hypertension and arrhythmia. Here, we developed a new circular radio frequency (RF) electrode for LRDN using micro-electro-mechanical systems (MEMS) technology. Methods The electrode consists of a parallel bipolar MEMS electrode, two MEMS thermocouples, and a shape-memory alloy (SMA) substrate. The electrode is automatically wrapped and unwrapped under actuation controlled by the heat generated by RF energy on the electrodetissue interface. The electrode was designed through a computational simulation analysis, and its actuation and temperature-sensing performance were tested in laboratory experiments and a porcine animal study. Results In an in-vivo study of porcine renal arteries, the electrode could automatically wrap and unwrap around an artery during LRDN. The bipolar MEMS electrode required 13 Vrms for heat generation up to 60 C, while the two MEMS thermocouples reliably measured the temperature without noise signals (a temperature coefficient of 38.3 or 38.5 V/C and an accuracy of 0.44 or 0.49 C). As revealed in a histological analysis using hematoxylin and eosin staining and Massons trichrome staining, the renal artery was intact after LRDN. Conclusion The circular RF electrode improves the safety of LRDN by reliably measuring the electrode temperature of the electrode during RDN and enhances the effectiveness of LRDN by reducing the complicated manipulations of the surgical instrument. Significance The developed circular RF electrode will pave the way for LRDN treatment of autonomic nervous system disorders.

Thermal management of electrical machines is an important issue to improve electromagnetic performance, reduce system size and prolong lifetime. Based on the equivalent thermal circuit (ETC) and computational fluid dynamics (CFD) methods, the temperature rise characteristic of a high-speed stator-permanent magnet-type flux switching (HS-SPMFS) machine for fuel-cell electric vehicle compressor is predicted. Firstly, the structural features, key dimensions, material properties and heat generation rate of the HS-SPMFS machine and its cooling system are introduced. Secondly, the ETC model of the machine with a liquid cooling channel is proposed, and the size of the cooling system is preliminarily designed. The influence mechanism of the number, size and flow rate of the water channel on the convective heat transfer area, convective heat transfer coefficient, water head loss and winding temperature rise is revealed. On this basis, combined with the CFD method, the temperature distribution of the machine is studied, and the detailed temperature distributions of each component of the machine are obtained and verified by the ETC method considering the cooling system. Finally, a HS-SPMFS machine prototype is manufactured and the temperature test platform of the prototype is built. The temperature rise behaviors of the machine under different working conditions are tested, verifying the theoretical analysis and the prediction methods.

Boilers are one of the most used units for both heat generation plants and industry systems. Their operation is subjected to different working loads and maintenance requirements. Exploitation experience points out critical boiler zones where failures and break downs typically occur. This paper analyzes critical zones in hot water fire-tube boiler. Experimental procedure was performed on the model of this type of boilers and its critical element. The tube plate of hot water boiler was identified as the most critical one. Experimental analysis and numerical model verification were performed using Aramis system based on 3D Digital Image Correlation method. Numerical analysis was done in Ansys Software Package and verification of results was done based on measurements obtained by strain gauges and local measurements performed by the Aramis system. Stress-strain analysis indicates the critical zones of boiler tube plate. The character of change parameters such as strain and stress occurring in the critical zones can be verified both by experimental and numerical data. The paper presents a novel approach in experimental and numerical analyses that can be conducted in similar units and used for existing unit optimization, as well as for new product testing on different loads and provide opportunity for further development and improvement for practical industrial application.

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.

Burgeoning demand for machinability, health, and ecology, Environmental Protection Agency (EPA) regulations are pushing the modern manufacturing sector to apply dry or biodegradable cutting fluids, which are insufficient in the machining of difficult-to-cut materials. Therefore, this study is devoted to proposing a newly developed hybrid ethanol-ester oil lubri-coolant for machining titanium alloy. To encompass the effectiveness of the proposed cutting medium, the thermophysical properties (density, thermal conductivity, viscosity, specific heat), and tribological properties (friction coefficient, friction force), and investigated. Besides, the machinability performance of hybrid lubri-coolant is determined in terms of cutting temperature, cutting force, surface roughness, residual stresses, tool wear through minimum quantity lubrication (MQL) system in the high-speed machining of heat-treated Ti-6Al-4V. The machinability performance of hybrid lubri-coolant are compared to dry cuttings. Findings have depicted that density, viscosity, and thermal conductivity were decreased with the increase of temperature while specific heat was increased with the increase of temperature. Tribological characteristics showed the highest friction coefficient and friction force under dry conditions while minimum under hybrid ethanol-ester oil (1:1) conditions. The hybrid ethanol-ester oil lubri-cooling in milling showed lower cutting temperature, cutting force, surface roughness, residual stresses, and minimum tool wear results. The hybrid ethanol-ester oil is biodegradable, providing efficient cooling with the evaporation of ethanol, and lubrication due to long-chain ester oil molecules. The polar nature of ethanol and ester oil prevented microparticles adhesion and made a tribo-film on the tool-workpiece and prevented rubbing or frictional heat generation.

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.

When deep hole drilling problematic aluminum materials, the high ductility and adhesion tendency of these materials lead to the formation of built-up edges, long chips and material adhesions on the tool. This can not only cause rapid tool breakage, but also lead to significant damage to the borehole wall surface. In previous work, it has already been shown that these problems were avoided during vibration-assisted drilling with short tools. Compared to conventional drilling, in vibration-assisted drilling the feed motion is superimposed with a sinusoidal oscillation with a high amplitude and a low frequency resulting in a kinematic cut interruption and the generation of separated chips. The aim of this work is to investigate the extent to which the above mentioned problems encountered in conventional deep hole drilling of aluminum materials can be reduced by vibration-assisted deep hole drilling. To achieve this aim, experiments were carried out in conventional and vibration-assisted deep hole drilling. The chip geometry, feed forces, straightness deviation, surface temperatures and the surface quality of the borehole wall were used as evaluation criteria to compare both processes. It was demonstrated that the formation of built-up edges and material adhesions is avoided by vibration-assisted deep hole drilling. This results in a better surface quality of the borehole wall, what indicates less friction within the borehole due to the generation of small and separated instead of long chips. Since heat generation in vibration-assisted drilling is much lower than in conventional deep hole drilling, boreholes close to the workpiece surface were realized.

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.

A coupled optical-electrical-thermal modeling has been developed to investigate the heat generation and dissipation in Cu2ZnSn4SxSe4−x thin film solar cells. Five heat generation factors: Thermalization, Joule heat, Peltier heat, Surface Recombination heat, and non-radiative recombination heat (Shockley-Read-Hall and Auger) as well as two heat dissipation factors convective and radiative cooling were calculated and displayed in 2 and 3 dimensional maps. Thermalization is the dominant heat generation factor in the cell independent of the voltage. The non-radiative recombination heat and Joule heat depend on voltage. Apart from these bulk heating factors, the surface recombination heat and Peltier heat were also investigated. The surface recombination heat is higher at open-circuited voltage (V=Voc) compared to at V = 0 while the Peltier heat is zero at V=Voc which can be explained by looking at the energy band diagrams at these voltages. The total heat generation has a small gradient across the cell thickness (

To avoid thermal necrosis has always remained a challenge during trauma and orthopaedic (T&O) surgeries. Use of different coolants of liquid form like water, saline and gaseous form like Carbon dioxide and nitrogen are frequently used for the same. Though the factors responsible for temperature control related to drilling process like drilling parameters and drill specifications are important, the contribution of coolant in temperature control cannot be underrated. In this review work, the different aspects related to coolant supply like 1) effects of saline and water on different bone defects, 2) comparative effectiveness of internal coolant flow through step drill and conventional drill, 3) effects of irrigation volume and 4) significance of without cooling, external liquid cooling and internal gas cooling on temperature rise is made. The results show that, whereas, carbon dioxide is having specific heat capacity of 0.846 kJ/ kg-K and of nitrogen gas it is1.04 kJ/kg-K and of water it is 4.18 kJ/kg- K. So water solution has an improved cooling capacity than both of the gases CO2 and N2. But gases can be directly injected at the location of chip formation and so they also proved as a worthy alternative.

Machining of difficult to cut material at advanced range of process parameters is the requirement of modern day machining scenario for achieving the goals of sustainable machining through utilization of modern cooling techniques to minimizing the friction, heat generation and tool damage. Consequently, leads to profitable machining under the provision of suitable volume, application method and environmental friendly cutting fluids. Contrary to this, larger flow rate and inferior methodology of cutting fluid application leads to various health problems, environment issues and imperfect product quality. So, to achieve targets the sustainable machining, the firm has to meet certain environmental norms regarding the application and disposal of cutting fluids. Therefore, to tackle the aforementioned ecological issues the dry machining is preferred which exhibit solution, but this option does not endure economic plan at accelerated machining parameter levels due to lower tool life and impaired quality of product. Hence, the alternative to all these situations are the requirement of such a cooling system which does not pollute the environment, operator friendly as well as economical to use. Henceforth, the minimum quantity lubrication using soybean oil has been used in present investigation as a replacement to flood lubrication. The experiments have been conducted on EN-31 Steel taking advanced ranges of machining parameter in dry and M.Q.L system. Research outcomes revealed that the M.Q.L machining improved the surface finish, lowered the cutting temperature and enhanced the chip reduction coefficient with comparison to dry machining system. The Parametric optimization evaluated by TOPSIS approach pointed out that the best machining combination has been observed at 196 m/min, 0.088 mm/rev in vegetable oil environment.

AC homopolar motors, with high-temperature superconductors (HTS) are considered to be a promising technology for high-power applications. With superconducting components being placed exclusively in non-rotating parts, a motor can reach high rotational speeds. However, the dynamic behaviour of the system creates a non-negligible magnetic ripple field which generates heat and makes thermal management of the cryogenic system more challenging. In this paper we present a case study for the thermal behaviour of a conduction-cooled, high-temperature superconducting field coil assembly in a 500 kW asynchronous homopolar motor. The analysis focusses on the investigation of the magnetic ripple field and its impact on heat generation due to AC loss in the HTS field coil and eddy current loss in copper parts present in the assembly. Using electromagnetic and thermal finite-element models, we construct a detailed description of the thermal bus design which considers different cooling scenarios and sizing of the conductive elements. Depending on the geometry of the thermal bus, we observe heat loads from AC losses of up to 0.4 W, and eddy current losses in the copper elements of up to 1 W. These heat loads translate to temperature increases as high as 10 K. Techniques to reduce the temperature rise based on thermal bus redesign are presented, along with recommendations for the most promising cooling scenarios and optimal thermal bus geometry.

Controlled-source electromagnetic (CSEM) measurements are complementary data for magnetotelluric (MT) characterization although its methodology on land is not sufficiently developed and tested as in marine environments. Acquiring expertise in CSEM is crucial for surveys in places where MT cannot be performed due to high levels of cultural noise. To acquire that expertise, we perform CSEM experiments in the Vallès fault [Northeast (NE), Spain], where MT results have been satisfactory and allow us to verify the CSEM results. The Vallès basin is relevant for potential heat generation because of the presence of several geothermal anomalies and its nearby location in urban areas. In this article, we present the experimental setup for that region, a 2-D joint MT+CSEM inverse model, several 3-D CSEM simulations in the presence of metallic casing, and its comparison with real data measurements. We employ a parallel and high-order vector finite element algorithm to discretize the governing equations. By using an adapted meshing strategy, different scenarios are simulated to study the influence of the source position/direction and the conductivity model in a metallic casing presence. An excellent agreement between the simulated data and analytical/real field data demonstrates the feasibility of study metallic structures in realistic configurations. Our numerical results confirm that metallic casing strongly influences electromagnetic (EM) responses, making surface measurements more sensitive to resistivity variations near the metallic structure. It could be beneficial getting higher signal-to-noise ratios and sensitivity to deep targets. However, such a casing effect depends on the input model (e.g., conductivity contrasts, frequency, and geometry). This work was been developed in the frame of GEOURBAN project (PCI2018-092943 and PCI2018-093186). This work has received also partial funding from the European Union's Horizon 2020 programme under the Marie Sklodowska-Curie grant agreement N777778. Also, the research leading to these results has received funding from the European Union's Horizon 2020 programme, grant agreement N828947, and from the Mexican Department of Energy, CONACYT-SENER Hidrocarburos grant agreement N B-S-69926. Furthermore, this project has been 65% cofinanced by the European Regional Development Fund (ERDF) through the Interreg V-A Spain-France-Andorra program (POCTEFA2014-2020). POCTEFA aims to reinforce the economic and social integration of the French-Spanish-Andorran border. Its support is focused on developing economic, social and environmental cross-border activities through joint strategies favouring sustainable territorial development. The authors would like to thank the Editors-in-Chief and to both reviewers for their valuable comments and suggestions that helped to improve the manuscript’s quality. This work benefitted from the valuable suggestions, comments, and proofreading of Dr. Josep de la Puente (BSC).

Despite the unique ability of lanthanide-doped upconversion nanoparticles (UCNPs) to convert near-infrared (NIR) light to high-energy UV-vis radiation, low quantum efficiency has rendered their application unpractical in biomedical fields. Here, we report anatase titania-coated plasmonic gold nanorods decorated with UCNPs (Au NR@aTiO2@UCNPs) for combinational photothermal and photodynamic therapy to treat cancer. Our novel architecture employs the incorporation of an anatase titanium dioxide (aTiO2) photosensitizer as a spacer and exploits the localized surface plasmon resonance (LSPR) properties of the Au core. The LSPR-derived near-field enhancement induces a threefold boost of upconversion emissions, which are re-absorbed by neighboring aTiO2 and Au nanocomponents. Photocatalytic experiments strongly infer that LSPR-induced hot electrons are injected into the conduction band of aTiO2, generating reactive oxygen species. As phototherapeutic agents, our hybrid nanostructures show remarkable in vitro anticancer effect under NIR light [28.0% cancer cell viability against Au NR@aTiO2 (77.3%) and UCNP@aTiO2 (98.8%)] ascribed to the efficient radical formation and LSPR-induced heat generation, with cancer cell death primarily following an apoptotic pathway. In vivo animal studies further confirm the tumor suppression ability of Au NR@aTiO2@UCNPs through combinatorial photothermal and photodynamic effect. Our hybrid nanomaterials emerge as excellent multifunctional phototherapy agents, providing a valuable addition to light-triggered cancer treatments in deep tissue.

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.

Because the particle shape, size, and spacing in SiCp/Al composites are not constant, the stochastic fluctuation phenomenon of their cutting force is more remarkable than those of continuous materials. This study aims to develop an analytical model of the dynamic cutting force in the orthogonal cutting of SiCp/Al composites. The stochastic models of the particle volume fraction, particle size, and aspect ratio are established. Based on analysing the mechanical mechanisms in different zones and the heat generation mechanisms in the shear and rubbing sources in the cutting process, a dynamic cutting force model is developed for SiCp/Al composites. This model considers the stochasticity of the particle characteristics and the dynamic change characteristic of heat generation. The predicted results yielded the average and maximum relative errors for the tangential force as 7.29% and 9.86%, respectively, and those for the radial force as 7.36% and 10.33%, respectively. Comparison of the analytical and experimental results presents a good agreement. The effects of the cutting parameters and the tool wear on the average cutting force in the orthogonal cutting of SiCp/Al composites are discussed. Moreover, the effects of the particle characteristics on each component of the cutting force are also analysed. In particular, the dynamic cutting force model can accurately present the dynamic fluctuation characteristics of the cutting process of SiCp/Al composites and study the variation tendency of average cutting force. This work provokes more in-depth thoughts of dynamic fluctuation details in the cutting process and provides the guiding significance for industrial SiCp/Al composites machining.

Heat generation in integrated circuits (ICs) has become a severe issue, which limits the utilization of miniaturized semiconductor devices in high-density 3-D IC technologies. Herein, Al₂O₃ was doped in ZrO₂ thin films by plasma-enhanced atomic layer deposition (PEALD) to enhance their antiferroelectric (AFE) characteristics for highly reliable electrocaloric (EC) cooling applications. The cycling endurance in AFE behaviors of the Al:ZrO₂ thin films under a high electric field of 5 MV/cm was significantly improved because of the enlargement of the energy bandgap with high resistance in trap-induced leakage current. Hence, the reliability of the EC effect of the 1% Al:ZrO₂ thin film was examined with a negligible change in adiabatic temperature change (Δ T) of 2.6% after a cycling endurance test of 10⁶ cycles. With the competitive cycling reliabilities in AFE and EC behaviors, devices with optimized Al₂O₃-incorporated ZrO₂ thin films show significant potential for future nanoscale cooling systems in chip-level ICs.

Recently, a polygonal boundary element method (PBEM) has been developed for solving heat conduction problems. In the PBEM, the radial integration method (RIM) is employed to shift the domain and surface integrals in the boundary-domain integral equation into equivalent line integrals, and all the radial integrals are computed by Gaussian quadrature, which may obtain an accurate solution. However, the computation costs much. Therefore, analytical expressions of radial integrals are derived in this paper, concerning four kinds of varying thermal conductivities and two kinds of heat generation functions, aiming at improving the efficiency. Then all the radial integrals in the boundary-domain integral equation can be analytically calculated. Three examples are employed to examine the analytically-integrated PBEM for solving steady heat conduction problems. The results show that the proposed method is accurate, and it is more efficient than traditional PBEM.

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.

With the rapid development of manufacturing industry, the application of motorized spindle is more and more widely, which puts forward higher requirements for the accuracy and failure rate of motorized spindle. However, a large amount of heat will be generated in the working process, which makes the performance of motorized spindle difficult to meet the requirements, so the thermal properties of motorized spindle need to be further studied to make the dynamic behavior better. In this research, first, the characteristics of inner/outer ring curvature radius and oil film thickness were considered in the mechanical analysis of bearing. Second, a new bearing force equilibrium model including the factors of centrifugal force, gyro moment, and ring expansion was established, in which the deformation caused by centrifugal and thermal effect was separated from the deformation caused by Hertz contact, and then the force-displacement analysis was performed. Third, the heat generation and heat transfer of motorized spindle were fully analyzed and detailed based on the thermal network method, and an optimized convective heat dissipation model for bearings was proposed. In addition, the influence of the oil film thickness on the bearing displacement model was discussed. Next, Newton-Raphson method was employed to calculate the motorized spindle network model and the temperature distribution was obtained. Finally, the temperature rise test of motorized spindle was implemented with variable parameters. And the test data were analyzed and compared with the theoretical results, which indicates that thermal network model established in this investigation has a good validity and reliability.

The impact of variable fluid properties (viscosity and thermal conductivity) and magnetic dipole on biomagnetic Maxwell fluid past a stretching sheet with slip velocity and heat generation/absorptionhave been studied. Similarity transformation technique is adopted to obtain the self-similar coupled nonlinear ordinary differential equations. Using similarity variable, the basic governing equations with boundary conditions are transformed and solved in bvp4c technique with MATLAB software. The contribution of different pertinent parameters such as viscosity, thermal conductivity and ferromagnetic parameter on the flow profiles with physical quantities are analyzed and examined through graphically. Results shown that with increasing ferromagnetic parameter, slip parameter, Maxwell parameter, velocity decreases but temperature increases. For accuracy of the proposed model to compare our numerical results in numerically and graphically with the previousliterature under some limiting cases and a good agreement is found. Dhaka Univ. J. Sci. 69(2): 109-115, 2021 (July)

The thermal resistance of a high electron mobility transistor (HEMT) forming part of a monolithic microwave integrated circuit (MMIC) is noninvasively extracted under real working conditions (electrical and thermal) by infrared thermal imaging. The HEMT thermal resistance considers the device local maximum temperature and dissipated power. An experimental approach to this end is currently not available, as the HEMTs thermal interaction does not allow extracting its individual heat generation. Thanks to thermal field confinement offered by heat source frequency modulation, the power dissipation in each device is inferred, making feasible its individual thermal resistance extraction. As a result, reasonable values of the local thermal resistance of each individual HEMT integrated in the MMIC (i.e., 57.8 ± 3.4 °C/W and 24.8 ± 1.4 °C/W) are obtained in agreement with studies on discrete devices available in the literature.

The knowledge of cutting forces in various machining processes is of great importance not only for the designer-manufacturer of machine tools, but also for the user, since the cutting force governs cutting heat generation, tool life, and machining accuracy. In this regard, lots of investigations have been conducted on the cutting forces by developing different types of prediction models to make appropriate estimations, which are grouped into the analytical, empirical, and numerical methods. This paper conducts a survey on the development of analytical cutting force models for the orthogonal turning/cutting process. The analytical force models developed from the shear theory are detailed reviewed, and other analytical modeling methods for specially-designed tools, advanced materials, and special kinematics are also presented. The modeling laws and key challenges are also discussed for future researches.

Li metal batteries with high-capacity cathodes emerge as promising candidates for next-generation battery technologies. However, the poor reversibility of the Li deposition/stripping process severely reduces its lifespan, and safety also remains a major issue for the Li metal anodes. Herein, we propose (ethoxy)-penta-fluoro-cyclo-triphosphazene (DFA) as a dual-functional electrolyte additive to solve the engineering problem of balancing the cycle life and thermal stability of Li metal batteries. The NCM811/lithium metal pouch batteries (2900 mA h) are assembled using the commercial high areal capacity cathode (3.5 mA h cm-2). Compared with the NCM811/Li batteries without DFA, the heat generation and heat generation power of lithium metal batteries with DFA are significantly reduced by half during charging. Moreover, the NCM811/Li pouch batteries with DFA show excellent stability in both hot-oven and adiabatic rate calorimeter experiments. Furthermore, a nonlinear phase field simulation is carried out for mechanism investigation, which confirms that the stable solid electrolyte interphase formed by DFA will improve the cycle life of the NCM811/Li pouch. The DFA is verified to be an effective additive to improve the cycle stability and safety simultaneously, providing new opportunities for developing high energy density Li metal batteries.

© 2021 Wiley Periodicals LLC.Implantable thermo-responsive drug-loaded magnetic nanofibers (NFs) have attracted great interest for localized thermo-chemotherapy of cancer tissue/cells. From this perspective, smart polymeric electrospun NFs co-loaded with magnetic nanoparticles (MNPs) and a natural polyphenol anticancer agent, curcumin (CUR), were developed to enhance the local hyperthermic chemotherapy against melanoma, the most serious type of skin cancer. CUR/MNPs-loaded thermo-sensitive electrospun NFs exhibited alternating magnetic field (AMF)-responsive heat generation and “ON–OFF” switchable heating capability. Besides, corresponding to the reversible alterations in the swelling ratio, the “ON–OFF” switchable discharge of CUR from the magnetic NFs was detected in response to the “ON–OFF” switching of AMF application. Due to the combinatorial effect of hyperthermia and release of CUR after applying an AMF (“ON” state) for 600 s on the second and third days of incubation time, the viability of the B16F10 melanoma cancer cells exposed to the CUR/MNPs-NFs was reduced by 40% and 17%, respectively. Taken together, the macroscopic and nanoscale features of the smart NFs led to the creation of a reversibly adjustable structure that enabled hyperthermia and facile switchable release of CUR for eradication of melanoma cancer cells.

In this study, the plane thermoelastic frictional contact problem between a magneto-electro-elastic (MEE) layer and a rigid cylindrical or flat punch is discussed. Punches are assumed to be perfect...

Lithium-ion batteries have been widely used in the power-driven system and energy storage system, while overcharge safety for high-capacity and high-power lithium-ion batteries has been constantly concerned all over the world due to the thermal runaway problems by overcharge occurred in recent years. Therefore, it is very important to study the thermal runaway mechanism and improve the safety of the battery during overcharge. In this work, depending on the external appearance, voltage, and temperature changes, the whole overcharge to TR process was divided into 5 stages. By analyzing the side reactions in five stages, the mechanism of heat production during overcharge is summarized, and the order of heat generation is QCa+An > Qanode > Qelectrolyte > Qcathode > QSEI > QISC. Key factors for battery overcharge safety, such as cathode materials, electrolyte safety, and charging current are concluded in this review. Compared to external protection devices (such as BMS, OSD, CID), the internal protection of overcharge additives are more effective. A complex polymer with aromatic functional groups, epoxy or propionate, will become a hot spot in the research of overcharge additives for lithium-ion batteries. This review is expected to offer effective overcharge safety strategies and promote the development of lithium-ion battery with high-energy density.