Amount Of Heat Generation Research Articles

Heat transfer analyses in friction stir welding of aluminium alloy

This work is aimed to develop a heat transfer model of friction stir welding process and subsequently to utilize the same for transient thermal analysis under differential influence of process parameters. The heat generation is assumed due to friction and plastic deformation at the tool–workpiece interface. A contact state variable is defined to estimate the amount of heat generation due to plastic deformation. The symmetric heat flux at the interfaces of flat tool shoulder surface, tool pin side, and bottom surfaces acts as heat input to the system by neglecting the effect of transverse tool speed. The heat generation from both the side and bottom surfaces of pin plays a significant role for the development of the temperature. Thermal history of friction stir welded AA1100 and AA6061 is estimated by developed numerical model and is compared with experimental results under similar welding conditions, thus validating the developed model. The experiments reveal that the temperature distributions are not symmetric with respect to welding line and maximum temperature occurs behind the tool pin. With the addition of heat generation due to plastic deformation, the heat transfer model precisely predicts the maximum temperature and time–temperature profiles at different welding conditions.

10309 ソーラーパネルを裏面から冷却による温度低下の数値解析

The solar panel is heated by energy of radiation from the sun. The efficiency of electric transduction of solar panel is decreased with increasing temperature. Therefore, this paper described that the effect of cooling by natural re-circulation flow of solar panel temperature using two-dimensional numerical analysis. This numerical analysis was used OpenFOAM code based on PMPLE method. The solar panel was assumed the heating plate with the heat source. The inclination angle of the heating plate was 30 degrees, and the analyses were carried out by changing the ambient air temperature, the cooling water temperature and the amount of heat generation at heating plate. Results show that the temperature of the heating plate is decreased by cooling water and ambient air temperatures. This mechanism and relations are also discussed.

Determination of tool friction in presence of flank wear and stress distribution based validation using finite element simulations in machining of titanium and nickel based alloys

Tool friction plays a very important role in machining titanium and nickel-based alloys and is an important parameter in Finite Element based machining simulations. It is the source for the high amount of heat generation, and as a result, the excessive flank wear during machining these materials. The worn tool is known to create poor surface qualities with high tensile surface residual stresses, machining induced surface hardening, and undesirable surface roughness. It is essential to develop a methodology to determine how and to what extent the friction is built up on the tool. This study facilitates a determination methodology to estimate the stress distributions on the rake and flank surfaces of the tool and resultant friction coefficients between the tool and the chip on tool rake face, and the tool and the workpiece on tool flank face. The methodology is applied to various tool edge radii and also utilized in solving stagnation point location on the tool edge. Predicted friction results are further validated with comparison of predicted stress distributions from FE simulations for machining of titanium alloy Ti-6Al-4V and the nickel-based alloy IN-100. It was found that tool stresses and friction are mainly influenced by tool rake angle, edge radius, and tool flank wear and are slightly affected by the cutting conditions in the ranges that were considered in this study.

A New Type of Protective Surface Layer for High-Capacity Ni-Based Cathode Materials: Nanoscaled Surface Pillaring Layer

A solid solution series of lithium nickel metal oxides, Li[Ni(1-x)M(x)]O2 (with M = Co, Mn, and Al) have been investigated intensively to enhance the inherent structural instability of LiNiO2. However, when a voltage range of Ni-based cathode materials was increased up to >4.5 V, phase transitions occurring above 4.3 V resulted in accelerated formation of the trigonal phase (P3m1) and NiO phases, leading to and pulverization of the cathode during cycling at 60 °C. In an attempt to overcome these problems, LiNi0.62Co0.14Mn0.24O2 cathode material with pillar layers in which Ni(2+) ions were resided in Li slabs near the surface having a thickness of ∼10 nm was prepared using a polyvinylpyrrolidone (PVP) functionalized Mn precursor coating on Ni0.7Co0.15Mn0.15(OH)2. We confirmed the formation of a pillar layer via various analysis methods (XPS, HRTEM, and STEM). This material showed excellent structural stability due to a pillar layer, corresponding to 85% capacity retention between 3.0 and 4.5 V at 60 °C after 100 cycles. In addition, the amount of heat generation was decreased by 40%, compared to LiNi0.70Co0.15Mn0.15O2.

Experimental study of a cavitation heat generator

Recent research has investigated the use of ultrasonic or hydrodynamic cavitation for chemical reactors, water treatment equipment, and heat generators. In this article, a new cavitation heat generator is introduced. The proposed system utilizes an electric motor to rotate the generator, and various experiments are performed by changing the flow conditions such as inlet pressure and rotating velocity to evaluate the performance of it. In addition, the amount of heat generation is measured and the thermal efficiency is evaluated. The result is a highly efficient heat generator that can reach 90% thermal efficiency.

Optical Spectroscopic Analysis of Muscle Spasticity for Low-Level Laser Therapy (LLLT)

Current therapeutic methods for suppressing muscle spasticity are intensive functional training, surgery, or pharmacological interventions. However, these methods have not been fully supported by confirmed efficacy due to the aggravation of the muscle spasticity in some patients. In this study, a combined system was developed to treat with a low-level laser and to monitor the region of the treatment using an optical spectroscopic probe that measures oxygen saturation and deoxygenation during low-level laser therapy (LLLT). The evaluation of the wavelength dependence for LLLT was performed using a Monte Carlo simulation and the results showed that the greatest amount of heat generation was seen in the deep tissue at <TEX>${\lambda}$</TEX> = 830 nm. In the oxy- and deoxygenation measurements during and after the treatment, oxygen-Hb concentration was significantly increased in the laser-irradiated group when compared to the control group. These findings suggest that LLLT using <TEX>${\lambda}$</TEX> = 830 nm may be of benefit in accelerating recovery of muscle spasticity. The combined system that we have developed can monitor the physiological condition of muscle spasticity during the laser treatment in real time and may also be applied to various myotonia conditions such as muscle fatigue, back-pain treatment/monitoring, and ulcer due to paralysis.

Improved Rate Capability and Thermal Stability of LiNi0.5Co0.2Mn0.3O2 Cathode Materials via Nanoscale SiP2O7 Coating

LiδPyOz–coated LiNi0.5Co0.2Mn0.3O2 cathode materials doped with P and Si ions were prepared by direction reaction of LiOH and SiP2O7-coated Ni0.5Co0.2Mn0.3(OH)2 precursors. The coated cathodes exhibited quite impressive results; rate capability was improved by almost 100% at a 7 C rate compared to pristine LiNi0.5Co0.2Mn0.3O2. Furthermore, the amount of heat generation at 4.5 V charge cut-off as a result of the evolution of oxygen was reduced by 79%, compared to pristine LiNi0.5Co0.2Mn0.3O2 sample.

Effects of Silica Fume on Heat Generation of Curing Concrete

During the curing of concrete heat is generated from the chemical reactions in the concrete mixture. As heat accumulates within the concrete mass a substantial rise in temperature occurs. The heat dissipation through the concrete surface causes nonuniform temperature distribution leading to an uneven thermal expansion and contraction of the concrete mass. Internal restraint due to temperature difference within the concrete mass and external restraint due to rigid connections to movement restraints often induce tensile strains that are large enough to cause early thermal cracking. Currently, silica fume (SF) is quite commonly used for the production of high-performance concrete. The effects of SF on heat generation of curing concrete, however—especially in the presence of other pozzolanic materials such as fly ash (FA) and at different water-cementitious material ratios (w/cm)—are still not clearly known. To study the combined effects of SF and FA at different w/cm, concrete mixtures with SF replacement up to 10% are presented, FA replacement up to 20%, and w/cm ranging from 0.24 to 0.40 were produced for semi-adiabatic curing tests. Heat loss compensation was applied to determine the adiabatic temperature rises of the concrete mixtures. The test results revealed that (1) the heat generation per weight of cementitious materials is generally smaller at a lower w/cm; (2) within the range of parameters studied, SF replacement would reduce the amount of heat generation but increase the rate of heat generation; and (3) compared on an equal strength basis, 5 and 10% SF replacement would reduce the amount of heat generation by approximately 10% and 20%, respectively.

Ductile Fracture Prediction in Rotational Incremental Forming for Magnesium Alloy Sheets Using Combined Kinematic/Isotropic Hardening Model

To predict the ductile fracture of a magnesium alloy sheet when using rotational incremental forming, a combined kinematic and isotropic hardening law is implemented and evaluated from the histories of the ductile fracture value (I) using a finite element analysis. Here, the criterion for a ductile fracture, as developed by Oyane (J. Mech. Work. Technol., 1980, vol. 4, pp. 65–81), is applied via a user material based on a finite element analysis. To simulate the effect of the large amount of heat generation at elements in the contact area due to the friction energy of the rotational tool-specimen interface on the equivalent stress-strain evolution in incremental forming, the Johnson–Cook (JC) model was applied and the results compared with equivalent stress-strain curves obtained from tensile tests at elevated temperatures. The finite element (FE) simulation results for a ductile fracture were compared with the experimental results for a (80 mm × 80 mm × 25 mm) square shape with a 45 and 60 deg wall angle, respectively, and a (80 mm × 80 mm × 20 mm) square shape with a 70 deg wall angle. The trends of the FE simulation results agreed quite well with the experimental results. Finally, the effects of the process parameters, i.e., the tool down-step and tool radius, on the ductile fracture value and FLC at fracture (FLCF) were also investigated using the FE simulation results.

Entropy generation in a square cavity

Purpose – The purpose of this paper is to study flow over two heat generating porous blocks situated in a cavity, and examine the effects of porous blocks geometric orientations in the cavity (configurations) and the amount of heat generation in the blocks on entropy generation rate due to heat transfer and fluid flow.Design/methodology/approach – Four configurations of blocks and three heat fluxes are accommodated in the simulations. The equilibrium flow equations are used to compute the flow field. Entropy generation in the flow system due to fluid friction and heat transfer is also computed. A control volume approach is used to discretize the governing equations of flow and heat transfer. In the simulations, flow Reynolds number is kept 100 at cavity inlet and blocks' porosity is set to 0.9726.Findings – The volumetric entropy generation rate attains high values around the blocks and configuration 4 results in reasonably low values of entropy generation rate due to heat transfer and fluid flow.Research...

Combined kinematic/isotropic hardening behavior study for magnesium alloy sheets to predict ductile fracture of rotational incremental forming

In order to predict the ductile fracture of rotational incremental forming for magnesium alloy sheet , a combination of kinematic and isotropic hardening law is implemented and ev aluated from the histories of ductile fracture value (I) by means of finite element analysis. Here, the criterion for a ductile fracture, as developed by OYANE, [J. Mech. Work. Tech. 4 (1980), pp. 65-81], is carried out via a user material, using finite el ement code. To simulate the effect of the large amount of heat generation at elements in the contact area due to friction energy of the rotational toolspecimen interface on equivalent stress-strain evolution in incremental forming, Johnson -Cook model was applied and also compared with equivalent stress -strain curves obtained by tensile test at elevated temperatures. The FE simulation results of ductile fracture was then compared with the experimental results of 80 mm × 80 mm × 25 mm square shape with 45°, 60°, and 80 mm × 80 mm × 20 mm square shape with 70° wall angles. The trend of FE simulation results were quite in good agreement with experiment results. Finally, the effect of process parameters e. g tool down -step and tool radius on the ductile fracture value and forming limit curve at fracture (F LCF) were investigated using FE simulation results

A Comparison of Wavelength Dependence for Laser-assisted Lipolysis Effect Using Monte Carlo Simulation

The aim of this study is to evaluate wavelength dependence for laser-assisted lipolysis using a mathematical simulation. In this study, a Monte Carlo simulation was performed to simulate light transport in fat and dermal tissue with 3 different laser wavelengths (<TEX>${\lambda}\;=\;1064\;nm$</TEX>, 1320 nm, and 1444 nm) that are currently used in clinic settings for laser-assisted lipolysis. The relative rates of heat generation versus penetration depth showed that the greatest amount of heat generation was seen in the tissues at <TEX>${\lambda}\;=\;1444\;nm$</TEX>. This Monte Carlo simulation may help lend insight into the thermal events occurring inside the fat and dermal tissue during laser-assisted lipolysis.

Analysis of thermal and electrical properties of ZnO arrester block

Voltage–current characteristics of ZnO surge arresters are highly dependent on temperature in the low-conduction region. ZnO surge arresters experience thermal runaway when the temperature exceeds the acceptable limit. This phenomenon is associated with the increase of resistive leakage current due to degradation. This paper presents the thermal and electrical characteristics of ZnO arrester blocks under the power frequency AC operating voltages. The leakage currents of ZnO arrester blocks were measured over a period of the time. The temperature profiles of ZnO arrester blocks were observed by the infrared camera. The degradation and the thermal runaway of the ZnO arrester blocks are closely related to the temperature limit which determines the heat generation and dissipation. As the leakage current was 0.5 mA, the amount of heat generation is lower than that of heat dissipation. So temperature of the ZnO arrester blocks was rarely changed. On the other hand, as the leakage current was 0.7 and 1 mA, the amount of heat generation was greater than that of the heat dissipation. The temperature of ZnO arrester blocks gradually increases and the test specimen experiences thermal runaway. At that time the temperature located at the center of ZnO arrester blocks string was higher compared to that of ZnO block at both edges.

Thermal and magnetic behaviors of a melt-textured superconducting bulk magnet in thezero-field-cooling magnetizing process

The heat generation and magnetic field trapping behaviors of the melt-texturedsingle-domain Sm–Ba–Cu–O bulk superconductor have been precisely investigated in thezero-field-cooling magnetizing processes (ZFC). The temperature and magnetic flux densitywere simultaneously measured in the temperature range of 50–60 K. Since the invasion ofmagnetic flux is suppressed by the superconducting pinning effect, the applied magneticfield is not supplied to the whole of the sample. Therefore, the trapped field distributionsconsequently exhibit trapezoid shapes. According to the balance of heat generation anddraining, the temperature profiles show us distinctive behaviors of magnetic fluxes. Boththe temperature and the magnetic flux density kept increasing even after the externalmagnetic field has stopped growing at 5 T. This is attributed to the flux creepingphenomenon which propagates from the periphery to the center portion of thesample like a snow slide. The highest temperature rise due to the flux motionreached 7.5 K even when the sample was magnetized at a slow sweeping rate of 5.06 mT s−1. As the temperature profiles were different between the ascending and descending fieldprocesses, it is suggested that the magnetic fluxes invade in and diffuse out in differentheating manners between the processes. This assists the hypothesis that the timewhile the moving fluxes heat the sample strongly affects the total amount ofheat generation, which acts contrary to the FC case. This behavior implies thatthe improvements of the heat propagation property of the HTS bulk materialby embedding metallic membranes and more powerful/efficient cooling systemsmust suppress the temperature increases and enhance the field trapping abilities.

Thermo-electro-mechanical Performance of Piezoelectric Stack Actuators for Fuel Injector Applications

Piezoelectric actuators are increasingly used in fuel injectors due to their quick response, high efficiency, accuracy, and excellent repeatability. Current understanding of their thermo-electro-mechanical performance under dynamic driving conditions appropriate for fuel injection is, however, limited. In this paper, the thermo-electro-mechanical performance of soft Lead Zirconate Titanate (PZT) stack actuators is experimentally investigated over a temperature range of -30°C to 80°C, under driving electric fields of up to 2.0 kV/mm (using an AC drive method and a biased DC offset), different frequencies, and a constant preload of about 5 MPa. Experimental results show that the dynamic stroke of the actuators increases with the magnitude and frequency of the applied electric field, as well as ambient temperature. The dynamic stroke was also found to increase with decreased driving field rise time, which is equivalent to increasing the driving field frequency. At driving frequencies lower than the resonance frequency of the test apparatus (~500 Hz), the strain-electric field behavior under different temperatures agreed well with previously obtained quasi-static results. The duty cycle was found to have a minimal effect on dynamic stroke but significantly affected the amount of heat generated under high electric field magnitudes and/or frequencies. The temperature increase due to self-heat generation under a continuous AC driving field (100% duty cycle) was very high, and limited the maximum driving field magnitude and/or frequency. Reducing the duty cycle significantly decreased the amount of heat generation.

Investigation of the kinetic mechanism in overcharge process for Li-ion battery

Commercial Li-ion batteries have been submitted to different stage of overcharge by a “soft” overcharging technique. This technique gives us flexibility to investigate each step of the overcharging process. DSC and SEM tests of the anode, cathode and separator recovered from overcharged cells have been performed. It was shown that the thermal runaway will happen when the heat generation is not equal to the heat dissipation during the battery operated at an overcharge condition. The high overcharging rate shows short responding time for the cell thermal runaway and large amount of heat generation. A kinetic mechanism proposed in this study for interpreting the observation of species growth on the surface of separator in the anode side and causing soft shorting of the cell.

Characterization of cooling heat transfer for various coolant conditions in warm forging process

Because of the elevated temperatures in the warm or hot forging processes, the temperature of tools plays a major role in their service life. To increase tool life in warm or hot forging processes, forging conditions such as lubricants, cooling methods, tool material, heat treatment of tools and workpiece temperature should be optimized. All of these conditions are closely related to the temperature of active tools, so it is difficult to determine which factors are dominant and which ones require an accurate prediction of temperature changes in order to be changed. In warm or hot forging processes, the amount of heat generation by plastic deformation, heat transfer between workpiece and tools and the coolant cooling rate are essential for predicting the exact temperature of the workpiece and active tools. In this research, to determine the convective heat transfer coefficient with respect to different lubricants, the temperature of surface and lubricant was measured using flowing cooling experiments for the heat treated tools made of H13 steel. The convective heat transfer coefficients were calculated using both the measured temperature and inverse method algorithm. The calculations were performed using MPL code, which was developed for thermo-mechanical plastic deformation analysis. The calculated convective heat transfer coefficient was used in finite element analysis and verified.

Thermal hydraulics of the spallation target module of an accelerator driven sub-critical system: A numerical study

The mechanical design of the target module of an accelerator driven sub-critical nuclear reactor system (ADSS) calls for an analysis of the related thermal–hydraulic issues because of the sheer large amount of heat generation in its spallation target system during the course of nuclear interactions with the molten lead bismuth eutectic (LBE) target. The window of the target module is subject to high heat fluxes due to the direct impingement of high energy proton beam on its surface. A large amount of heat is deposited on the window and in the bulk of the LBE in the spallation region. Therefore, the problem of heat removal by the LBE is a challenging thermal–hydraulic issue. For this, one will need to examine the laminar/turbulent flows of low Prandtl number fluids (LBE) in a complex target module of an ADSS. In this study, the equations governing the flow and thermal energy are solved numerically using the streamline upwind Petrov–Galerkin (SUPG) finite element (FE) method. Special consideration has been given to the window under various thermal conditions, such as, isothermal, uniform and variable heat flux. The analysis has been extended to the case of heat generation in the liquid LBE. The principal purpose of the analysis is to trace the temperature distribution on the beam window and in the LBE. This also helps to check the suitability of the geometry in avoiding the recirculation or stagnation zones in the flow space that may lead to hot spots.

Heat generation and heat transfer in cylindrical grinding process -a numerical study

Grinding is the most common abrasive machining process and in many cases the last of the series of machining operations. Compared to other machining processes grinding requires very high-energy input per unit of volume of material removal. The chip removal process consists of rubbing, plowing and metal removal. The frictional resistance encountered between work material, the tool, and the chip tool interface and the resistance to deformation during shearing of chips contributes to a rise in temperature and the cutting zone. The temperature generated is not only quite high but the temperature gradients are also severe. Under abusive grinding conditions, the formation of the heat-affected zone was observed which damages the ground surfaces of the workpieces. The present work aims at optimizing the amount of heat generation and modeling the temperature rise between wheel and work contact zone in a cylindrical grinding process so as to achieve better surface integrity in AISI 3310, AISI 6150, and AISI 52100 steel materials. Taguchi’s methodology a powerful tool in design of experiments for quality is used for optimization process.

회전노즐장비 작동시 하수관내의 열전달 및 유동현상에 관한 연구

Heat transfer and flow characteristics in a pipe in which the rotating cutting tool for boring a underground pipe without digging were considered in this study. The amount of heat generation due to the friction between the rotating cutter and pipe wall, mixing (low of air and water injected to cool down are the two important factors to design the boring machine Computational fluid dynamics analysis using the Eulerian mixture model and the standard turbulence model was used to analyze the complex phenomena in a pipe during the process. Results show that pipe wall temperature decreased with increasing the cooling water inlet velocity. it is also shown that pipe wail temperature was lowered when the cutter rotation speed was increased until 600 rpm. There was no further cooling effect over 600 rpm.