Heat Generation Characteristics Research Articles

Analysis of heat generation characteristics in ultrasonic welding of plastics under low amplitude conditions

Abstract Heat generation mechanism in processes of ultrasonic welding of plastics was not fully solved. Experiment results showed that increasing the amplitude increased the energy dissipated with the exception of low amplitudes, but no detailed analysis can be found in explaining this problem. This study proposed to investigate the heat-generating processes in such a condition with a new physically based model by solving the N-S equations. The increasing mean temperature profiles and the final temperature patterns are well agreed with previous researches. The results predicted that the distribution of heat generated in the welding zone was non-uniform. The highest temperature area changed its position with the variation of time and the amplitude of vibration. In low amplitude conditions, energy dissipation was found to firstly increase with a slight fluctuation, then decreased when the driven amplitude was larger than 5 μm. And different temperature distribution patterns were observed at these turning points.

Investigation into effect of thermal expansion on thermally induced error of ball screw feed drive system of precision machine tools

In order to investigate the effect of thermal expansion on the ball screw feed drive system of a precision boring machine tool, theoretical modeling of and experimental study on thermally induced error along with heat generation characteristics are focused in this paper. A series of thermal experiments are conducted on the machine tool to measure and collect the thermodynamic data with the feed drive system operating at different speeds. Based on the heat generation and transfer analysis of ball screw system, thermal expansion of screw shaft in the axial direction is modeled mathematically. Relationships between the thermal error and axial elongation are established to characterize the thermal error distribution considering the thermal expansion coefficient as a temperature-variant parameter. It turns out that the thermal error varies with different working positions through the ball screw length and working time nonlinearly, and there definitely exists certain transform from the thermal expansion to the thermal error obtained by measurement. In addition, regression analysis is employed to carry out the theoretical modeling of thermal error with the temperature data of the critical heat generation points. The relations between temperature rise and thermal error are formulated directly while taking the thermal expansion as an implicit variable. Experiments under a different condition are preformed and the proposed methods for thermal error modeling prove to be effective and accurate enough to be used in the machining process as well.

Experiment-based thermal error modeling method for dual ball screw feed system of precision machine tool

In order to investigate the thermal behavior of a dual ball screw feed drive system of a precision boring machine tool, experimental study on and theoretical modeling of thermally induced error along with heat generation characteristics are conducted in this paper. Experiments are carried out on the machine tool to measure and collect the thermodynamic information with its feed drive system operating under different working conditions. Based on the real-time data of the thermal expansion of ball screw in the axial direction, relationships between the thermal error and axial elongation are established to predict the thermal error distribution. The results show that the thermal error varies with different working position through the ball screw length linearly and with working time nonlinearly. In addition, another simplified way to model thermal error is presented to overcome the difficulties existing in the ball screw feed drive system of which the axial elongation is hard to collect. Fuzzy clustering and linear regression methods are employed to carry out the theoretical modeling of thermal error and optimization to sift out the critical heat sources. With the temperature data of these critical heat generation points, the thermally induced error of the ball screw feed drive system can be predicted easily alternatively. Experiments under a different condition are preformed to verify both prediction and modeling methods. It turns out that the proposed prediction methods are effective and practical to be used in the machining process as well.

Theoretical and experimental investigation on the thermal characteristics of double-row tapered roller bearings of high speed locomotive

Thermal characteristics critically affect the service reliability of double-row tapered roller bearing in high speed railway. Research on the heat generation and temperature field is essential for bearing’s structure design and operation monitoring. In this article, heat generation model for both raceway and rib of railway bearings were respectively established via the combination of local thermal approach with elastohydrodynamic lubrication (EHL) theory, the heat generation characteristics of bearing were investigated in multiple working conditions and structural parameters. Then the finite element method was employed via the APDL program to analyze bearing’s temperature field distribution and its influence factors. The test rig for full-size double-row tapered roller bearing of high speed railway was constructed and the thermal monitoring were conducted in accordance with the test criteria TB/T3000-2000, the thermal test method on the axle-box test rig for axle-box rolling bearings in rolling stock. The results showed that, for the total heat rate of each column rollers, heat generation of the raceway was much larger than the other parts, which would have distinct effect on bearing’s overall temperature. For the heat rate per unit area, heat generation of the rib was much obvious. Hence it would be a key factor to induce the local transient temperature rise of high speed railway bearing. The highest temperature of inner ring was located in the rib. Therefore the rib would be a critical part for the temperature rise failure of high speed railway bearing. Optimization of the rib parameters will be an effective approach for controlling the local temperature rise and ensuring the reliability during bearing operation.

Heat generation characteristics of microheaters prepared with ITO nanoparticles and organic additives

In this study, we demonstrate the heat generation characteristics of microheaters prepared with an ITO nanoparticle (NP) paste, which is a mixture of ITO NPs, polymethyl methacrylate, and terpineol. A comparison with microheaters prepared with ITO NPs only shows that the organic additives substantially enhance their heat generation characteristics. The maximal temperature obtained is 445°C at a bias voltage of 12V, which is three times higher than for the NP microheaters. Moreover, the NP-paste microheaters have better thermal stability and a more uniform heating zone. The enhancement in the heat generation characteristics results from the smoother surfaces and the higher density of the NP-paste films.

Effect of humidified water vapor on heat balance management in a proton exchange membrane fuel cell stack

Summary Thermal management has been considered as one of the most important issues for the operation of proton exchange membrane fuel cells (PEMFCs). Phase change affects the performance and even the heat balance of the stack during operation. A 46 single cell PEM stack with anode and cathode humidification is developed to investigate, both theoretically and experimentally, the effect of phase change on the heat generation and removal characteristics of the stack. The results show that the heat removed by the coolant water is greater than that generated by the electrochemistry reaction, and heat released due to the phase change of water vapor cannot be neglected. Heat generated in the stack can be removed completely by the coolant water, which need to be forced cooling for recycling use when the current density reaches 1000 mA·cm−2. The arithmetic product of the specific heat capacity and mass of the stack can be used as a novel criterion to evaluate the validity of the heat balance in the system. The exothermic reaction is very fast in the stack, which consequently requires bipolar plates with high heat conductivity coefficient to improve the temperature uniformity at the elevated operational current density. Copyright © 2014 John Wiley & Sons, Ltd.

Measurements of heat generation in prismatic Li-ion batteries

An accurate understanding of the characteristics of battery heat generation is essential to the development and success of thermal management systems for electric vehicles. In this study, a calorimeter capable of measuring the heat generation rates of a prismatic battery is developed and verified by using a controllable electric heater. The heat generation rates of a prismatic A123 LiFePO4 battery is measured for discharge rates ranging from 0.25C to 3C and operating temperature ranging from −10 °C to 40 °C. At low rates of discharge the heat generation is not significant, even becoming endothermic at the battery operating temperatures of 30 °C and 40 °C. Heat of mixing is observed to be a non-negligible component of total heat generation at discharge rates as low as 0.25C for all tested battery operating temperatures. A double plateau in battery discharge curve is observed for operating temperatures of 30 °C and 40 °C. The developed experimental facility can be used for the characterization of heat generation for any prismatic battery, regardless of chemistries.

Heat Generation Characteristics and Heat Dissipation Experiment of CPU Chip

With the development of the CPU integration, providing effective heat removal solutions for chip is an important research. This article analyses the reason of chip overheat and different adopted techniques in chip heat dissipation and commits itself to take the variation of the operating conditions into account to obtain the overall temperature rising curve based on a simplified thermal model. And then it utilizes heating plate as constant heat source to simulate CPU heating. Under the power of 20W, 30W and 40W, we compare five kinds of fan-cooled radiators in order to provide the experimental statistics for the further design and theoretical analysis.

철손밀도 분포에 의한 열원이 고려된 3차원 열등가회로망을 이용한 경량전철 구동용 110kW급 IPMSM의 열 특성 연구

A research on thermal analysis method is conducted for the characterization of heat generation during operation of Interior Permanent Magnet Synchronous Motor(IPMSM) for Light Railway Transits(LRT) in this paper. Efficient cooling of the heat generated in the IPMSM is important because the excessive heat generated from the winding, core and permanent magnet makes it harder for a long time continuous operation of IPMSM. Therefore, in order to analyze the heat generation characteristics of the 110kW-class IPMSM as advanced research for application the IPMSM to the cooling device, the heat transfer coefficients for each component of the 110 kW-class IPMSM were derived and the thermal equivalent network was configured to perform the thermal analysis in this study. Finally, theBR110kW-class IPMSM prototype is made and a comparative verification between the test data and the thermal analysis results through its various performance tests are carried out.

철도차량용 영구자석 동기전동기의 열해석 기법 연구

본 논문에서는 철도차량 추진용 매입형 영구자석 동기전동기(Interior Permanent Magnet Synchronous Motor, IPMSM)의 운전 중 열 발생 특성 분석을 위한 열해석 기법 연구를 수행하였다. IPMSM의 구동 중에 권선, 코어, 영구자석에서 발생되는 과도한 열은 IPMSM의 장시간 연속운전을 어렵게 만들기 때문에, IPMSM에서 발생된 열의 효율적인 냉각이 중요하다. 따라서 본 연구에서는 IPMSM의 냉각장치 적용을 위한 선행 연구로써 IPMSM 의 열 발생 특성 분석을 위하여 IPMSM의 각 구성품에 대한 열전달 계수를 도출하고, 열 등가회로를 구성하여 열해석을 수행하는 열해석 기법 연구를 수행하였다. 또한 IPMSM 실 모델의 열 실험 데이터와의 비교를 통한 열해석 기법의 유효성 검증을 수행하였다. In this paper, research on the thermal analysis method is reported for the characterization of heat generation while operating an Interior Permanent Magnet Synchronous Motor (IPMSM) for railway vehicles. Efficient cooling of the heat generated in the IPMSM is important because the excessive heat generated from the winding, core and permanent magnets increases the difficulty of continuously operating an IPMSM over long time periods. Therefore, in this study, in order to analyze the heat generation characteristics of the IPMSM for advanced research in the application of IPMSMs to cooling devices, the heat transfer coefficients for each component of the IPMSM were derived and the thermal equivalent circuit was configured to perform thermal analyses. Finally, the validation of the suggested thermal analysis method was performed through comparison with the heat experimental data of an IPMSM prototype.

Influence of Internal Resistance on Temperature Rising of Cylindrical Ni-MH Batteries

The internal resistance of the six Ni-MH batteries are obtained by experiment, furthermore get resistance curve using polynomial fitting method. This article commits itself to take the variation of the operating conditions into account to obtain the overall temperature rising curve and the temperature profile based on battery thermal model. The temperature rising results under different battery resistance models (R=C and R= f(t)) are compared. It is useful to provide basic reference for further study in Ni-MH battery heat generation characteristics and the improvement for battery thermal management.

Classification of Bridge Current and Analysis of Heat Transfer Characteristics in Polyvinyl-Chloride-Sheathed Flat Cord Under Tracking

In this study, we examine the tracking happen in a polyvinyl-chloride-sheathed flat cord (PVCSFC), which is widely used as a distribution cord. The study classifies the bridge current via the formed conductive paths during tracking in the PVCSFC. Further, it attempts to distinguish the characteristics of heat generation and heat transfer by kind of bridge current. When the PVCSFC is in the static state, the bridge currents flow only through the electrolyte bridge. In the case of the carbonized PVCSFC, the bridge currents flow through one or more conductive paths. One is the electrolyte bridge, the other is the bridge that is consisted electrolyte and carbonized insulation. Currents flowing through different conductive paths have different heat generation and transfer characteristics. As the bridge current flowing in the conductive path consisting of electrolyte and carbonized insulation increases, the temperature difference between the surface of the PVCSFC and ambient air also increases correspondingly.

Quantitative Thermal Imaging of Single-Walled Carbon Nanotube Devices by Scanning Joule Expansion Microscopy

Electrical generation of heat in single-walled carbon nanotubes (SWNTs) and subsequent thermal transport into the surroundings can critically affect the design, operation, and reliability of electronic and optoelectronic devices based on these materials. Here we investigate such heat generation and transport characteristics in perfectly aligned, horizontal arrays of SWNTs integrated into transistor structures. We present quantitative assessments of local thermometry at individual SWNTs in these arrays, evaluated using scanning Joule expansion microscopy. Measurements at different applied voltages reveal electronic behaviors, including metallic and semiconducting responses, spatial variations in diameter or chirality, and localized defect sites. Analytical models, validated by measurements performed on different device structures at various conditions, enable accurate, quantitative extraction of temperature distributions at the level of individual SWNTs. Using current equipment, the spatial resolution and temperature precision are as good as ∼100 nm and ∼0.7 K, respectively.

Features of operation of motor transport diesel working on ethanol and fuel emulsion

Possibility of ethanol and fuel emulsions' application as an alternative fuel for diesel engines is considered. Indicator parameters, environmental indexes and characteristics of heat generation during the diesel engine operation on ethanol and fuel emulsion are given.

HYSTERESIS CHARACTERISTICS OF HIGH MODULUS LOW SHRINKAGE POLYESTER TIRE YARN AND CORD

Abstract Hysteresis characteristics of high modulus low shrinkage (HMLS) polyester tire yarn and cord were evaluated to determine “specific work loss,” which indicate its heat generation characteristics. Test parameters were selectively chosen, considering the service conditions of high-speed passenger radial tires in which HMLS polyester tire cords are predominantly used. Specific work loss was found to increase exponentially with the increase in extent of stress relief. Dynamic property of this yarn and cord was also studied to determine “loss tangent (tan δ),” which influences rolling resistance of tires in service. A good correlation has been found between specific work loss of hysteresis test (a slow speed test) and tan δ of dynamic test (a high-speed test). Dynamic property of polyester dipped cord was investigated for a wide range of temperatures (100–180 °C) and frequencies (5–25 Hz). Tan δ at 100 °C was found to be relatively low and its magnitude remained at the same level for a wide range of frequencies. This is a favorable condition for the high-speed passenger radial tires, made out of HMLS polyester tire yarn. Microstructure of HMLS polyester yarn was analyzed. Crystallinity is around 43% (measured by Wide angle x-ray scattering); crystal width and long period are 61 and 142 Å, respectively.

Characteristics of heat generation in a quantum dot

On the basis of the nonequilibrium Keldysh Green's function technique, we study the current-induced heat generation $Q$ in a quantum dot (QD) taking both a bias voltage and a rotating magnetic field into consideration. It is found that under the conditions of small bias voltage, weak dot-lead coupling strength, and low temperature, the generated heat $Q$ is mainly decided by the probability of each electron to scatter off a phonon and shows quantum properties. As a result of this, many interesting phenomena absent in macroscopic devices appear. For example, when the bias voltage energy is slightly larger than one phonon energy but is less than that of two phonons, two peaks appear in the curve of $Q$ versus the QD level, even though only one current peak exists. In particular, the valley between the two peaks in $Q$ is the very site where the single current peak is placed, an ideal condition for device operation. However, if the above conditions are not satisfied, $Q$ behaves as in macroscopic systems, approximately proportionally to the electron current.

Electro-Thermal Scaling Analysis of Si MOSFETs with Device Length Typically Larger than 100nm

Scaling consideration is applied to the coupling electro-thermal characteristics of Si MOSFETs with device length typically larger than 100 nm. The non-equilibrium nature of the electrons and the crystal lattice is considered. Both lumped and rigorous electro-thermal models are deployed to examine the device thermal trend with device scaling. The lumped model considers the self-heating of the device and the resulting electron and lattice temperature rise. The results show that the non-equilibrium nature of electrons and phonons becomes important for devices with gate lengths typically shorter than 1 micrometer. Also, the lumped model showed an increase of the electron temperature due to the scaling trend even though the lattice temperature is kept constant. Further investigation of the heat generation characteristics revealed that hotspot predictions for devices typically shorter than 200 nm need different strategies than for larger devices.

Thermal analysis of a cylindrical lithium-ion battery

This work investigates the heat generation characteristics of a cylindrical lithium-ion battery. The battery consists of the graphite, LiPF 6 of the propylene carbonate/ethylene carbonate/dimethyl carbonate (PC/EC/DMC) solution, and spinal as anode, electrolyte and cathode, respectively. The coupled electrochemical–thermal model is developed with full consideration of electrolyte transport properties as functions of temperature and Li ion concentration. A truly conservative finite volume numerical method is employed for the spatial discretization of the model equations. Three types of heat generation sources including the ohmic heat, the active polarization heat and the reaction heat are quantitatively analyzed for the battery discharge process. The ohmic heat is found to be the largest contribution with around 54% in the total heat generation. About 30% of the total heat generation in average is ascribed to the electrochemical reaction. The active polarization contributes the least comparing to the ohmic heat and reactions heat. The results also show that the Li ion concentration and its gradient in electrolyte are the main factors giving the effect on the heat generations of active polarization and electrolyte electric resistance. The raised temperature in the battery discharge is positive related with the thickness of both separator and electrodes.

Synthesis, characterization and in vitro cytotoxicity of self-regulating magnetic implant material for hyperthermia application

Gd-substituted zinc ferrite nanoparticles with low Curie temperatures ( T c) were synthesized by a chemical co-precipitation method. The magnetic properties and heat generation characteristics of these magnetic nanoparticles were investigated. The T c of ZnGd x Fe 2 − x O 4 nanoparticles increased with increasing Gd 3+ substitution, and was ~ 318 K at x = 0.02, which was a suitable Curie temperature for thermal seeds implanted in human body. The study on heat generation ability under external alternating magnetic field showed that the temperatures of these nanoparticles could be safely controlled around T c without the temperature probe and controller. Furthermore, in vitro cytotoxicity of the ferrite nanoparticles was assessed using MTT assay. The results demonstrated that exposure to the bare ferrite nanoparticles for 48 h resulted in concentration-dependent toxicity. Cell growth inhabitation was observed when 4.0 mg/ml of bare ferrite nanoparticles was used. In contrast, PEG-capped nanoparticles had no significant effect on cell viability at any of the concentrations tested.

Potential tissue damage from transcutaneous recharge of neuromodulation implants

The magnetic-field-driven heat generation in neuromodulation systems consisting of implanted and skin-surface-mounted components gives rise to the potential of discomfort, cell damage, and possible necrosis. The skin-surface-mounted component, commonly termed the antenna, serves the function of the primary of a transformer, and the implant is the secondary. Heating occurs in both of these components during the recharging of a battery situated in the implant. Previously reported experimental data for the heat generation characteristics of three commercially available neurostimulation systems has been enhanced by further experiments carried out as part of this investigation. A numerical simulation of the temperature distribution in tissue beds adjacent to the implant and the antenna has been performed here. The aggregated data have been used as input information to a bio-heat-transfer model which yields both the spatial and temporal variations of the temperature field. It was found that during long-duration recharging periods, the temperature of the tissue rises in response to the heat generation. This information enables the identification of the magnitude and location in the tissue of the hot-spot temperature. The temporal temperature variation at the hot spot was employed in conjunction with a tissue-damage integral to identify the possibility of cell damage and/or necrosis. It was found that two of the three investigated neuromodulation systems did not give rise to temperature levels that may cause tissue damage. However, the third of the systems caused temperatures of sufficient elevation so that for recharging periods on the order of 2 h, necrosis was found to be likely in situations where heat transfer is suppressed at the surface of the skin.