近室温样品加热炉温度的模糊PID控制研究

根据红外隐身材料光谱发射率测试方法的要求,提出了一种基于半导体制冷器的近室温样品加热炉系统。在对加热炉系统特性进行分析的基础上,建立了基于模糊PID控制的系统仿真模型。经仿真及实验可知,在加热和制冷条件下,实际温度与设定温度之间的误差分别为±0.20℃和±1.00℃。结果表明,系统稳定性好,响应时间短,解决了近室温样品加热炉抗干扰能力弱、不易控制等问题。     

Three-dimensional numerical modeling of an induction heated injection molding tool with flow visualization

Using elevated mold temperature is known to have a positive influence of final injection molded parts. Induction heating is a method that allow obtaining a rapid thermal cycle, so the overall molding cycle time is not increased. In the present research work, an integrated multi-turn induction heating coil has been developed and assembled into an injection molding tool provided with a glass window, so the effect of induction heating can directly be captured by a high speed camera. In addition, thermocouples and pressure sensors are also installed, and together with the high speed videos, comparison of the induction heating and filling of the cavity is compared and validated with simulations. Two polymer materials ABS and HVPC were utilized during the injection molding experiments carried out in this work. A nonlinear electromagnetic model was employed to establish an effective linear magnetic permeability. The three-dimensional transient thermal field of the mold cavity was then calculated and compared with the experiments. This thermal field was transferred to an injection molding flow solver to compare simulations and experimental results from the high speed video, both with and without the effect of induction heating. A rapid thermal cycle was proved to be feasible in a mold with an integrated induction coil. Furthermore, it was shown that the process can be modeled with good accuracy, both in terms of the thermal field and of the flow pattern.     

塑料微流控芯片热压成形温度控制装置

采用聚合物如塑料等制作微流控芯片是拓展芯片应用,实现芯片产业化的关键。温度是塑料微流控芯片热压成形过程中的重要工艺参数。本文采用半导体热电致冷堆,设计了适合塑料芯片制作的温度控制装置;分析了升降温过程中所需的加热／制冷功率,并对升降温特性进行了研究;设计了半导体热电致冷堆供电电源装置。对温度控制装置的升／降温及温度控制精度进行了实验,并给出了实验结果。     

A fast ramp rate thermally stimulated current technique to quantify electronic charge dynamics in thin films

Thermally stimulated current (TSC) techniques have been applied to study thermally activated events in many materials. However, the temperature ramp rates in traditional TSC are typically too slow (few degrees per minute) to monitor materials whose properties are strongly time dependent. A fast ramp rate TSC (FR-TSC) technique was developed with ramp rates of 1-5 K/s. This is up to 100 times faster than traditional TSC, so that material changes can be appropriately quantified in the time scale at which they take place. In this paper, the experimental design and challenges to achieve fast and stable ramp rates and to measure the low-level currents are discussed. The fast ramps were attained using a thermoelectric cooler, controlled by a proportional-integral-derivative feedback loop, for both heating and cooling. FR-TSC measurements (1 K/s and 20-100 degrees C) on poly(vinylidene fluoride-trifluoroethylene) ferroelectric thin films are discussed as an example material. From these measurements, thermally activated currents as well as irreversible and reversible charge dynamics were readily distinguished with multiple thermal cycles. These measurements suggest that this technique holds substantial promise in quantifying charge dynamics in fast response materials.     

Control of surface temperature of an aluminum alloy billet by air flow during a heating process at elevated temperature

The procedure of semi-solid forming is composed of heating a billet, forming, compression holding and ejecting step. There are several methods to heat a billet during semi-solid forming process such as electric heating and induction heating. Usually in semi-solid forming process, induction heating has been adopted to achieve more uniform temperature of semi-solid material. Although induction heating is better method than any others, however, there is still difference of temperature between internal part and surface part of semi-solid material. Worse yet, in case of high liquid fraction of semi-solid material, liquid of the billet will flow down though solid of the billet still remains, which is very difficult to handle. In the present study, induction heating of the billet during thixoforging process with forced surface cooling has been performed to obtain more uniform distribution of temperature, microstructure and shape of the billet. Distribution of temperature of the billets was measured and compared with that of conventional distribution of temperature. Microscopic and macroscopic aspects of the billets were discussed according to location of the measuring points. By this new induction heating method, not only temperature distributions over the whole billet become uniform, but also control of temperature distribution between inside and outside part of the billet is possible as user’s experimental intentions.

     

Eliminating weldlines of an injection-molded part with the aid of high-frequency induction heating

High-frequency induction is an efficient way to heat mold surface by non-contact electromagnetic induction. It has been recently applied to injection molding because of its capability to heat and cool mold surface rapidly. This study applies high-frequency induction heating to eliminate weldlines in an injection-molded plastic part. To eliminate or reduce weldlines, the mold temperature at the corresponding weld locations should be maintained higher than the glass transition temperature of the resin material. Through 3 s of induction heating, the maximum temperature of 143 °C is obtained on the mold surface around the elliptic coil, while the temperature of the mold plate is lower than 60 °C. An injection molding experiment is then performed with the aid of induction heating, and the effect of induction heating conditions on the surface appearance of the weldline is investigated. The weldline on the heated region is almost eliminated, from which we can obtain the good surface appearance of the part.     

A novel nanofluid manufacturing process using a cylindrical flow cooling method in an induction heating system

The main purpose of this study is to develop a cylindrical flow cooling method in an induction heating system that is capable of producing the nanofluid. The system consists of a high frequency induction heating system, vacuum system, temperature control system, and a cylindrical curtain collector. The raw material Zn is evaporated by the high frequency induction heating system. The gas phase Zn is condensed and collected by a water cylindrical curtain collector. During the process, the gas phase Zn is oxidized. The ZnO nanoparticles were collected and suspended in de-ionized water. Through transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and particle size analyzer (PSA), a set of applicable parameters size can be obtained. Results show that the lower the collecting liquid temperature and the shorter the collecting distance, the smaller the nanoparticle size obtained. An aspect of UV/V is absorbency, the produced ZnO nanofluid absorbed UV when the wavelength is 360 nm to 380 nm.     

基于改进PID算法的多极射频消融治疗系统的研制

多极射频消融治疗系统是一种利用射频加热技术和热生物效应原理治疗人体肿瘤的医疗设备。通过软件控制算法和硬件调节结合，该系统实现了治疗过程中治疗温度和时间的精确控制。本文介绍了基于改进PID算法的多极射频消融治疗系统的研制，详细讨论了该系统的工作原理、硬件结构及软件结构。     

High-speed thermo-microscope for imaging thermal desorption phenomena

In this work, we describe a thermo-microscope imaging system that can be used to visualize atmospheric pressure thermal desorption phenomena at high heating rates and frame rates. This versatile and portable instrument is useful for studying events during rapid heating of organic particles on the microscopic scale. The system consists of a zoom lens coupled to a high-speed video camera that is focused on the surface of an aluminum nitride heating element. We leverage high-speed videography with oblique incidence microscopy along with forward and back-scattered illumination to capture vivid images of thermal desorption events during rapid heating of chemical compounds. In a typical experiment, particles of the material of interest are rapidly heated beyond their boiling point while the camera captures images at several thousand frames∕s. A data acquisition system, along with an embedded thermocouple and infrared pyrometer are used to measure the temperature of the heater surface. We demonstrate that, while a typical thermocouple lacks the response time to accurately measure temperature ramps that approach 150 °C∕s, it is possible to calibrate the system by using a combination of infrared pyrometry, melting point standards, and a thermocouple. Several examples of high explosives undergoing rapid thermal desorption are also presented.     

Integrated numerical analysis to evaluate replication characteristics of micro channels in a locally heated mold by selective induction

High-frequency induction heating is an efficient way to heat mold surfaces by electromagnetic induction using a non-contact procedure. Due to its ability to rapidly heat and cool mold surfaces, this method has been applied recently to the injection molding of micro/nano structures. The present study investigates a localized heating method involving the selective use of mold materials to enhance the heating efficiency of high-frequency induction heating. A composite injection mold consisting of ferromagnetic material and paramagnetic material was used for localized induction heating. The feasibility of this localized heating method was investigated through numerical analyses in terms of its heating efficiency for localized mold surfaces and the resulting flow characteristics in micro channels. To take into account the effects of thermal boundary conditions of localized induction heating, a fully integrated numerical analysis effectively connecting electromagnetic field calculation, heat transfer analysis, and injection molding simulation was carried out. The proposed integrated simulation was applied to the injection molding of a rectangular strip containing micro channels, and the resulting mold heating capacity and replication characteristics of the micro channels were compared with experimental findings in order to verify the validity of the proposed simulation.     

超声固结区域温度场分析及实验研究

温度是影响超声固结质量的重要因素,针对固结区域温度难以直接测量的现状,通过数值模拟研究工艺参数对固结温度的影响。首先,基于Hertz接触理论和Coulomb摩擦定律分析了固结区域的摩擦功,建立了固结区域的发热模型;其次,建立了钛铝箔材的超声固结三维热传导有限元模型,并且分析了主要工艺参数对固结区域温度场分布的影响;最后,为了验证模型的有效性,建立了超声固结加工温度测试平台,通过在基板埋植热电偶的方式测量固结时的温度,发现实验结果与数值仿真结果变化趋势一致,证实了模型的有效性。     

Development of roll-to-roll hot embossing system with induction heater for micro fabrication

In this paper, a hot embossing heating roll with induction heater inside the roll is proposed. The induction heating coil is installed inside a roll that is used as a heating roll of a roll-to-roll (R2R) hot embossing apparatus. Using an inside installed heating coil gives the roll-to-roll hot embossing system a more even temperature distribution on the surface of the heating roll compared to that of previous systems, which used an electric wire for heating. This internal induction heating roll can keep the working environment much cleaner because there is no oil leakage compared to the oiled heating roll. This paper describes the principles and provides an analysis of this proposed system; some evaluation has also been performed for the system. A real R2R hot embossing heating roll system was fabricated and some experiments on micro-pattering have been performed. After that, evaluation has been performed on the results.     

Improvement of efficiency and temperature control of induction heating vapor source on electron cyclotron resonance ion source

An electron cyclotron resonance ion source (ECRIS) is used to generate multicharged ions for many kinds of the fields. We have developed an evaporator by using induction heating method that can generate pure vapor from solid state materials in ECRIS. We develop the new matching and protecting circuit by which we can precisely control the temperature of the induction heating evaporator. We can control the temperature within ±15?°C around 1400?°C under the operation pressure about 10(-4) Pa. We are able to use this evaporator for experiment of synthesizing process to need pure vapor under enough low pressure, e.g., experiment of generation of endohedral Fe-fullerene at the ECRIS.     

Design and performance of a new induction furnace for heat treatment of superconducting radiofrequency niobium cavities

Superconducting radio frequency (SRF) cavities made of high purity niobium (Nb) are the building blocks of many modern particle accelerators. The fabrication process includes several cycles of chemical and heat treatment at low (～120 °C) and high (～800 °C) temperatures. In this contribution, we describe the design and performance of an ultra-high-vacuum furnace which uses an induction heating system to heat treat SRF cavities. Cavities are heated by radiation from the Nb susceptor. By using an all-niobium hot zone, contamination of the Nb cavity by foreign elements during heat treatment is minimized and allows avoiding subsequent chemical etching. The furnace was operated up to 1400 °C with a maximum pressure of ～1 × 10(-5) Torr and the maximum achievable temperature is estimated to be higher than 2000 °C. Initial results on the performance of a single cell 1.5 GHz cavity made of ingot Nb heat treated at 1200 °C using this new induction furnace and without subsequent chemical etching showed a reduction of the RF losses by a factor of ～2 compared to cavities made of fine-grain Nb which underwent standard chemical and heat treatments.     

Transient response of a thermoelectric generator subjected to spatially non-uniform heating: Implications for heat and IR sensing applications

We present a combined experimental and computational investigation of the transient behavior of a thermoelectric generator (TEG) subjected to temperature gradients of less than 0.5 K across its thickness. Such conditions can exist when TEGs are used as heat sensors or IR detectors. Spatially non-uniform heating was initiated by allowing light to strike the central portion of one side of the TEG or by placing a small heated probe in contact with that surface. The time-dependent, open circuit voltage output of the TEG was predicted using temperature results from a three dimensional transient heat conduction finite element model. It is shown that the transient voltage output is influenced by the configuration of the mounting hardware, by the thermal properties of the TEG’s materials of construction, and by convection. Three-dimensional heat conduction in the TEG determines the nature of the transient voltage output, which, in some cases, exhibits an overshoot.     

对称型梯度功能陶瓷材料的非定常热应力

采用摄动法推导出对称型梯度功能材料平板的一维非定常温度场及非定常热应力场的解析表达式，对Ａｌ２Ｏ３／（Ｗ，Ｔｉ）Ｃ系对称型梯度功能陶瓷平板表面冷却及加热过程中的非定常温度场及非定常热应力场进行了计算。讨论了提高陶瓷刀具材料抗热震性的方法即采用梯度功能陶瓷刀具材料，并结合断续车削试验进行了验证。     

95CrMo锥形钎杆热处理工艺的探索

通过对95CrMo钎杆经过相同的温度加热保温,分别进行风冷、空冷、缓冷,以及两种不同加热方式处理之后,对比四种工艺处理的差异及与中空钢原材料的检验分析比较,研究表明在相同中空钢原材料的前提下,随着冷却速度的加快,沿晶碳化物级别越低,硬度越高;在相同加热温度和冷却条件下,感应加热处理的珠光体类型组织比井式炉加热处理的珠光体类型组织更细。     

Control of a Thermoelectric Brain Cooler by Adaptive Neuro-Fuzzy Inference System

Abstract

In this study, neuro-fuzzy control of a thermoelectric head cooler system (thermoelectric helmet) is developed for brain hypothermia applications. Hypothermia is a medical treatment method of protecting the brain, in which the temperature of the brain drops below the critical level for reducing oxygen consumption of tissues. The brain should be kept at a certain temperature by a suitable control for hypothermia applications. The temperature of the thermoelectric head cooler system changes according to the current intensity supplied. The control of the thermoelectric head cooler system was performed according to the initial membership functions, which was determined by an expert using fuzzy logic control. The system was modeled by an adaptive neuro-fuzzy inference system (ANFIS). The data were then entered into the system and new membership functions were determined. By this way, learning ability of the artificial neural network and the abilities of fuzzy logic, such as decision making, were combined and a more effective solution was developed. The system software can be reprogrammed with the new membership functions.     

Study on the plane induction heating process strengthened by magnetic flux concentrator based on response surface methodology

In the surface heat treatment process of metals, the induction heating strengthened by ferromagnetic metal powder bonded magnetic flux concentrator (MPB-MFC) possesses more advantages due to its high efficiency. However, the further research of strengthen mechanism of MPB-MFC is still needed. It is necessary to establish the analytical model for accurately control and optimization of the plane induction heating process with MPB-MFC. In this paper, the coupled electro-magnetic-thermal multi-physics FEM model of the MPBMFC assisted induction heating is established, which involves the consideration of the temperature dependent thermal and magnetic material properties. The comparison between the results of several middle-frequency experiments and the simulation proves that the precision of simulation model is reliable. In addition, the influence of combined input variables on the final temperature is studied based on the response surface methodology (RSM), which could provide a comprehensive understanding for the process control and optimization in industrial production.

     

基于微机电系统技术的微型热电致冷器研究进展

介绍热电材料、热电器件的原理及发展历史,从材料及结构两方面,对基于微机电系统加工工艺的微型热电致冷器的最新研究进展进行综述,比较不同材料及不同结构的性能特点,对块体热电材料和低维热电材料的研究进展进行介绍,着重分析超晶格薄膜材料及Cross-Plane型器件,指出研究具有更高优值系数的新型材料,在维持Seebeck系数不变的同时提高电导率并降低热导率,及采用新的加工工艺优化致冷器的结构,减小接触电阻、接触热阻等,是提高热电致冷器性能的有效手段。