基于MC68HC11单片机电加热炉炉温控制系统

电加热炉炉温智能控制系统的研究是基于先进的单片机控制技术,在低能耗下实现对炉温的精确控制.本文选用单片机组成电加热炉炉温控制系统,计算机定时对炉温进行测量,把测量的温度信号经A/D转换后送入到计算机,按预定的控制规律进行判别和运算.从而得到控制量,作为电加热炉的触发信号,用来控制电加热的温度变化,以达到炉温控制曲线的要求.     

改善二位式温度控制系统调温效果的方法

本文分析了二位式温控系统调温特性，提出了两种改善炉温控制效果的措施，分别对其控温原理进行了详细分析和比较，并给出了控温曲线及具体电路形式。     

风冷螺杆热泵机组的除霜控制设定参数优化的试验研究

试验研究了除霜进入条件和除霜退出条什两个除霜控制设定参数对风冷热泵机组的冬季除霜的影响,基于多次连续的除霜循环和制热循环的测试数据,揭示了不同的除霜控制设定参数值下,机组在除霜循环运行和制热循环运行时,翅片温度、出水温度、吸气过热度和过冷度等运行参数以及制热量的变化特点和变化规律,为除霜控制逻辑中优化除霜控制设定值,提高机组平均制热能力和运行效率,提高制热运行可靠性提供了极其重要的数据参考.     

一种改进的试验机高温炉温控方案

针对材料试验机高温炉温控方面的问题,即实际试样温度与调节器的控制显示温度不一致的问题,提出了一种改进的试验机高温炉温控设计方案,即串级控制方案。结果表明:采用该方案可较好地解决实际试样温度与调节器的控制显示温度不一致的问题,从而实现对试样加热温度的精确控制,该方案可供炉子及炉温控制设计人员参考。     

氧化铝陶瓷金属化层温度分析研究

工艺温度是影响陶瓷金属化质量的关键因素之一,针对高温氢炉中陶瓷金属化层温度难以实时测量的问题,本文建立氧化铝陶瓷金属化过程的三维流动传热数学模型。模型采用随温度变化的动态材料物性参数,考虑辐射、对流、传导三种传热形式,利用有限体积法求解陶瓷金属化过程中炉内的流动与传热问题,获得陶瓷金属化温度实时变化曲线。瞬态计算结果表明不同位置处最高烧结温度相差26℃,且比金属化工艺设定温度曲线低20~40℃,这为优化氢炉结构、进一步提高炉温均匀性提供参考依据。     

液体化学品自燃温度试验中温度控制器性能仿真

GB/T 21860-2008(液体化学品自燃温度的试验方法)是液体化学品自燃温度测定方法的标准,若采用常规PID(比例、积分、微分)温度控制存在超调会影响试验结果精确度.根据坩埚炉低温区间升温速度快、高温区间升温速度慢的特点,以及国家标准中要求以30℃和3℃进行温度调节,对坩埚炉当前温度和所需调节温度两个变量进行模糊化处理,建立此坩埚炉的模糊控制规则库,构造坩埚炉温度的模糊PID控制器.在仿真情况下,模糊PID控制没有超调,控温精度达到目前国外产品同等水平.模糊PID控制器的设计,为实际试验过程中的坩埚炉温度控制器设计积累了经验,寻找到了方向.     

两种组合钢框架火灾变形性能的试验研究

利用自行研制的火灾加温试验炉及相关测试装置,对2种不同连接方式共4榀组合钢框架在不同的火灾工况下的火灾变形性能进行了试验研究,火灾工况包括:梁、板、柱同时受火而节点不受火和梁、板受火而柱、节点不受火2种。试验中量测了炉温,H型钢梁、柱及钢筋混凝土楼板中的温度分布,结果表明:裸钢的温度相差很小,而埋入混凝土中的钢的升温曲线与裸钢的有较大差异;混凝土的升温曲线则与钢的升温曲线差别较大,加温初期不久由于混凝土凝结水等的原因致使温升曲线存在有一平缓阶段,且随着距受火面距离增大混凝土的温升曲线有明显的滞后现象,当炉温和裸钢的温度开始下降时,混凝土的温度却仍在升高。该文对框架的变形和组合梁变形进行了分析,经比对2种连接方式组合钢框架的火灾行为后,给出了工程应用建议。     

改善二位式调节仪表控制炉温精度方法探讨

本文对实验室所使用的恒温箱和高温炉采用二位式温度调节仪控制炉温,提出在不增加用户较大成本的情况下来改善炉温温度波动度、温度均匀性、温度偏差的几种方法。     

温度测量与控制装置制作和改进经验二则

工业生产的许多场合和工艺都需要对温度进行测量和控制，且往往要求被控温度保持在预先设定的范围内(即恒温控制)。以下介绍我们在烘茶工艺中使用的自制温度测量与恒温控制装置(见图1)，它的恒温范围可据要求灵活调整，当被控温度达到或低于下限温度值时，电热器通电升温，当温升达到上限温度值时，电热器便断电不工作，     

炉温测试仪校准方法的探讨

炉温测试仪主要用于测量波峰焊、回流焊等设备的测温曲线,以便更好的改进制程和工艺。文章简述了炉温测试仪装置的结构和使用,对炉温测试仪的校准方法进行探讨,并通过试验数据和不确定度评定验证方法的可行性以及指出了注意事项。     

A New Generation of Open Zinc Freezing Point Cells at TUBITAK UME

The Temperature Laboratory at TUBITAK UME initiated a study which focused on the construction of freezing point cells of ITS-90 as primary temperature standards. The first cell constructed within the scope of this study was an open tin freezing point cell and the results were in good agreement with the reference tin fixed point cell of UME. The second set of cells constructed was two open zinc freezing point cells. The design of these cells is similar to the tin freezing point cell. After construction, all the home-made cells were evaluated by analyzing their melting and freezing curves. Finally comparison measurements were performed between the current laboratory reference zinc cell and all newly constructed cells.     

The Effect of Low Level Antimony on the Tin Temperature Fixed Point

Impurities are a major source of uncertainty in the temperature of a thermometry metal fixed point (of the order of 1 mK). A better understanding of the impurity effect is required to improve top-level metrological thermometry. This investigation reports on some unusual effects of antimony doped into a high-purity (99.9999%) tin sample. The change in temperature and shape of the melting and freezing curves of the tin, caused by low concentrations of the Sb dopant, were measured in order to test the interpolation of previous data. Most historical experiments have worked at much higher impurity concentrations??say of the order of 100 ppm??and in arrangements that are not used on a day-to-day basis in a metrology laboratory. These measurements on the tin were done after doping at mass fractions of approximately (1 and 25) parts per million by weight (ppmw) of antimony. Repeated melting and freezing curves, before and after doping, confirmed the reproducibility of the temperature measurements in this tin cell. The freezing temperature of the tin after adding antimony was higher than for ??pure?? tin. However, the temperature change was less than expected, being an average (+0.06±0.03) mK · ppmw^?1. Samples from the tin were analyzed by glow discharge mass spectrometry (GD-MS) before and after doping to detect the distribution of all the impurity elements. If the dopant level detected by GD-MS was used, then a value of (0.18 or 0.29) mK · ppmw^?1 was calculated (much closer to the value interpolated from earlier works). There was evidence that the thermal history of metal phase transitions can cause considerable segregation of some impurities and that the effects of this segregation can be clearly seen on the shape of the melting curves of tin doped with Sb. (The segregation might be more pronounced as Sb forms a peritectic in tin, i.e., a ??positive?? impurity which increase the phase transition temperature).     

Investigation of CTARA wood-burning stove. Part II. Analytical investigation

A theoretical framework for predicting the performance of theCtara stove under different geometric and operating conditions has been developed by writing energy balance conditions over appropriate control volumes under a steady-state assumption. Equations are derived for predicting the fuel burning rate, air flow ingress through primary and secondary ports, wall temperatures, gas temperatures, wood-surface temperature and the vessel heat absorption rate. Complete chemical reaction is assumed to take place inside the stove and radiation heat transfer between products of combustion and the enclosing surfaces has been accounted. The analytical framework results in thirteen strongly coupled algebraic equations that are solved iteratively on a computer. The framework predicts magnitudes of efficiency and excess-air factors for various geometric parameters (e.g. height of stove, height of the grate, port-opening diameter, stove diameter etc.) and operating parameters (power of the stove, ratio of volatiles to char in wood, vessel dimensions etc.). The predictions are found to be plausible in magnitude and in trends and compare favourably with experimental results presented in Part I with one exception. Whereas experimental results show a negligible effect of power on efficiency, the predictions indicate an increase in efficiency with power.     

The performance of Thai charcoal stove

Wood and charcoal used for cooking accounts for nearly 50% of the energy consumption in Thailand. Deforestation has become a problem and the continuing population growth puts ever increasing demands on the wood and fuel supply. This report looks at the performance of a typical Thai charcoal stove used under 18 different operating conditions and identifies the major heat losses. When used in the most economic mode, the major losses are to the stove wall and in generating steam. Heat transfer to the pan is primarily by radiation, convective heat transfer is poor and the heat in the flue gas is mainly wasted. By controlling the air input a saving of about 30% in the charcoal can be made. The Thai stove as developed over the past 200 years is probably not far from the best that can be achieved using local low-cost materials.     

Thermal Analysis of the Heater-Induced Realization of the Tin Fixed Point

In this article, work concerning the thermal analysis of the tin fixed-point is reported. First, the development of a new fixed-point furnace is described. Improvements in the design of the furnace and in the control system enable measurement of the heater power during the phase change. The furnace is sufficiently thermally insulated to produce excellent uniformity and stability, leading to high quality freeze-initiation and minimal thermal influences on the freezing point. By employing the improved furnace and newly-fabricated tin fixed-point cells, the start and end of the melting plateau and the end of the freezing plateau were accurately determined, enabling reliable evaluation of the liquid fraction during the realization of the tin fixed-point compared to conventional methods. Two open-type tin fixed-point cells were fabricated using high-purity tin that was chemically analyzed for impurity content. Thermal analysis results of freezing-point depression are compared to those based on the chemical analysis.     

Correlation Between Immersion Profile and Measured Value of Fixed-Point Temperature

Assessment of thermal immersion effects in the melting and freezing points defined by the International Temperature Scale of 1990 is one of the vital issues of modern thermometry. In documents of the Consultative Committee for Thermometry, the deviation of the experimental immersion profile from the theoretical value of the hydrostatic effect at a height of about 3 cm to 5 cm from the thermometer well bottom is used for the estimation of the uncertainty due to unwanted thermal effects. This estimation assumes the occurrence of solely the hydrostatic effect all along the height of the well inner wall. Real distortions of the temperature gradient at the bottom and at the top part of the well caused by the change of heat-exchange conditions are not taken into account. To define more precisely the temperature gradient along the height of the well, a miniature PRT with a 30 mm sensitive element and a sheath length and diameter of about 60 mm and 6 mm, respectively, were used. Also, the measurements of fixed-points temperature at noticeably different slopes of immersion profiles due to variations of the thermometer heat exchange and phase transition realization conditions were produced by means of a standard platinum resistance thermometer (SPRT). The measurements were carried out at the tin and zinc freezing points. The immersion curves measured with a miniature thermometer demonstrated an increase of the temperature during its lifting in the first 1 cm to 3 cm above the bottom of the well. The measurement results at the zinc freezing point by means of the SPRT have not confirmed the correlation between the immersion curves, the received value of the Zn freezing temperature, and the estimation of its uncertainty.     

Estimating the Contribution of Impurities to the Uncertainty of Metal Fixed-Point Temperatures

The estimation of the uncertainty component attributable to impurities remains a central and important topic of fixed-point research. Various methods are available for this estimation, depending on the extent of the available information. The sum of individual estimates method has considerable appeal where there is adequate knowledge of the sensitivity coefficients for each of the impurity elements and sufficiently low uncertainty regarding their concentrations. The overall maximum estimate (OME) forsakes the behavior of the individual elements by assuming that the cryoscopic constant adequately represents (or is an upper bound for) the sensitivity coefficients of the individual impurities. Validation of these methods using melting and/or freezing curves is recommended to provide confidence. Recent investigations of indium, tin, and zinc fixed points are reported. Glow discharge mass spectrometry was used to determine the impurity concentrations of the metals used to fill the cells. Melting curves were analyzed to derive an experimental overall impurity concentration (assuming that all impurities have a sensitivity coefficient equivalent to that of the cryoscopic constant). The two values (chemical and experimental) for the overall impurity concentrations were then compared. Based on the data obtained, the pragmatic approach of choosing the larger of the chemical and experimentally derived quantities as the best estimate of the influence of impurities on the temperature of the freezing point is suggested rather than relying solely on the chemical analysis and the OME method to derive the uncertainty component attributable to impurities.     

半实物仿真的电加热炉系统辨识与模糊控制

以电加热炉为实验对象,建立基于MATLAB/Simulink的电加热炉炉温半实物仿真控制系统.通过系统辨识方法得到电加热炉的准确数学模型,使用模糊PD控制策略,先通过计算机仿真方式得到合适的控制器规则和参数,再将此控制器应用到对电加热炉的实际控制当中,对电加热炉的炉温进行控制,达到了较为理想的控制效果.实验表明,半实物仿真方法在系统建模和设计控制器、寻找合适控制器参数等方面具有方便、准确等优点,可以广泛应用到工业控制的压力、液位等其他方面的控制.     

北京凤凰热处理常化炉浅析

本文以由北京凤凰设计、河北钢铁集团舞阳新宽厚板有限公司使用的热处理常化炉为例，简要介绍了该常化炉的电控特性、仪控特性和在实际使用过程中的一些具体情况和分析。