MEASUREMENT OF MEAN SPECIFIC HEAT OF PLATE GLASS AT HIGH TEMPERATURES

The mean specific heat of a typical plate glass and Solex “S” were determined in the range 500° to 100°C. The values at 1000°C. are 0.301 and 0.309, respectively, and vary as a straight-line function with temperature.     

INVESTIGATION OF IMPINGEMENT HEAT TRANSFER COEFFICIENT AT HIGH TEMPERATURES

ABSTRACT

Very little information exists for the impingement heat transfer coefficient at high temperatures. All available empirical correlations are mainly based on experiments conducted at relatively low impingement temperatures, and thus cannot describe the heat transfer characteristics of the impingement air at high temperatures with sufficient accuracy. A comprehensive study of the impingement heat transfer coefficient at high temperatures is carried out and presented in this paper. The aim of the study is to give a summary of the experimental results of the impingement heat transfer covering a large impingement air temperature range from 100 to 700°C. Heat transfer measurements were carried out on a laboratory-scale test rig. The main parts of the rig were a fan, a gas burner for air heating, a heavily insulated nozzle array with 300 × 500 mm impingement surface, a 40 mm thick and 300 × 500 mm sized aluminium plate for determination of heat transfer, and a data acquisition system. The heat transfer rate was determined from the heat-up rate of the aluminium plate due to the high temperature jet impingement.     

INVESTIGATION OF IMPINGEMENT HEAT TRANSFER COEFFICIENT AT HIGH TEMPERATURES

Very little information exists for the impingement heat transfer coefficient at high temperatures. All available empirical correlations are mainly based on experiments conducted at relatively low impingement temperatures, and thus cannot describe the heat transfer characteristics of the impingement air at high temperatures with sufficient accuracy. A comprehensive study of the impingement heat transfer coefficient at high temperatures is carried out and presented in this paper. The aim of the study is to give a summary of the experimental results of the impingement heat transfer covering a large impingement air temperature range from 100 to 700°C. Heat transfer measurements were carried out on a laboratory-scale test rig. The main parts of the rig were a fan, a gas burner for air heating, a heavily insulated nozzle array with 300 × 500 mm impingement surface, a 40 mm thick and 300 × 500 mm sized aluminium plate for determination of heat transfer, and a data acquisition system. The heat transfer rate was determined from the heat-up rate of the aluminium plate due to the high temperature jet impingement.     

CONVERSION OF CERTAIN REFRACTORY OXIDES TO A SUBOXIDE FORM AT HIGH TEMPERATURES *

A preliminary survey of the information published in the fields of chemistry and physics on the suboxide forms of SiO, TiO, ZrO, CrO, AlO, BO, VO, and CbO indicates a new field to be explored in determining the role of these suboxides in the service and failure of refractories and in the chemistry of slags. Several phenomena at the present time little understood, such as devitrification in reducing atmospheres, volatilization of refractory oxides, and certain slag types now classed as anomalous, may find their explanation in the decomposition of the oxides to low oxide forms under the favorable conditions of high temperature and low oxygen pressure which characterize much of their service.     

氧化物添加剂对CaSO4高温稳定性的影响

用 ZCL自动测硫仪研究了不同系列的氧化物对固硫产物 Ca2 SO4高温稳定性的影响 ,结果表明 :添加碱土金属氧化物能减少 Ca SO4高温分解 ;添加一定比例的 Si- Al复合氧化物对Ca SO4的稳定有明显促进作用 ;添加一定比例的 Si- Fe- Ca复合氧化物也有很好的抑制 Ca SO4高温分解的效果 ,并对其机理进行了探讨 .     

THE ACCURATE MEASUREMENT OF HIGH TEMPERATURES1

The standard temperature scale is defined and methods of realizing it both in laboratory and in factory practice are outlined. Methods of measuring temperature from very low values to the highest obtainable are described. The use of thermocouples, the errors encountered in the use of both base metal and rare metal thermocouples, and the methods used to avoid these errors are discussed. Thermocouples are useful in measuring temperatures up to about 1000 to 1500°C. Beyond the range of thermocouples and sometimes even in this range it is necessary to use some means of measuring temperature that depends on the energy radiated from the source under consideration. For this class of work the optical pyrometer is recommended as one very good method. Different forms of optical pyrometers are discussed and the advantages and disadvantages of these types are pointed out. The conclusion is reached that for many types of work the disappearing-filament type of optical pyrometer has certain advantages over other forms. Some of these advantages are pointed out and reasons given for the selection of this pyrometer. The necessity for the use of a monochromatic screen with a pyrometer is discussed and a list of the various screens available are given. Reasons are given for the general choice of a red screen for this work. In the use of an optical pyrometer it is at times necessary to know something concerning the wave-length of the light used. This brings up the question of the effective wave-length of the screen used. The effective wave-length is defined and methods given for determining and using this effective wave-length in optical pyrometry. It is shown that with a well-calibrated screen just as definite results can be obtained as with a spectrometer for determining wavelength, and the advantages of the screen over the spectrometer are set forth. Methods of calibrating optical pyrometers are discussed which bring in the idea of a black body. Methods of realizing the theoretical black body are given together with some experimental results along this line. The use of absorbing screens in extending the scale of an optical pyrometer is outlined and methods are given of obtaining the transmission of the absorbing screens so that it is easy to calculate the extension of the temperature scale with a particular screen. The kind of an absorbing screen needed for this work is shown and the advantages and disadvantages of the absorbing screens are given. Accuracy tests are included in which it is shown that very good agreement can be obtained in the use of a disappearing-filament optical pyrometer by untrained or slightly trained observers. Results are also given to show what accuracy may be expected from experienced observers from this form of pyrometer.     

工艺条件对低温烧结90氧化铝陶瓷显微结构及性能的影响

本文使用CaO-MgO-BaO-SiO2-ZrO2作为90氧化铝陶瓷的烧结助剂,在1420℃烧结得到了密度达3.77g/cm3的90氧化铝陶瓷。探讨了氧化铝粉末的活性、原料细度、成型工艺、烧结温度和保温时间等工艺条件对氧化铝陶瓷的烧结密度及其显微结构的影响。结果表明:活性高细度小的氧化铝粉末可显著降低氧化铝陶瓷的烧结温度,提高烧结体的密度;等静压成型与模压成型试样的烧结密度相近,但前者的强度则比后者提高了60~80%;其它工艺条件对氧化铝陶瓷的结构及性能的影响不显著。     

FURTHER STUDIES OF PORCELAIN GLAZES MATURING AT HIGH TEMPERATURES1

The investigation covers three fields of glazes: Series A contains 21 glazes with variations in composition as shown in the formula . Series B contains 10 glazes, each having the formula but having their clay content varying triaxially between Florida kaolin, North Carolina kaolin, and Kentucky ball clay No. 4. Series C contains 20 glazes with variations in composition as shown in the formula . The method of experimentation consists of grinding the corner glazes of each series wet, for 18 hours, cross blending the corner glazes to produce the intermediate glazes, applying the glazes by dipping to green porcelain discs, and firing them in commercial periodic and tunnel kilns to temperatures between cone 16½ and cone 19 flat. The glazes were examined with the naked eye and a 10 X pocket lens. The triaxial replacement of CaO by MgO and BaO , as tested, makes practically no change in the appearance of the glazes. With the pocket lens the bubbles in the glazes appear smaller and more numerous, near the BaO apex. When fired in the periodic kilns for 42 hours the transparency of all the glazes in- creases with the temperature. The glazes fired in the tunnel kiln to cone 19 flat in 31 hours are more opaque and smoother than in the periodic kiln at three cones lower temperature. The triaxial replacement of the Florida kaolin, by North Carolina kaolin and Kentucky ball clay No. 4 produces relatively little change in the fired appearance. The glazes containing all ball clay or a mixture of ball clay and North Carolina kaolin overfire at a lower temperature than do those containing all kaolin or a mixture of Florida kaolin and ball clay. The best glazes with 0.2 K₂O and 0.8 CaO have approximately an alumina: silica ratio of 1:9 and 1:11 for the field covered. These glazes are generally more trans- parent than the glazes with 0.3 K₂O; otherwise the results are similar. The conclusions are : (1) that the nature of the firing conditions are of the utmost importance in the development of a glaze, and (2) that an intelligent choice between glazes of equally desirable appearance requires a resort to petrographic method and mechanical tests.     

THIN-LAYER DRYING CHARACTERISTICS OF ROUGH RICE AT LOW AND HIGH TEMPERATURES

Abstract

Thin-layer drying characteristics of rough rice were determined at temperature ranging from 11.8 to 51 °C and for relative humidities ranging from 37.1% to 91.3%, with initial moisture contents in the range of 24.7 to 41.6% dry basis. An oven, a self contain air conditioning unit, recently developed in Japan, was used for this experiments. With this apparatus, very smooth drying curves were obtained. The data of sample weight, and dry and wet bulb temperatures of the drying air were recorded continuously throughout the drying period for each test. The drying process was terminated when the moisture content change in 24 h was less than 0.2 % d.b. (weight change was less than 0.05 g). The final points were recorded as the dynamic equilibrium moisture contents.

The drying data were than fitted to the Page model. The model gave a very good fit for the moisture content with an average standard error of 0.294 % d.b? Both the drying parameters, K and N, are function of drying air temperature and relative humidity. The effect of variable initial moisture content was also described effectively by the empirical Page model. The drying time employed had a large effect on the K and N values. The results presented here, over typically 5 day drying, will be useful in the long term moisture transfer process occurring during ventilated storage.     

临界点附近水的等容比热

本文分析了临界物态的一般特性。提出了一种新的计算临界点附近水的等容比热的方法与公式。对水的单相区、二相区和界面曲线的等容比热进行计算,其结果令人满意。该计算公式既简单又准确,适用于实验设备和工程设计应用。     

THIN-LAYER DRYING CHARACTERISTICS OF ROUGH RICE AT LOW AND HIGH TEMPERATURES

Thin-layer drying characteristics of rough rice were determined at temperature ranging from 11.8 to 51 °C and for relative humidities ranging from 37.1% to 91.3%, with initial moisture contents in the range of 24.7 to 41.6% dry basis. An oven, a self contain air conditioning unit, recently developed in Japan, was used for this experiments. With this apparatus, very smooth drying curves were obtained. The data of sample weight, and dry and wet bulb temperatures of the drying air were recorded continuously throughout the drying period for each test. The drying process was terminated when the moisture content change in 24 h was less than 0.2 % d.b. (weight change was less than 0.05 g). The final points were recorded as the dynamic equilibrium moisture contents.

The drying data were than fitted to the Page model. The model gave a very good fit for the moisture content with an average standard error of 0.294 % d.b¨ Both the drying parameters, K and N, are function of drying air temperature and relative humidity. The effect of variable initial moisture content was also described effectively by the empirical Page model. The drying time employed had a large effect on the K and N values. The results presented here, over typically 5 day drying, will be useful in the long term moisture transfer process occurring during ventilated storage.     

THE ROLE OF SPECIFIC HEAT IN THE SELECTION OF REFRACTORIES1

A brief discussion of specific heats is given in which particular emphasis is placed upon its determination at high temperatures, the methods which have been used in the past for its determination, and the application of the values in the selection of refractories. The need of determining physical properties of brick which have been in service is pointed out.     

A PROGRESS REPORT ON THE DEVELOPMENT OF AN ABRASION TEST FOR REFRACTORIES AT HIGH TEMPERATURES1

A report of progress in the development of a method of testing refractories for their resistance to abrasion at high temperatures. The method developed consists of a steel chisel point moving back and forth over faces of the brick clamped together. Eleven brick are tested at one time. The chisel is actuated by means of a jack hammer and is water-cooled. The blow delivered vanes from 6.5 inch-pounds at the beginning of the test to 13 inch-pounds under the most severe conditions. The chisel has a rounded point l/8-ch radius and 1 inch wide. Data show that the principle is correct and capable of differentiating between brick of varying resistances to abrasion at tempcratures as high as 1350°C.     

陶瓷及其复合材料高温自润滑的研究现状

本文就固态润滑组元性质、与陶瓷基体界面特性以及摩擦化学反应膜层等几方面因素对陶瓷自润滑效应的影响,简要介绍了当前自润滑金属陶瓷材料、自润滑陶瓷复合材料和结构陶瓷自身润滑功效的一些研究情况。总结了自润滑陶瓷材料研究中存在的不足,并提出了今后研究应注意的问题。     

高温低热导率隔热材料的研究现状及进展

新型隔热材料的一个重要发展方向是具有高温低热导率的复合材料的研究和开发。重点对硅酸铝纤维、六钛酸钾晶须及气凝胶二氧化硅隔热材料的特点进行了综述,探讨了几种颇具前景的高效高温隔热材料。     

高镁瓷工艺特性研究和应用

本文总结了ＭｇＯ－ＳｉＯ２－Ａｌ２Ｏ３系的高镁瓷配方、增塑及烧成工艺特性的研究过程与应用结果；介绍了适应大生产的高镁瓷制作工艺。     

SOME PROPERTIES OF SODA-SILICA GLASSES AT HIGH TEMPERATURES*

A study is made of density, expansion, surface tension, parachor, and viscosity data for glasses in the system Na₂O-SiO₂ within the temperature range 900° to 1400°C. The best values have been selected and correlated with composition.     

低温法高聚合度聚氯乙烯聚合度的调节

根据氯乙烯聚合机理，由低温法合成高聚合度聚氯乙烯实验数据，拟合得到平均聚合度与温度、引发剂浓度的关系式：Ｐ＝１／｛１３４００ｅｘｐ（－４５０００／ＲＴ）＋１００ｅｘｐ（－２０５００／ＲＴ）［Ｉ］／［Ｍ］｝，向单体、引发剂链转移常数与温度的关系式：Ｃ＿Ｍ＝１３４０Ｏｅｘｐ（－４５０００／ＲＴ），Ｃ＿Ｉ＝１００ｅｘｐ（－２０５００／ＲＴ）。