ImageVerifierCode 换一换
格式:PDF , 页数:4 ,大小:65.21KB ,
资源ID:527500      下载积分:5000 积分
快捷下载
登录下载
邮箱/手机:
温馨提示:
如需开发票,请勿充值!快捷下载时,用户名和密码都是您填写的邮箱或者手机号,方便查询和重复下载(系统自动生成)。
如填写123,账号就是123,密码也是123。
特别说明:
请自助下载,系统不会自动发送文件的哦; 如果您已付费,想二次下载,请登录后访问:我的下载记录
支付方式: 支付宝扫码支付 微信扫码支付   
注意:如需开发票,请勿充值!
验证码:   换一换

加入VIP,免费下载
 

温馨提示:由于个人手机设置不同,如果发现不能下载,请复制以下地址【http://www.mydoc123.com/d-527500.html】到电脑端继续下载(重复下载不扣费)。

已注册用户请登录:
账号:
密码:
验证码:   换一换
  忘记密码?
三方登录: 微信登录  

下载须知

1: 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。
2: 试题试卷类文档,如果标题没有明确说明有答案则都视为没有答案,请知晓。
3: 文件的所有权益归上传用户所有。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 本站仅提供交流平台,并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。

版权提示 | 免责声明

本文(ASTM E377-1996(2002) Standard Practice for Internal Temperature Measurements in Low-Conductivity Materials《烧蚀材料内部温度的测量》.pdf)为本站会员(feelhesitate105)主动上传,麦多课文库仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知麦多课文库(发送邮件至master@mydoc123.com或直接QQ联系客服),我们立即给予删除!

ASTM E377-1996(2002) Standard Practice for Internal Temperature Measurements in Low-Conductivity Materials《烧蚀材料内部温度的测量》.pdf

1、Designation: E 377 96 (Reapproved 2002)Standard Practice forInternal Temperature Measurements in Low-ConductivityMaterials1This standard is issued under the fixed designation E 377; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t

2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers methods for instrumenting low-conductivity specimens for testing in an environment su

3、bject torapid thermal changes such as produced by rocket motors,atmospheric re-entry, electric-arc plasma heaters, and so forth.Specifically, practices for bare-wire thermocouple instrumen-tation applicable to sheath-type thermocouples are discussed.1.2 The values stated in inch-pound units are to b

4、e regardedas the standard. The metric equivalents of inch-pound unitsmay be approximate.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices

5、 and determine the applica-bility of regulatory limitations prior to use.2. Significance and Use2.1 Internal temperature measurements are made on bothin-flight vehicles and on-ground test specimens; and, becauseof the importance of the temperature measurements to thedesign of various missile and spa

6、cecraft heat shields, it isessential that care be taken to minimize the sources of error inobtaining these measurements.2.2 Over the past several years, the problems of usingthermocouples to obtain accurate temperature measurements inlow-conductivity specimens have been studied by variouspeople to i

7、solate the sources of error and to establish improvedtemperature measurement techniques. The major sources oferror are listed in this document and recommended solutions tothe problems are given.3. General3.1 Before proceeding to the major sources of error, it isassumed that the reader is familiar wi

8、th basic methods offorming and using thermocouples2, that is (1) electric weldingto form junctions, (2) maintaining cleanliness of junction areaand lead wires, (3) proper selection of thermocouple type andsize, corresponding to both the temperature range to bemeasured and the chemical compatibility

9、with the environ-ment, and (4) proper use of instrumentation for readout ofthermocouple emf.NOTE 1Reader is referred to ASTM MNL 12, and STP 492, as wellas Kinzie, P.A., Thermocouple Temperature Measurement, for neededinformation.3.2 The most important sources of error beyond the abovebasic areas ar

10、e the following:3.2.1 The thermal disturbance produced in the low-conductivity material at the vicinity of the thermocouple sensorhot junction due to the sensor size, configuration, and instal-lation method.3.2.2 Electrical shorting of lead wires due to the electricalconductivity of the virgin or ch

11、arred ablation material, and3.2.3 Thermocouple sensor hot junction location accuracy.4. Thermal Disturbance at Vicinity of ThermocoupleSensor Hot Junction4.1 GeneralIdeally, to measure the true internal tempera-ture of a solid body, it would be desirable not to have anyforeign substance present that

12、 would create a disturbanceaffecting the natural flow of heat in the body. Since it isphysically impossible to exclude the temperature sensor fromthe internal confines of the body, it is necessary that the thermaldisturbance introduced by the sensor be minimized for accuratetemperature measurements.

13、4.2 Thermocouple Junction Bead Diameter:4.2.1 GeneralExcessively large junction beads result inlower than true temperature measurements in low-conductivitymaterials (conductivity of material less than conductivity ofthermocouple wire) because of the heat sink effect of the bead.4.2.2 Recommendations

14、To minimize this effect, the junc-tion bead diameter should be no larger than 1.5 wire diametersfor butt-welded junctions and 2 wire diameters for other typesof welds.4.3 Thermocouple Wire in Isothermal Surface of Hot Junc-tion:4.3.1 GeneralBecause many materials have low thermalconductivity compare

15、d with those of thermocouple assemblies,it has been found that certain methods of installing sensors canproduce significant errors in internal temperature measurement1This practice is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and is the dire

16、ct responsibility ofSubcommittee E21.08 on Thermal Protection.Current edition approved Oct. 10, 1996. Published December 1996. Originallypublished as E 377 68. Last previous edition E 377 68 (1992).2ANSI MC96.1-1975. Temperature Measurement Thermocouples (SponsorISA).1Copyright ASTM International, 1

17、00 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(1-4).3Errors of several hundred degrees are possible unlessheat conduction away from the sensor hot junction, by thesensor materials, is minimized. Test results show that athermocouple having a sufficient length of b

18、are wire in theisothermal surface that includes the junction will minimizethese errors.4.3.2 RecommendationsIt is therefore recommended thatthe configuration of the thermocouple sensor be such that theleads perpendicular to the heat flow have a length equivalent toat least 25 wire diameters on both

19、sides of the junction in thesame isothermal surface that includes the hot junction.4.4 Disturbances in Vicinity of Thermocouple Sensor HotJunctions (2-4):4.4.1 GeneralIt is important that a minimum amount ofdisturbance be created in the material around the thermocouplejunction.4.4.2 RecommendationsT

20、he disturbed material removalarea (for placement of the thermocouple junction and leadwires) should be as small as possible. A maximum of No. 36AWG gage (0.127-mm or 0.005-in.) wire should be used forthe thermocouple wire from the junction and along the isother-mal surface which includes the junctio

21、n. Holes drilled forplacement of thermocouple wires should be 3 wire diameters orsmaller. It is recommended also that the difference in thermalconductivity between thermocouple assembly and the sur-rounding material be minimized by: (1) avoiding the use ofrelatively conductive (thermal) insulation (

22、such as ceramic andfiberglass types) around the portion of wire that is located inthe isothermal surface that includes the thermocouple junction,and (2) maintaining good thermal contact with the low-conductivity material by bonding the thermocouple to thespecimen (thus eliminating air pockets) with

23、the same orsimilar compound (such as an epoxy plastic) as that used tomake the specimen.5. Electrical Shorting by Conductive Char Layers5.1 GeneralThe char layer formed by most organic ma-terials becomes highly conductive (electrically) as pyrolysisprogresses. Care should be taken to avoid the possi

24、bility ofelectrical shorting of thermocouple lead wires not protected byproper insulation methods. Studies (1) have shown that short-ing can result in temperature errors of as much as 110 C (200F) in thermocouples which do not employ proper insulation ofthe lead wires.5.2 RecommendationsIt is recomm

25、ended that electricalshorting be avoided by using a ceramic coating or tubingaround the thermocouple lead wires. Two possible configura-tions are shown in Fig. 1 and Fig. 2. Use of either configurationshould provide accurate measurements in low-temperaturegradient fields (3). In that the wire temper

26、ature at the exit of theceramic cover in Fig. 2 may be substantially different from thatin the vicinity of the hot junction (3), the configuration in Fig.1 should be used in high-temperature gradient fields. Care mustbe taken to select an insulation that does not become electri-cally conductive at t

27、he temperatures being measured.6. Thermocouple Sensor Hot Junction Location Accuracy(1,2)6.1 GeneralThe thermocouple junction needs to be accu-rately located to assure reproducibility of data from specimento specimen and for accurate use of temperature data incomputer programs for determining materi

28、al thickness require-ments, etc.6.2 RecommendationsThe actual location of each thermo-couple should be verified by X ray prior to temperaturemeasurement experiments. Care should be taken to correct3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.NOTE 1I

29、f a number of thermocouples in depth are required, drill holes at varying locations on the circumference.NOTE 2Eliminate air pockets in junction plane by filling hole with same or similar compound as that used to make test specimen.NOTE 3This is a schematic representation and is not intended to be a

30、n engineering drawing.FIG. 1 Summary of Recommended Practices for Mounting ThermocouplesSchematic Representation for “One-Piece” CylindricalSpecimenE 3772X-ray measurements for parallax. Thermocouple junction,lead-wire location, and gas pockets are best checked by two Xrays taken in front and side v

31、iew.7. Summary of Recommendations (also summarized inFig. 1 and Fig. 2)7.1 Thermocouple Junction Bead DiameterMake beadsno larger than 1.5 wire diameters for butt-welded junctions and2 wire diameters for other types of welds.7.2 Thermocouple Lead Wire in Isothermal Surface thatIncludes the JunctionU

32、se a length of wire at least 25 wirediameters on both sides of the junction.7.3 Thermocouple Wire Diameter and Holes for WiresUse a maximum of No. 36 AWG gage wire and holes as smallas possible but no larger than 3 wire diameters.7.4 Thermal Conductance of Thermocouple AssemblyAvoid the use of relat

33、ively conductive insulation around wirein the isothermal surface that includes the junction. Bondthermocouple to the material with same or similar compound.7.5 Electric Shorting by CharUse a ceramic coating ortubing around the thermocouple lead wires.7.6 Thermocouple Sensor Hot Junction LocationAccu

34、racyLocate by X rays taken in front and side view.8. Keywords8.1 internal temperature; low-conductivity; thermocoupleREFERENCES(1) Dow, M. B., “Comparison of Measurements of Internal Temperaturesin Ablation Materials by Various Thermocouple Configurations.”NASA Technical Note D-2165, November, 1964.

35、(2) Moen, W. K., “Significance of Errors in High Temperature Measure-ment,” Society of Automotive Engineers, Inc., Paper No. 750F,presented at National Aeronautic and Space Engineering and Manu-facturing Meeting, Los Angeles, Calif., Sept. 23 to 27, 1963.(3) Beck, J. V., “Thermocouple Temperature Di

36、sturbances in Low Con-ductivity Materials,” Transactions, TASMA, ASME, Journal of HeatTransfer, Series C, Vol 84, 1962, pp. 124132.(4) Beck, J., V., “Study of Thermal Discontinuities and AssociatedTemperature Disturbances in a Solid Subject to a Surface Heat Flux,”Part IIIEffect of Sensors in Low Conductivity Material UponTemperature Distribution and Its Measurement, Technical ReportRAD-TR-9(7)-59-26. Contract Nos. AF 04(647)-305 and AF 04(647)-258.(5) Jakob, M., Heat Transfer, Vol II, John Wiley or through the ASTM website(www.astm.org).E 3774

copyright@ 2008-2019 麦多课文库(www.mydoc123.com)网站版权所有
备案/许可证编号:苏ICP备17064731号-1