ASTM E377-2008(2015) 1879 Standard Practice for Internal Temperature Measurements in Low-Conductivity Materials《测量低热导率材料材料内部温度的标准实践规程》.pdf
《ASTM E377-2008(2015) 1879 Standard Practice for Internal Temperature Measurements in Low-Conductivity Materials《测量低热导率材料材料内部温度的标准实践规程》.pdf》由会员分享,可在线阅读,更多相关《ASTM E377-2008(2015) 1879 Standard Practice for Internal Temperature Measurements in Low-Conductivity Materials《测量低热导率材料材料内部温度的标准实践规程》.pdf(4页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: E377 08 (Reapproved 2015)Standard Practice forInternal Temperature Measurements in Low-ConductivityMaterials1This standard is issued under the fixed designation E377; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 subje
3、ct 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 be r
4、egardedas 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 an
5、d 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 spacec
6、raft 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 isol
7、ate 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 with
8、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 wit
9、h theenvironment, and (4) proper use of instrumentation for readoutof thermocouple emf.NOTE 1Reader is referred to ASTM MNL 12 (1), and STP 492 (2), aswell as Kinzie, P.A., Thermocouple Temperature Measurement (3), forneeded information.3.2 The most important sources of error beyond the abovebasic a
10、reas are 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 virgi
11、n or charred 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 prese
12、nt that 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 measur
13、ements (See Refs (4-10).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 be
14、ad.4.2.2 RecommendationsTo 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.1This practice is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space T
15、echnology and is the direct responsibility ofSubcommittee E21.08 on Thermal Protection.Current edition approved May 1, 2015. Published June 2015. Originallyapproved in 1968. Last previous edition approved in 2008 as E377 08. DOI:10.1520/E0377-08R15.2ANSI MC96.1-1975. Temperature Measurement Thermoco
16、uples (SponsorISA).Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.3 Thermocouple Wire in Isothermal Surface of Hot Junc-tion:4.3.1 GeneralBecause many materials have low thermalconductivity compared with those of thermocouple assem
17、blies,it has been found that certain methods of installing sensors canproduce significant errors in internal temperature measurement(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 t
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