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A number in parentheses indicates the year of last reapproval. For homogeneous opaque solid specimens of a representativethickness, thermal conductivity can be determined see Note1. NOTE 1—A body is considered homogeneous when the property to bemeasured is found to be independent of specimen dimensions. In addition, significantattention has been paid to ensure that the thermal resistance ofcontacting surfaces is minimized and reproducible.

The additional values are mathematical conversionsto inch-pound units that are provided for information only andare not considered standard. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.

Related Documents2. Current edition approved Aug. Published September Originallyapproved in Last previous edition approved in as E — United States Summary of Test Method4. Areproducible load is applied to the test stack by pneumatic orother means, to ensure that there is a reproducible contactresistance between the specimen and plate surfaces.

A guardsurrounds the test stack and is maintained at a uniform meantemperature of the two plates, in order to minimize lateral heatflow to and from the stack.

At steady state, the difference intemperature between the surfaces contacting the specimen ismeasured with temperature sensors embedded in the surfaces,together with the electrical output of the HFT.

This output voltage is proportional to the heat flow through the specimen,the HFT and the interfaces between the specimen and theapparatus. The proportionality is obtained through prior cali-bration of the system with specimens of known thermalresistance measured under the same conditions, such thatcontact resistance at the surfaces is made reproducible.

Significance and Use5. The relative position of the HFT to the specimen is notimportant it may be on the hot or cold side as the test methodFIG. It is also up to the designer whether tochoose heat flow upward or downward or horizontally, al-though downward heat flow in a vertical stack is the mostcommon one. In either case, meansmust be provided to ensure that the loading can be varied andset to certain values reproducibly. Other means of producing andmaintaining temperature may also be used as long as therequirements in 6.

The construction of the top plateis such as to ensure uniform heat distribution across its facecontacting the specimen 8. Itspurpose is to provide a highly conductive environment to thesecond temperature sensor 10 , to obtain an average tempera-ture of the surface. If the temperature sensor 10 is embeddedinto the face of the HFT, or other means are provided to definethe temperature of the surface facing the specimen, the use ofthe intermediate plate is not mandatory.

The level of output required sensitivity greatlydepends on the rest of the instrumentation used to read it. Theoverall performance of the HFTand its readout instrumentationshall be such as to meet the requirements in Section A small, generally unfilled, gap separates theguard from the stack.

For instruments limited to operate in theambient region, no guard is required but a draft shield isrecommended in place of it. NOTE 2—It is permissible to use thin layers of high-conductivity greaseor elastomeric material on the two surfaces of the specimen to reduce thethermal resistance of the interface and promote uniform thermal contactacross the interface area. NOTE 3—The cross-sectional area and the shape of the specimen maybe any, however, most commonly circular and rectangular cross sectionsare used.

Minimum size is dictated by the magnitude of the disturbancecaused by thermal sensors in relation to the overall flux distribution. Themost common sizes are 25 mm round or square to 50 mm round. NOTE 4—This requirement is also mandatory for testing materials thatsoften while heated.

Minimum loadshall not be below 0. Thermistors are normally present on more restricted allowabletemperature range of use. Sampling and Conditioning7. Test Specimen8. The recommended specimen configura-tion is a Fortesting specimens with thicknesses below 0.

Otherfrequently favored sizes are Adjust the guard heatertemperature Tg such that it is at approximately the average ofTuand Tl. Thisinformation is provided to assist the user in selecting optimumspecimen thickness for testing a material and in deciding whichcalibration specimens to use. The most commonly used calibration materials are the Pyrex and Pyroceram ,3Vespel4 polyimide and stainlesssteel all having well-established thermal conductivity behav-iors with temperature.

Thetemperature range listed for each reference material corre-sponds to the temperature range mentioned in each particularcited work, and in some cases exceeds the applicable tempera-ture range for this test method. The information was, however,considered useful for the general user, and for that reason itwas listed for the entire temperature range applicable to eachreference material.

EN 1254-3 PDF

Thermal Conductivity ASTM E1530



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ASTM E1530 - 19


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