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使用热流计测定稳态热传导特性的标准试验方法  
 【英文标准名称】  Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
 【原文标准名称】  使用热流计测定稳态热传导特性的标准试验方法
 【标准号】  ASTM C518-2010
 【标准状态】  Active
 【国别】  美国
 【发布日期】  2010
 【实施或试行日期】  
 【发布单位】  美国材料与试验协会(US-ASTM)
 【起草单位】  C16.30
 【标准类型】  (Test Method)
 【标准水平】  ()
 【中文主题词】  
 【英文主题词】  calibration; error analysis; heat flow meter apparatus; thermal resistance; heat flux; instrument verification; thermal conductivity; thermal testing
 【摘要】  

This test method provides a rapid means of determining the steady-state thermal transmission properties of thermal insulations and other materials with a high level of accuracy when the apparatus has been calibrated appropriately.

Proper calibration of the heat flow meter apparatus requires that it be calibrated using specimen(s) having thermal transmission properties determined previously by Test Methods C177, or C1114.

Note 18212;Calibration of the apparatus typically requires specimens that are similar to the types of materials, thermal conductances, thicknesses, mean temperatures, and temperature gradients as expected for the test specimens.

The thermal transmission properties of specimens of a given material or product may vary due to variability of the composition of the material; be affected by moisture or other conditions; change with time; change with mean temperature and temperature difference; and depend upon the prior thermal history. It must be recognized, therefore, that the selection of typical values of thermal transmission properties representative of a material in a particular application should be based on a consideration of these factors and will not apply necessarily without modification to all service conditions.

As an example, this test method provides that the thermal properties shall be obtained on specimens that do not contain any free moisture although in service such conditions may not be realized. Even more basic is the dependence of the thermal properties on variables, such as mean temperature and temperature difference. These dependencies should be measured or the test made at conditions typical of use.

Special care shall be taken in the measurement procedure for specimens exhibiting appreciable inhomogeneities, anisotropies, rigidity, or especially high or low resistance to heat flow (see Practice C1045). The use of a heat flow meter apparatus when there are thermal bridges present in the specimen may yield very unreliable results. If the thermal bridge is present and parallel to the heat flow the results obtained may well have no meaning. Special considerations also are necessary when the measurements are conducted at either high or low temperatures, in ambient pressures above or below atmospheric pressure, or in special ambient gases that are inert or hazardous.

The determination of the accuracy of the method for any given test is a function of the apparatus design, of the related instrumentation, and of the type of specimens under test (see Section 11), but this test method is capable of determining thermal transmission properties within x00B1; 2 % of those determined by Test Method C177 when the ambient temperature is near the mean temperature of the test (T (ambient) = T (mean) x00B1; 1x00B0;C), and in the range of 10 to 40x00B0;C. In all cases the accuracy of the heat flow meter apparatus can never be better than the accuracy of the primary standards used to calibrate the apparatus.

When this test method is to be used for certification testing of products, the apparatus shall have the capabilities required in A1.7 and one of the following procedures shall be followed:

The apparatus shall have its calibration checked within 24 h before or after a certification test using either secondary transfer standards traceable to, or...........

 【中国标准分类号】  A54
 【国际标准分类号】  91_120_10
 【页数】  15P.;A4
 【正文语种】  英语
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