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用瞬变零点量热器测量高能环境的超级传热速率的标准试验方法  
 【英文标准名称】  Standard Test Method for Measuring Extreme Heat-Transfer Rates from High-Energy Environments Using a Transient, Null-Point Calorimeter
 【原文标准名称】  用瞬变零点量热器测量高能环境的超级传热速率的标准试验方法
 【标准号】  ASTM E598-2008
 【标准状态】  Active
 【国别】  美国
 【发布日期】  2008
 【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】  E21.08
 【标准类型】  (Test Method)
 【标准水平】  ()
 【中文主题词】  
 【英文主题词】  calorimeter; convective; heat flux; heat flux gage; null-point; radiative; transient temperature; Calorimeter--aerospace applications; Convective energy; Extreme heat transfer rates; Heat flux; Heating tests--aerospace materials; Heat transfer; Trans
 【摘要】  

The purpose of this test method is to measure extremely high heat-transfer rates to a body immersed in either a static environment or in a high velocity fluid stream. This is usually accomplished while preserving the structural integrity of the measurement device for multiple exposures during the measurement period. Heat-transfer rates ranging up to 2.84 x00D7; 102 MW/m2 (2.5 x00D7; 104 Btu/ft2-sec) (7) have been measured using null-point calorimeters. Use of copper null-point calorimeters provides a measuring system with good response time and maximum run time to sensor burnout (or ablation). Null-point calorimeters are normally made with sensor body diameters of 2.36 mm (0.093 in.) press-fitted into the nose of an axisymmetric model.

Sources of error involving the null-point calorimeter in high heat-flux measurement applications are extensively discussed in Refs (3-7). In particular, it has been shown both analytically and experimentally that the thickness of the copper above the null-point cavity is critical. If the thickness is too great, the time response of the instrument will not be fast enough to pick up important flow characteristics. On the other hand, if the thickness is too small, the null-point calorimeter will indicate significantly larger (and time dependent) values than the input or incident heat flux. Therefore, all null-point calorimeters should be experimentally checked for proper time response and calibration before they are used. Although a calibration apparatus is not very difficult or expensive to fabricate, there is only one known system presently in existence (6 and 7). The design of null-point calorimeters can be accomplished from the data in this documentation. However, fabrication of these sensors is a difficult task. Since there is not presently a significant market for null-point calorimeters, commercial sources of these sensors are few. Fabrication details are generally regarded as proprietary information. Some users have developed methods to fabricate their own sensors (7). It is generally recommended that the customer should request the supplier to provide both transient experimental time response and calibration data with each null-point calorimeter. Otherwise, the end user cannot assume the sensor will give accurate results.

Interpretation of results from null-point calorimeters will, in general, be the same as for other heat-flux sensors operating on the semi-infinite solid principle such as coaxial surface thermocouples and platinum thin-film gages. That is, the effects of surface chemical reactions, gradients in the local flow and energy fields, thermal radiation, and model alignment relative to the flow field vector will produce the same qualitative results as would be experienced with other types of heat flux sensors. In addition, signal conditioning and data processing can significantly influence the interpretation of null-point calorimeter data.

1.1 This test method covers the measurement of the heat-transfer rate or the heat flux to the surface of a solid body (test sample) using the measured transient temperature rise of a thermocouple located at the null point of a calorimeter that is installed in the body and is configured to simulate a semi-infinite solid. By definition the null point is a unique position on the axial centerline of a disturbed body which experiences the same transient temperature history as that on the surface of a solid body in the absence of the physical disturbance (hole) for the same heat-flux input.

1.2 Null-point calorimeters have been used to measure high convective or radiant heat-transfer rates to bodies immersed in both flowing and static environme......

 【中国标准分类号】  A54
 【国际标准分类号】  17_200_10
 【页数】  10P.;A4
 【正文语种】  英语
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