- Author
-
Kidd, C. T.
- Title
- Determination of the Uncertainty of Experimental Heat-Flux Calibrations. Final Report. October 1, 1981-September 20, 1982.
- Coporate
- Calspan Field Services, Inc.
- Sponsor
- Air Force Systems Command, Arnold AFS, TN
- Report
-
AEDC-TR-8313
Augsut 1983
64 p.
- Distribution
- AVAILABLE FROM National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161. Telephone: 1-800-553-6847 or 703-605-6000; Fax: 703-605-6900; Rush Service (Telephone Orders Only) 800-553-6847; Website: http://www.ntis.gov
- Keywords
-
heat flux
|
uncertainty
|
calorimeters
|
temperature measurements
- Identifiers
- slug calorimeter; transfer standard; standard deviation
- Abstract
- Several different sensors and/or techniques are utilized for the measurement of aerodynamic heating in the continuous wind tunnels of the von Karman Gas Dynamics Facility (VKF) at the Arnold Engineering Development Center (AEDC). These include discrete transdufers such as Gardon gages and Schmidt-Boelter gages, surface temperature sensors such as thin-film resistance thermometers and coaxial surface thermocouples, calorimetric devices such as thin-skin modets and individual slug calorimeters and infrared imaging systems for thermal mapping. Regardless of the sensor or technique employed for these measurements, the experimental calibration of the device should be traceable to common heat-flux standards. Heat-transfer rate or heat flux is perhaps the least tangible fundamental aerodynamic parameter measured in wind tunnel testing. Because of the elusive quality of the parameter, it is difficult to appraise the accuracy of heat-flux calibrations. Prior to October 1977, the National Bureau of Standards (NBS) neither maintained calibrated heat sources or heat-flux measurement standards, nor provided heat-flux transducer calibration services. Therefore, heat-flux calibration traceability to NBS standards was not possible. The heat-flux transducer designer usually inherited the added responsibility of establishing reliable calibration standards and calibration systems. With regard to the experimental calibration of transducers for wind tunnel heat-flux measurements, standards were established at the AEDC in 1963. These standards are slug-calorimeter transducers with fine-wire thermocouple temperature sensors. The experimental calibrations of all heat-flux transducers employed for wind tunnel measurements at the AEDC are traceable to the slug-calorimeter standards. Because of the excellent heat storage properties of the slug calorimeter, it takes an excessively long period of time for the calorimetric mass to return to ambient temperature after exposure to the heat source. Because of the amount of time involved and the data reduction technique (measurement of slope), the use of the slug-calorimeter standards on a routine basis is impractical. In order to alleviate this problem, the heat-flux calibration is transferred from the slug-calorimeter standards to transfer-standard transducers. Transfer standards used wit,h the radiant heat-flux calibration facJities at the AEDC are 1/4-in.-diam conventional Gardon gages and Schmidt-Boelter gages. The transfer standards are used to measure the heat-flux level from the heat source for routine calibrations. The basic principle of operation and physical configurations of the transfer standards and many transducers used in wind tunnel tests are identical. Therefore, a high degree of operational compatibility exists between the transfer standards and test transducers for routine calibration procedures.