Calorimetric measurements of emittance of pipe surfaces: Influence of enclosure diameter, test pipe length and an argon atmosphere
Abstract
Additional results using a calorimetric technique for measuring the total hemispherical emittance of pipe surfaces from 400 to 600 K are described. Two different Pyrex pipe enclosures were used, one of 15 cm i.d. and the other of 30 cm i.d. An error analysis showed that the larger diameter Pyrex pipe should have a smaller error, but the difference was negligible for the 4.4-cm test pipe diameter used. Measurements on a short length of a previously-measured pipe agreed with earlier measurements, but only over the temperature range of the measurements. While the technique normally uses a vacuum to minimize nonradiative heat transfer, measurements were done successfully with an argon atmosphere in a closed system. A nickel-plated pipe, measured first in a vacuum and then in an argon atmosphere, allowed calculation of an effective convective heat-transfer coefficient for use with test pipes of unknown emittances. Measurements done with an atmosphere have larger uncertainties than those done in vacuum. Measurements using this technique agreed with measurements made using a reflectance technique. It is believed that within the range of temperatures measured, emittance measurements made using the calorimetric technique have a relative error of no more than 10% when done in vacuum.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- October 1981
- Bibcode:
- 1981STIN...8233675R
- Keywords:
-
- Calorimeters;
- Heat Measurement;
- Pipes (Tubes);
- Argon;
- Cylindrical Bodies;
- Diameters;
- Error Analysis;
- Glass;
- Length;
- Surface Temperature;
- Vacuum Apparatus;
- Fluid Mechanics and Heat Transfer