MEASUREMENT OF SPECTRAL AND TOTAL EMITTANCE OF MATERIALS AND SURFACES UNDER SIMULATED SPACE CONDITIONS, JULY 1, 1959-JUNE 30, 1960

Technical Report · Wed Oct 31 00:00:00 EST 1962

OSTI ID:4775811

The first phase of an engineering program to measure thermal radiation characteristics of metal and coated metal surfaces under conditions of interest in space-craft applications was completed. Both spectral and total emittance measurements were made at 200 to 2000 deg F and at indicated pressures as low as 4 x 10/sup -9/ mm Hg. The change of emittance resulting from operation at elevated temperatures and high vacuum over periods of tlme up to 550 hours was also determined for some of the more promising materials. Total hemispherical emittance values above 0.7 were found for several coating materials in the temperature range of interest for application to the radiator-condensers of space- craft Rankine-cycle powerplants with liquid-metal working fluids. Coating materials which appear promising for this application include Cr black, Nb oxide, acetylene black, CuO, ZrC/sub 2/, BC, and crystalline B. Total emittance was determined for two smooth metal surfaces, one sandblasted metal surface, and sixteen coating materials. Spectral emittance was determined for three coatings and three smooth metal surfaces. The change of emittance with time under elevated temperature and high vacuum conditions was also determined for four of the coating materials and for the sandblasted metal surface. Total hemispherical emittance was determined by comparing the electrical power dissipation per unit area in a heated strip or tube specimen to the black body emissive power corresponding to measured specimen temperature. Spectral normal emittance was determined by comparing the spectral intensity issuing normal from the surface of an electrically heated specimen tube to the spectral intensity at the same wavelength of the essentially black body radiation at specimen temperature issuing from the tube interior through a small hole in the tube wall. Intensity ratios were obtained using a dual beam spectrophotometer viewing the specimen tube through a NaCl window in the vacuum chamber wall. Measurements were made over the wavelength range of 0.45 to 13.0 microns. Pt--90% Pt--10% Rh thermocouples, chromel-alumel thermocouples, and an optical pyrometer were used to measure specimen temperature. Several investigations were made to permit estimation of the accuracy of the emittance measurements. Errors caused by reflections from the chamber walls, local perturbations of specimen temperature, and heat conduction from the ends of the specimen were studied in regard to both total and spectral measurements. Effects of scattered radiation and imperfection of the black body hole'' radiation were also examined with reference to spectral measurements, as were thermocouple calibration drift problems associated with the total measurements. On the basis of these investigations it is believed that spectral emittances as reported are within +3% to -5% of the correct values, total emittances are within plus or minus 3% as measured on the spectral rig, and within plus or minus 5% as measured on the total emittance rig. (auth)

• Research Organization: Pratt and Whitney Aircraft Div., United Aircraft Corp., Hartford, Conn.
• DOE Contract Number: NASW-104
• NSA Number: NSA-16-032039
• OSTI ID: 4775811
• Report Number(s): PWA-1863
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-62
• Country of Publication: United States
• Language: English

Related Subjects

METALS, CERAMICS, AND OTHER MATERIALS
ACETYLENES
ALUMINUM ALLOYS
BORON
BORON CARBIDES
CHROMIUM ALLOYS
CHROMIUM COMPOUNDS
COATING
CONDENSERS
COPPER OXIDES
LIQUID METALS
MEASURED VALUES
METALS
NICKEL ALLOYS
NIOBIUM OXIDES
OPTICAL SYSTEMS
PHOTOMETRY
PLATINUM
PLATINUM ALLOYS
PRESSURE
REFLECTION
RHODIUM ALLOYS
SILICIDES
SODIUM CHLORIDES
SPACE
SPECTROMETERS
SURFACES
TEMPERATURE
THERMAL CONDUCTIVITY
THERMAL RADIATION
THERMOCOUPLES
USES
VACUUM
ZIRCONIUM OXIDES