Development of a high performance air heater through use of an evacuated tube cover design. Final report

Technical Report · Thu Jan 01 04:00:00 EST 1981

DOI:https://doi.org/10.2172/6515846· OSTI ID:6515846

Jones, D E; Shaw, L E; Loef, G O.G.

Work leading to the development of a high performance air heater through use of an evacuated tube cover design is detailed. Work consisted of a literature survey, fabrication of the tubes, solar transmittance tests, thermal conductance tests, collector design, prototype construction; prototype testing, and finally performance and cost evaluation. Two types of evacuated tubes were manufactured, clear tubes and tubes with an infrared reflective coating. The tubes were arranged parallel in a close packed flat array to form a transparent cover for the collector. The array transmittance of clear tubes is similar to that of two flat sheets of low absorptance glass. The coated tube array had substantially reduced transmittance. Thermal conductance tests indicated that the tube arrays perform similar to two flat sheets of glass with an evacuated space. Convection off the lower and upper surface of the tube arrays was enhanced by the larger surface area which somewhat offset the advantage of the vacuum. Two prototype collectors were designed, built, and tested: (1) clear tube array over a selective surface; (2) coated tube array over a non-selective surface. The collectors were tested side by side with two baseline collectors, a selective surface collector without a tube array and a standard Solaron collector. Test results indicate the tube collector performs better at higher temperatures than either baseline or the coated tube collector, but the performance increase is not outstanding. Inclusion of the evacuated tube cover concept is probably not cost competitive with other collectors in either the high or low temperature range.

• Research Organization: Solaron Corp., Englewood, CO (USA)
• DOE Contract Number: AC04-78CS34193
• OSTI ID: 6515846
• Report Number(s): DOE/CS/34193-T1
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
AIR HEATERS
COATINGS
COMPARATIVE EVALUATIONS
CONVECTION
COST
DESIGN
EFFICIENCY
EQUIPMENT
EVACUATED COLLECTORS
EVACUATED TUBE COLLECTORS
FABRICATION
FLUORESCENT LAMPS
HEATERS
LIGHT BULBS
PERFORMANCE TESTING
PHYSICAL PROPERTIES
REFLECTIVE COATINGS
SOLAR AIR HEATERS
SOLAR COLLECTORS
SOLAR EQUIPMENT
TESTING
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES