Optical losses and heat transfer in an evacuated tubular absorber under 5x nonimaging concentration

Conference · Tue Jan 01 04:00:00 EST 1980 · Proc. Annu. Meet. - Am. Sect. Int. Sol. Energy Soc.; (United States)

OSTI ID:6549477

O'Gallagher, J; Hilgart, M; Snail, K; Winston, R

The use of nonimaging cusp type Compound Parabolic Concentrators (CPC's) of low concentration (1.1X-1.5X) with evacuated dewar type absorbers is well established. However, at higher concentration ratios (3X to 6X), because of the higher fluxes incident on the absorber and the relatively nonuniform flux distribution in these cases, the possibility that inadequate heat transfer would cause an overtemperature condition in the absorber has been a concern. The results of extensive operating experience with a 5.25X CPC are summarized. This collector used General Electric evacuated tubes and was built with Sheldahl silver foil mirrors. The system had an optical efficiecy (with an acrylic cover) of n/sub o/ = 63 /sup + -/ 1% relative to beam radiation and the best high temperature performance measured to date was an operating efficiency of 58 /sup + -/ 4% at an average fluid temperature of 220/sup 0/C above ambient. A detailed breakdown of the individual contributions to the optical losses shows that the observed efficiency is in very good agreement with material properties and a ray trace analysis. In general, heat transfer has not proved to be a serious problem although substantial temperature gradients have been measured in the absorber on the copper fin heat extraction fin. Results are reported.

• Research Organization: Univ. of Chicago, IL
• DOE Contract Number: AS02-76ET20236; AS02-78ER04657; AC02-80ER10558
• OSTI ID: 6549477
• Report Number(s): CONF-800604-P2
• Conference Information: Journal Name: Proc. Annu. Meet. - Am. Sect. Int. Sol. Energy Soc.; (United States) Journal Volume: 3.1
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
COMPOUND PARABOLIC CONCENTRATORS
CONCENTRATING COLLECTORS
CONCENTRATION RATIO
EFFICIENCY
ENERGY LOSSES
ENERGY TRANSFER
EQUIPMENT
EVACUATED COLLECTORS
EVACUATED TUBE COLLECTORS
HEAT LOSSES
HEAT TRANSFER
LOSSES
OPTICS
PARABOLIC COLLECTORS
PERFORMANCE
SOLAR ABSORBERS
SOLAR COLLECTORS
SOLAR CONCENTRATORS
SOLAR EQUIPMENT