Techniques for reducing thermal conduction and natural convection heat losses in annular receiver geometries

Conference · Sat Jan 01 00:00:00 EST 1977

OSTI ID:7293259

Ratzel, A. C.; Hickox, C. E.; Gartling, D. K.

An effective device for the collection of solar energy which has received widespread attention is the so called parabolic-cylindrical solar collector. In this design a circular receiver tube, with a suitable selective coating, is enclosed by a concentric glass envelope and situated along the focal line of a parabolic trough reflector. The heat transfer processes which occur in the annular space between the receiver tube and the glass envelope are important in determining the overall heat loss from the receiver tube. In typical high temperature receiver tube designs the rate of energy loss by combined thermal conduction and natural convection is of the same order of magnitude as that due to thermal radiation, and can amount to approximately 6 percent of the total rate at which energy is absorbed by the solar collector. The elimination of conduction and natural convection losses can significantly improve the performance of a large collector field. Several techniques useful for the reduction of energy loss by thermal conduction and natural convection are considered. The receiver configuration chosen for study is typical of those used in the Solar Total Energy System at Sandia Laboratories. The receiver tube has a ''black chrome'' selective coating and is 2.54 cm in outside diameter. The inside diameter of the glass envelope is approximately 4.4 cm. Typical operating temperatures of the receiver tube and glass envelope are approximately 300/sup 0/C and 100/sup 0/C, respectively.

• Research Organization: Sandia Labs., Albuquerque, N.Mex. (USA)
• DOE Contract Number: EY-76-C-04-0789
• OSTI ID: 7293259
• Report Number(s): SAND-77-0507C; CONF-771120-2
• Resource Relation: Conference: Winter annual meeting of the American Society of Mechanical Engineers, Atlanta, Georgia, USA, 27 Nov 1977
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
PARABOLIC COLLECTORS
HEAT LOSSES
OPTIMIZATION
CHROMIUM OXIDES
DESIGN
EFFICIENCY
MEDIUM VACUUM
NATURAL CONVECTION
PRESSURE DEPENDENCE
SIZE
SPECTRALLY SELECTIVE SURFACES
THERMAL CONDUCTION
CHALCOGENIDES
CHROMIUM COMPOUNDS
CONCENTRATING COLLECTORS
CONVECTION
ENERGY LOSSES
ENERGY TRANSFER
HEAT TRANSFER
OXIDES
OXYGEN COMPOUNDS
SOLAR ABSORBERS
SOLAR COLLECTORS
SURFACES
TRANSITION ELEMENT COMPOUNDS
141000* - Solar Collectors & Concentrators