Natural convection characteristics of flat plate collectors. Progress report

Technical Report · Thu Sep 01 04:00:00 EDT 1977

DOI:https://doi.org/10.2172/5313804· OSTI ID:5313804

Randall, K R; Wl-Wakil, M M; Mitchell, J W

The results of an experimental investigation into the convective heat losses in large aspect ratio flat-plate solar collectors are described. An experimental study has been undertaken on a specially designed test cell using a 3 inch Mach-Zehnder interferometer. Air at atmospheric pressure was used as the heat-transfer fluid. The experimental results include interferograms which show the thermal boundary layer formations and the temperature profiles. Local temperature profiles have been analyzed through the use of an optical comparator to determine local Nusselt number profiles, which have, in turn, been integrated to give average heat-transfer results. Angles of inclination from the horizontal of 45, 60, 75 and 90 degrees have been investigated. Aspect ratios from 9 to 36 were examined over a Rayleigh number range of 4,000 to 310,000. Finally, heat-transfer correlations have been developed for the prediction of local Nusselt numbers in the starting and departure corners and for the average heat-transfer results as a function of collector tilt angle.

• Research Organization: Wisconsin Univ., Madison (USA). Engineering Experiment Station
• OSTI ID: 5313804
• Report Number(s): COO/2971-1
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
AIR
ASPECT RATIO
CONVECTION
ENERGY LOSSES
ENERGY TRANSFER
FLAT PLATE COLLECTORS
FLUIDS
GASES
HEAT LOSSES
HEAT TRANSFER
INTERFEROMETRY
NATURAL CONVECTION
ORIENTATION
SOLAR AIR HEATERS
SOLAR COLLECTORS
TEMPERATURE MEASUREMENT
WORKING FLUIDS