Transmittance-absorptance product for concentric tubular collector elements, developed for the three-dimensional case
Conference
·
· Proc. Annu. Meet. - Am. Sect. Int. Sol. Energy Soc.; (United States)
OSTI ID:6547929
A method is presented for calculating the overall transmittance (tau/sub e/) and the transmittance-absorptance product (tau..cap alpha..) for an absorber of circular cross section mounted concentrically within a tubular glass envelope, also of circular cross section, for the general condition in which the direct incident rays lie in planes not perpendicular to the long tubular axis. Assumptions are that the tube is very long in comparison with its diameter, that the space between envelope and absorber is evacuated, that the absorbing surface is specular and of constant absorptivity regardless of incident angle, and that the incident radiation is collimated. Account is taken for absorption of energy within the envelope. Results in chart form display the variation in the product with incident angle (the angle by which incident rays differ from perpendicular to the long tubular axis), with the envelope's refractive index, with the absorptivity of the receiving surface, and with the ratio of absorber to envelope diameter. These findings indicate that the tau..cap alpha.. product falls off only slightly as the angle of incidence varies from zero to moderate (up to 40/sup 0/) values.
- Research Organization:
- Montana State Univ., Bozeman
- OSTI ID:
- 6547929
- 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
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