Gas heat conduction in an evacuated tube solar collector
- Ludwig-Maximilians-Universitaet Muenchen (Germany)
- ZAE Bayern, Muenchen (Germany)
We investigated experimentally the pressure dependency of the gas heat conduction in an evacuated plate-in-tube solar collector. A stationary heat loss experiment was built up with an electrically heated real-size collector model. The gas pressure was varied from 10{sup -3} to 10{sup 4} Pa, the temperatures of the absorber and the casing were held at 150{degree}C (electrical heaters) and 30{degree}C (water cooling), respectively. Losses by radiation and solid conduction were determined experimentally at pressures below 0.1 Pa. At higher pressures these background losses were subtracted from the total heat losses, to receive the heat losses by gas heat conduction. The experimental results were compared with approximate theoretical models. The onset of convection is in agreement with the usual theories for parallel plates taking the largest distance between the absorber and the gas tube as the plate distance. As a first approximation the pressure dependency of the gas heat conduction is described by the usual theory for parallel plates, taking the smallest distance between the absorber and the glass tube as the plate distance. 11 refs., 3 figs.
- OSTI ID:
- 501959
- Report Number(s):
- CONF-950901-; ISSN 0038-092X; TRN: 97:004299-008
- Journal Information:
- Solar Energy, Vol. 58, Issue 4-6; Conference: International Solar Energy Society (ISES) solar world congress: in search of the sun, Harare (Zimbabwe), 9-16 Sep 1995; Other Information: PBD: Oct-Dec 1996
- Country of Publication:
- United States
- Language:
- English
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Analysis of gas heat conduction in evacuated tube solar collectors
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