Performance and modeling of an evacuated-tube, integral-collector-storage solar water heater
- Colorado State Univ., Fort Collins, CO (United States). Solar Energy Applications Lab.
- Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Mechanical Engineering
An experimental study of an evacuated-tube, integral collector-storage water heater was conducted in an indoor solar simulator. Useful collected energy, radiation-induced stratification and draw-induced mixing are characterized in 8 trials in which test duration, initial tank water temperature, flow rate during withdrawal of heated water from the collector, withdrawal pattern and reflectance of the back plane were varied. All tests were performed at nominal irradiance of 900 W/m{sup 2}, normal incidence, and collector slope of 45 degrees. The capability of the TRNSYS integral collector storage model to predict performance for operating conditions for which data are assumed to be unavailable is assessed. Using data from one experimental trial, optical efficiency ({tau}{alpha}) of the collector is determined by matching predicted useful energy gain to measured gain. Effectiveness of the calibrated model is evaluated by comparing predicted gains to measured values obtained in the remaining 7 trials. For 5 of 7 trials, predicted performance is within 9% of measured performance and less than experimental error. For the other 2 trials, predicted performance is within 15% of measured performance. The higher discrepancies may be partially due to experimental conditions not modelled such as heating of the piping connecting the collector to the test facility and inadequate characterization of back-plane reflectivity. The model does not predict radiation-induced stratification. Although the effect of mixing during draws can be approximated by specifying the number of fully mixed volume segments in the tanks, selection of number of nodes requires knowledge of the behavior of the system. The number of nodes selected has minimal impact on total energy gain, but does affect the temperature of water delivered to the load.
- OSTI ID:
- 116243
- Report Number(s):
- CONF-950336-; ISBN 0-7918-1300-2; TRN: IM9545%%210
- Resource Relation:
- Conference: American Society of Mechanical Engineers/Japanese Society of Mechanical Engineers/Japan Solar Energy Society international solar energy conference, Lahaina, HI (United States), 19-24 Mar 1995; Other Information: PBD: 1995; Related Information: Is Part Of Solar engineering 1995: Proceedings. Volume 2; Stine, W.B. [ed.] [California Polytechnic Univ., Pomona, CA (United States)]; Tanaka, Tadayoshi [ed.] [Electrotechnical Lab., Ibaraki (Japan)]; Claridge, D.E. [ed.] [Texas A and M Univ., College Station, TX (United States)]; PB: 582 p.
- Country of Publication:
- United States
- Language:
- English
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