- Author
- Youngblood, W. W. | Schultz, W. | Barber, R.
- Title
- Solar collector Fluid Parameter Study.
- Coporate
- Wyle Laboratories, Huntsville, AL
- Sponsor
- National Bureau of Standards, Washington, DC Department of Energy, Washington, DC
- Report
- NBS GCR 79-184, October 1979, 130 p.
- Distribution
- Available from National Technical Information Service
- Contract
- NBSNB79SBCA0079 DOE-EG-77-C-0L-4050
- Keywords
- efficiency | flow rate | heat treasfer fluid | solar collector | thermal performance | solar collectors
- Abstract
- A series of instantaneous thermal performance tests were performed on four differently constructed, commercially available flat plate solar collectors with each of four commonly used heat transfer fluids. The tests were designed to illustrate the magnitude of fluid parameter effects on the thermal performance of flat plate solar collectors. The configurations were as follows: (1) water; (2) an ethylene glycol (Prestone 11) - water solution (50 percent by weight); (3) a silicone based heat transfer fluid (SYLTHERM 444); and (4) a synthetic hydrocarbon (Therminol 44). Each collector was tested with flow rates in the range of approximately 0.010 to 0.047 kg/sec per square meter (7 to 35 1bm/hr.ft2(superscript) of net aperture area. The efficiency of the heat collection process for each test was correlated with the heat transfer fluid flow rate. The ASHRAE 93-77 recommended flow rate of 0.02 kg/sec-m2 (superscript) (14.7 1bm/hr.ft2 (superscript) was used as a reference baseline. Results show a marked descrease in efficiency (5 to 8 percentage points) for all collectors tested when using the silicone oil and the synthetic hydrocarbon oil from the efficiency obtained when using water at the same flow rate. Decreases in efficiency of 2 to 4 percentage points were observed for all collectors tested when the Prestone-water solution was used compared to water at the same flow rate. The results indicate that a flat plate solar collector's thermal efficiency response to fluid parameter effects is a strong function of the absorber plate to fluid heat transfer path, and a weaker fuction of the collector's optical characteristics (i.e., ta).