Reliability testing of active SDHW components. Part II. Results of collector scaling tests and the effect on thermal performance from scale build-up
The objective of this work was to determine how much scale accumulates in a flat-plate collector caused by repeated filling and draining. Laboratory testing of solar domestic hot water system components in FY 1983 showed that a significant amount of scale accumulated on draindown (drainout) valves, air vents, vacuum breakers, check valves subject to periodic draining on one side (such as when used as an isolation valve), and tempering valves. In FY 1984, we tested a flat-plate collector to measure the degree of scale accumulation caused by evaporation of water. Testing over a period of one year and 9733 cycles caused a 7% decrease in collector volume because of scale, which is equivalent to uniform scaling of 0.25 mm. A 1-mm scaling thickness would decrease the heat removal factor by 6% of increase the absorber plate temperature and overall heat loss factor U/sub L/ by 5/sup 0/C and 2%, respectively. This would result in a 13% reduction in the amount of energy collected. Homeowners in geographical areas where the water has a high potential for scaling should not use direct solar energy systems that use conventional flat-plate collectors unless they treat the water before it enters the system.
- Research Organization:
- Solar Energy Research Inst. (SERI), Golden, CO (United States)
- DOE Contract Number:
- AC02-83CH10093
- OSTI ID:
- 6228303
- Report Number(s):
- SERI/TR-253-2604; ON: DE86004419
- Country of Publication:
- United States
- Language:
- English
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