Effects of Absorber Geometric Pattern on the Thermal Performance of a Solar Water Heating System

The effects of a multichannel absorber geometric pattern on thermal performance of a solar water heating system was investigated. Research has shown that the water flow pattern inside the absorber is determined by the... [ view full abstract ]

The effects of a multichannel absorber geometric pattern on thermal performance of a solar water heating system was investigated. Research has shown that the water flow pattern inside the absorber is determined by the geometric pattern of the absorber and has a significant influence on the thermal performance of solar thermal collectors. In order to determine the effect of geometric patterns, a number of multichannel layout arrangement were investigated through CFD simulations. A more effective layout (mosaic arrangement) of the multichannels was identified. In order to investigate the influence of the flow distribution through the mosaic absorber, two collector designs that differ in layout of multichannels were investigated. The first pattern was based on parallel arrangement of the multichannels in which water flows following the traditional serpentine pattern. The second pattern was a mosaic arrangement of the multichannels, in which water flows from one end of the collector towards the center until it eventually flows out near the center of the collector. The effects of these absorber geometric patterns on the thermal efficiency and stratification of water in an aluminum storage tank were investigated. The overall efficiency was found to be 56% for the serpentine multichannel collector, while that for the mosaic arrangement was found to be 65%. The solar fraction averaged 0.58 and 0.62 for the serpentine multichannel collector and the mosaic multichannel collector respectively. The maximum useful volume from the 100-litre storage system was found to be 75 litres for both collector designs. The average heat loss coefficient of the storage tank was found to be 0.6 W/K. The self-discharge time of the system was found to be 23 hours. These results show that the mosaic multichannel arrangement is more efficient. Hence, it can be concluded that the absorber geometric pattern has an influence not only on the collector efficiency but also on hot water storage system.  

Acknowledgements This research was made possible by a NPRP award NPRP 5-161-2-053 from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors.