Performance evaluation of delta-nabla channel configuration in a solar absorber with thermal energy storage. (15th August 2023)

• Record Type: Journal Article
• Authors: Khan, Farooq; Cheema, Taqi Ahmad; Tariq, Muhammad Hasnain; Abbas, Ahmad; Amber, Khuram Pervez; Park, Cheol Woo
• Is Part Of: Journal of energy storage. Volume 65(2023)
• Publication Date: 2023-08-15
• Subjects: Solar water absorber -- Thermal performance -- Thermal energy storage -- Domestic water heating system -- Phase change material; Energy storage -- Periodicals; Energy storage -- Research -- Periodicals; 621.3126
• DOI: 10.1016/j.est.2023.107355
• Languages: English
• ISSNs: 2352-152X

Abstract

Abstract: A novel configuration of solar absorber containing water channels of triangular cross-section in a delta-nabla arrangement, has been experimentally investigated. Traditionally, the triangular channeled solar absorbers are in use for space heating, but their effectiveness in solar water heating systems is yet to be explored. In addition to the performance investigation of the absorber, the effect of an integrated phase change material (PCM) based thermal energy storage (TES) has also been examined under solar and off-solar conditions. The highest temperature of 80 °C is obtained on the right side of the absorber containing hot water outlet in contrast to the left side where the cold-water inlet is located. Moreover, the average temperature gradient exists along the surface normal from the channel contours to the outside glazing. Integration of paraffin-based TES provides 62 L of water above 30 °C during off solar conditions. The efficiency of TES increases with smaller delays after charging and for higher flow rates because of reduced heat losses from the storage to the atmosphere. A delta-nabla configuration comparison with a conventional flat plate type solar absorber shows a prominent improvement in the overall performance. Highlights: Channels of solar absorber in a delta-nabla assembly are experimentally tested. Proposed absorber is capable of storing sensible energy with 21 L of water. Up to 80 °C temperature of water is obtained on the right side of the absorber. Higher flow rate drives more heat away from the channels of the absorber. Adding 75 % paraffin oil in paraffin wax reduces its melting point by 17-23 °C. Lags in discharge reduce exiting temperature, power, and efficiency of storage.