Thermal performance of a novel water blind-Trombe wall system: A comparative experimental investigation

Abstract

A traditional Trombe wall suffers from undesired heat gains, single service function, and poor aesthetic appearance, and these drawbacks act as a barrier to its widespread application. This study introduced a newly designed Trombe wall, which neatly incorporated a water-flowing channel and venetian blind (named WBTW). The WBTW can efficiently provide space heating, domestic hot water, and simultaneously act as a shade for reducing cooling load in hot summer. To examine the operating performance of the WBTW under different modes, long-term comparative experiments between a room with the WBTW and that with a flat plate solar water collector (SCCW) and one with a conventional south wall were conducted under realistic climate conditions. Through the test under hot water mode, it was observed that the average thermal efficiency of the WBTW reached 52.8% throughout different seasons, which was 8.2% higher than that of the SCCW. Furthermore, in summer the combined use of external circulation ventilation and water circulation for the WBTW was suggested to avoid overheating phenomenon although that was at the sacrifice of hot water temperature. Space heating experiments showed that the coefficient of thermal comfort enhancement was 0.744 for the room with WBTW under linked air–water heating mode, while that was only 0.155 under stand-alone air heating mode. Finally, based on the validated theoretical model of the WBTW system, a sensitivity analysis of operating and structural parameters was conducted. As to the influence on the annual heat gains of the WBTW system, the order was blinds angle (a) > the ratio of blind spacing to width (r) > air inlet velocity (v) > water mass flow rate (w) > air channel depth (d). The optimum level combination was a = 30°, r = 1, v = 0.4 m/s, w = 0.08 kg/s and d = 0.3 m.