Experimental and numerical study on thermal performance of an unvented Trombe wall associated with internal thermal fins

•A new unvented Trombe wall associated with thermal fins was studied.•Thermal fins increase the thermal efficiency of the unvented Trombe wall.•For a real scale building case, the optimum thermal fin height is 0.2 m.•Thermal fins reduce Trombe wall area necessary for passive heating in buildings.

To improve the energetic efficiency of an unvented Trombe wall and to maximize the heat transfer rate between this type of walls and the interior ambiance of the building, thermal innovation, consisting in adding vertical thermal fins to the internal Trombe wall surface, was studied.The thermal behavior of this new Trombe wall configuration was investigated in a Mediterranean region using a small scale test room, and compared to a classical Trombe wall.The results showed that thermal fins contribute to an internal room temperature rise and a decrease in the external Trombe wall temperature. This conducts to have a significant improvement of the thermal efficiency of this solar system compared to a similar context without thermal fins.As a result, the finned Trombe wall is more efficient than the classical one for high solar radiation up to 400 W/m2 and the maximum difference in the thermal efficiency between the two cases can reach 7% at a solar radiation intensity of up to 800 W/m2.Then, using the TRNSYS simulation software a new numerical model of a modified finned Trombe wall was developed and validated by the experimental results.The numerical study of the thermal fin height effect, on a real scale building, showed that the optimum thermal fin height was equal to 0.2 m and a 2 m2 finned unvented Trombe wall conducts to the same results, in term of annual heating loads, as a 4 m2 classical unvented Trombe wall.