An experimental study is conducted to investigate the effects of inclination angle on the natural convection of water inside a cubic cavity with the side size of 20 cm × 10 cm × 10 cm. One of the surfaces of the cavity is kept in cold temperature and another one (opposite side) in hot temperature while the other four surfaces are insulated. Distilled water is used as the heat transfer fluid. The required volume of water for each test was 2000 mL. The heat transfer in the cavity is investigated in three inclination angles with respect to the horizontal position including 0, 45 and 90. The Nusselt number results are presented for the different angles of inclination and Rayleigh number. The results reveal that the maximum Nusselt number is dependent on inclination angle of the cavity. Also, it is found that the inclination angle of 90 results in the maximum Nusselt number for different Rayleigh numbers. The results reveal that by increasing the inclination angle from 0 to 90, the heat transfer coefficient increases and consequently heat transfer increases, especially in the lower Rayleigh number. A significant change in the Nusselt number was not observed with the change in the slope of the container at high Rayleigh numbers.

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