Natural convection is investigated experimentally in an inclined open cylindrical passege heated under constant heat flux condition to study the effect of angle of inclination and heat flux on heat transfer. Heat transfer results are given for inclination angles of 0o (horizontal), 30o , 60o and 90o (vertical).Using cylinder diameter of 4.8 cm, cylinder length 50 cm and heat flux from 70 W/m2 to 600 W/m2 . Empirical correlations are given for the average Nusselt number as a function of the
Rayleigh number. The results show that the local and average Nusselt number increase as the heat flux increase and when angle of inclination changed from 0o (horizontal) to 90o
(vertical). An empirical correlations of average Nusselt number as a function of Rayleigh number were obtained.