Efforts are made to elucidate a three-dimensional (3D) computational work on laminar free/natural convection flows around the isothermally heated inclined hollow cylinder immersed in the quiescent ambient air negligible wall thickness. The thermofluidic characterization is performed by solving three-dimensional governing differential equations i.e. continuity, momentum, and energy equations over the following ranges of pertinent parameters: Rayleigh number, 104 ≤ Ra ≤ 108; cylindrical aspect ratio, 1 ≤ L/D ≤ 20; tube inclination, 0°≤θ ≤ 90°. Detailed behaviors of thermal and flow fields are delineated with the help of visualization technique like temperature contours and velocity vectors in order to identify the regions of low/high temperature gradient and fluid velocity. The influence of Ra, L/D, and θ on the local and average Nusselt number is predicted and it is seen that the average Nusselt number on outer and inner surface increases and decreases, respectively with the reduction in tube inclination for a particular Ra and L/D. A couple of correlation has been developed for the average Nusselt number on outer and inner surface of the hollow cylinder as a function of Ra, L/D, and θ based on the computed data points which would be helpful for various academic and industrial purposes.