Experimental investigation on heat loss of a fully open cylindrical cavity with different boundary conditions

► An experimental investigation on heat loss of a fully open cylindrical cavity. ► The heat loss characteristics with different boundary conditions were compared. ► The effect of inclination and heat flux on various types of heat losses. ► The empirical correlations for estimating the Nusselt numbers of heat losses. An experimental investigation using electrically heating method was carried out to explore the effects of surface boundary condition, tilt angle and heat flux on heat loss of a fully open cylindrical cavity. Three cases were examined: (i) only the bottom surface heated, (ii) only the side surface heated, and (iii) all surfaces heated. For all cases, the surfaces were heated with constant heat flux and the cavity rotates from 0° (the opening facing horizontally) to 90° (the opening facing vertically downwards) at intervals of 30° in addition to 45°. From the three cases, it is concluded that temperatures of bottom surface fluctuate in a small region, and side surface temperatures decrease with increasing position departure from bottom surface. The natural convection heat loss is sensitive to the tilt angle in comparison with the radiation and conduction heat losses. The heat loss characteristics are also dependent on the surface boundary conditions to some extent. When the total heat flux keeps constant, Nusselt numbers for determining the natural convection heat loss and the total heat loss reduce with increasing inclination. However, the inclination has little effect on the Nusselt number for determining the radiation heat loss. In addition, the empirical correlations of the natural convection, radiation and total heat loss Nusselt numbers versus the Grashof number, tilt angle and ambient temperature were proposed.