Film Boiling around Vertical Cylinders with End Surfaces of Various Configurations (1st Report: Film Boiling Heat Transfer)

In order to clarify the effect of bottom and top configurations on pool film boiling heat transfer from a vertical cylinder with a length comparable to the diameter, five kinds of silver cylinder with flat, hemispherical and conical end surfaces were tested by quenching in saturated and subcooled water. For saturated water, the wall heat flux averaged over the total surface of a finite-length cylinder takes a higher value for the cylinder with a conical bottom than those for the other four types as the wall superheat decreases. For highly subcooled bulk water, the average wall heat flux for the cylinder with a flat bottom becomes larger than those for the cylinder with hemispherical and conical bottoms. This is attributed that the cylinder with a flat bottom has quite a thin vapor film at the lower end of the vertical finite-length cylinder due to the edge effect