1991 Volume 8 Issue 2 Pages 103-110
An experimental study has been performed to investigate the heat-transfer characteristics in a concentric-tube closed thermosyphon in which boiling and free convection take place. The outer tube of the thermosyphon used in this study was 100mm in diameter with 3420mm in height, which consisted of both some individual electrical heating copper tubes of 330mm in length and lucite tubes of 60mm in length. On the other hand, inner copper tubes of 41.3mm and 66.6mm in diameter with 3270mm in length were adopted. Experiments were carried out under the constant wall surface temperature conditions and refrigerant R-11 was utilized as a testing fluid. Out of a number of possible controlling valiables, the effect of the heat flux, the void fraction, the ratio of heating length to the total test section length, and the diametric ratio of the concentric tube on the heat-transfer performance were determined.
