Experimental study of critical heat flux in a two‐phase open concentric‐tube thermosyphon

Abstract

An experimental study was made to elucidate critical heat flux (CHF) characteristics in a two-phase concentric-tube thermosyphon. The experiment was performed by using saturated water, ethanol, and R113 over the experimental range of configuration: inner diameter of heated outer tube Di = 17 mm, outer diameter of unheated inner tube do = 3 to 15 mm and heated tube length L = 500 and 1000 mm. The experiment shows that the CHF is enhanced by an increase in the inner tube diameter, and that the CHF decreases beyond a certain diameter of the inner tube. There is an optimum diameter for the inner tube that maximizes the CHF, for each tube length and test liquid. The CHF maximum is about four or six times as large as that without an inner tube. For a large inner tube, the CHF characteristic is similar to that for natural convective boiling in a vertical annular tube. © 1998 Scripta Technica. Heat Trans Jpn Res, 26(5): 319–331, 1997