Experimental Studies of the Burnout under the Boiling : 1st Report, Transient Phenomena to Meltdown

Abstract

This paper deals with the burnout and melt down caused by step-input to a fine nichrome wire (0.2 mm diameter) which is vertically supported at the center of glass pipe (annulus) and cooled by natural circulation of water of 80°C subcooling at the atmospheric pressure. The results obtained are as follows : (1) For the transient nucleate boiling which exists between the biginning of boiling and the burnout point, the correlation between the heat flux and the superheating of surface temperature shows the same tendency, even higher than the burnout critical heat flux, as the results by Nukiyama or McAdams. (2) The time interval τ_B until the burnout occurs is given by the following equation : [numerical formula] where, C is constant, which is dependent on the annulus diameter, and q is heat flux (kcal/m²h). (3) The burnout critical heat flux which does not cause the burnout is 5.3×10⁵, 8.2 ×10⁵, 1.33×10⁶, 2.4×10⁶, and 2.4×10⁶ kcal/m²h, respectively, in the caee of 2, 3, 4, 6, and 8 mm of annulus diameter. (4) There are four different types of change in the temperature of nichrome wire until it is melted down after the burnout point.