CRITICAL HEAT-FLUX MULTIPLIER OF SUBCOOLED FLOW BOILING FOR NONUNIFORM HEATING CONDITIONS IN A SWIRL TUBE

In this paper, two factors were proposed to examine the relation between the critical heat flux (CHF) enhancement in swirl tubes and the intensity of non-uniformity under non-uniform heating conditions. One is a CHF multiplier Phi defined as a ratio of the peak heat flux at the CHF (q(c,H)) under non-uniform heating conditions to the CHF under uniform heating conditions. The other is a non-uniformity factor (NF), which represents the intensity of non-uniformity. The NF was tentatively defined as the ratio of q(c,H) to the average flux at the cooled wall. The heat flux distributions at the cooled wall for the beam irradiated test data from J.A. Koski and C.D. Croessman (ASME Paper 88-WA/NE-3, 1988), S.L. Milora, S.K. Combs, and C.A. Foster (Nucl. Eng. Des. Fusion 3 (1986) 301-308), J. Schlosser, A. Cardella, P. Massmann, P. Chappuis, H.D. Falter, P. Deschamps, and G.H. Deschamps (7th Proc. of Nuclear Thermal Hydraulics, ANS Winter Meet., 1991, pp. 26-31), and J. Schlosser and J. Boscary (3rd Specialists' Workshop on High Heat Flux Component Cooling, Cadarache, September 1993) were estimated by solving an unsteady heat conduction equation. The relation between Phi and the NF for these data was examined. It was confirmed that Phi increased with the increase in the NF and the beam irradiated data could mostly be predicted using the NF. The effects of the geometric parameters of a rectangular block, which mounted the cooling channel, on the NF were also discussed.