Enhancement of Critical Heat Flux in Tight Rod Bundle with Wire Spacer

Abstract

The experiment of CHF (critical heat flux) was conducted for water boiling two-phase flow in three-pin tight rod bundle. The effects of with and without wire spacers and the pitch to diameter ratio p/d on CHF were investigated under the conditions of mass flux range 250-430 kg/(m 2 ·s), inlet temperature from 70 °C to 92 °C and the pressure of 0.1 MPa. The CHF was enhanced by wire spacers in comparison with the results of CHF without wire spacers. The CHF was enhanced by reducing the p/d from 1.18 to 1.10 under the same flow rate condition, although it did not change appreciably with the change of p/d under the same mass flux condition. Nomenclature  d Outer diameter of heater pin (m) D he Heated equivalent diameter (m) D hy Hydraulic diameter (m) d wire Wire diameter (m) G Mass flux (kg/m 2 ·s) H Axial pitch of wire spacer (m) L Heated length (m) P Pressure (MPa) p Pitch (m) q CHF Critical heat flux (kW/m 2) W Mass flow rate (kg/s) X Thermal equilibrium steam quality Z Distance from the upstream end of the heater pin to CHF position (m) Abbreviations CHF Critical heat flux LWR Light water reactor RMWR Reduced-moderation water reactor