Experimental investigation on critical heat flux in vertical tubes

摘要

An experimental study on critical heat flux of forced convection boiling in uniformly heated vertical tubes was performed in the KRISTA test facility at the Institute for Applied Thermo-and Fluid dynamics karlsrule. Research Center, using Freon-12 as the working fluid. Critical heat flux q_c was measured in a 16 mm and a 2 mm diameter circular tubes. The effect of pressure, steam quality and mass velocity on CHF has been investigated. The results obtained were found to be essentially consistent in trend with the CHF data measured by other authors. However, at lower pressure and mass velocity an anomalous phenomenon appeared: CHF decreased with decreasing inlet quality X_in in 2 mm diameter tube. The effect of pressure on CHF was complex. It was coupled with mass velocity and steam quality. At high mass velocity an inversion point was found out.