Experimental Analysis of Flow Boiling in Horizontal Annulus—The Effect of Heat Flux on Bubble Size Distributions

Subcooled flow boiling was experimentally investigated in a horizontal annulus with temperature-controlled surface and transparent outer pipe facilitating visualization. Boiling occurs on copper tube diameter of 12 mm an 2 gap. Refrigerant R245fa is used as working fluid. The focus this study to explore the effect heat flux variation patterns at approximately constant inlet conditions fluid (fixed mass temperature). recorded by high-speed camera, images are analyzed neural network determine bubble size distributions their flux. experimental setup being part laboratory THELMA (Thermal Hydraulics Laboratory for Multiphase Applications) Reactor Engineering Division Jožef Stefan Institute, analysis methods measurement results presented discussed.