Velocity,subcooling and surface effects in the departure from nucleate boiling of organic binaries

The forced-convection loop at the University of Toronto was used to determine DNB heat fluxes for the full range of variation in composition of the binary systems acetone-toluene and benzene-toluene, over the velocity range 1.09-4.36 metre/sec. and the subcooling range 10-50°C. Special attention was given to the precise location of the DNB point relative to the maximum (critical) heat flux. The variation of the DNB heat flux with composition was found to be complex, but an empirical graphical correlation was obtained for each system, correlating DNB heal flux with composition, velocity and subcooling. A limited study of the effect of degree of surface roughness pointed towards an effect on DNB which varied with the degree of subcooling, but which was independent of the coolant velocity.