Heat transfer to binary liquid mixtures in natural circulation evaporators

Experiments were made to investigate the effects of submergence, temperature difference and composition on the heat transfer rates to boiling water, isopropyl alcohol and their mixtures. The apparatus used was a natural circulation vertical tube evaporator, the test section being a copper tube 0.485" i.d., wall thickness 0.085" and heated length 47.75". The heating medium was steam contained in an annulus surrounding the test section. To ensure that the whole test section was used for boiling, the liquid was introduced to the evaporator at its local boiling temperature. Analysis of the results so obtained has indicated that within experimental limits nucleate boiling became less predominant with increasing temperature difference and decreasing submergence, being displaced by a convective-type heat transfer mechanism. [Continues.]