Subcooled pool film boiling heat transfer from small horizontal cylinders at near-critical pressures

Experimental results for subcooled pool film boiling on small horizontal cylinders at near-critical pressures are presented. Experiments were performed with CO2 was the test liquid and platinum wires (25.4, 76.2 and 100 μm diameter, D) as the test heaters. The pressure (P), liquid subcooling (ΔTsub) and bulk liquid temperature (Tb) were varied parametrically. For the range of parameters investigated, the heat transfer coefficient (h) was found to be proportional to D−0.5. Because the dependence of h on D varies, a criterion has been developed to predict a priori what this dependence would be any given situation. Subcooled pool film boiling heat transfer coefficient data have been correlated. The correlation developed predicts almost all the experimental data from the current study to within ±10%. The strength of the new correlation is that it is applicable to a much wider range of experimental conditions (including level of gravity) and fluids as demonstrated by the fact that it predicts all of the data reported in the literature to within ±20%. Visual observations during experiments showed that the transitions in film boiling patterns are a function of the dimensionless cylinder diameter.