Enhanced heat transfer in confined pool boiling

We report the results of an experimental investigation of the heat transfer during nucleate boiling on a spatially confined boiling surface. The heat flux as a function of the boiling surface temperature was measured in pool boiling pots with diameters ranging from 15 mm down to 4.5 mm. It was found that a reduction of the pool diameter leads to an enhancement of the nucleate boiling heat flux for most of the boiling curve. Our experimental results indicate that this enhancement is not affected by the depth of the boiling pot, the material of the bounding wall, or the diameter of the inlet water supply. High-speed camera imaging shows that the heat transfer enhancement for the spatially confined pool boiling occurs in conjunction with a stable circulating flow, which is in contrast to the chaotic and mainly upward motion for boiling in larger pool diameters. An explanation for the enhancement of the heat transfer and the associated change in flow pattern is found in the singularisation of the nucleate boiling process.