Nucleate boiling in drag-reducing polymer solutions

Nucleate boiling curves and bubble dynamics have been experimentally measured in both pure water and aqueous solutions of drag-reducing polymers. The boiling curves have been measured using an electrically heated platinum wire submerged in a saturated pool of liquid at atmospheric pressure. Polymer concentrations corresponding to relative viscosities of 1.01, 1.04, 1.08, 1.16, and 1.32 have been tested. The observed changes in the nucleate boiling curves for polymer solutions are in qualitative agreement with those predicted based only on how the polymers change the solution viscosity. Drag reduction effects appear to be unimportant. The bubble dynamics have been measured using a high speed movie camera. For pure water, the average number density of active nucleation sites has been found to increase linearly with the boiling heat flux. In addition, the frequency distribution of bubble departure diameters has been found to be well represented by an asymptotic expansion of the normal frequency function. These data have been used to determine the relative contributions to the boiling heat flux of latent heat transport by vapor bubbles, natural convection heat transfer, and enhanced convection heat transfer. For drag-reducing polymer solutions, the bubble dynamics are significantly different from those observed with pure water. Each specific type of polymer changes the nucleation characteristics of the heated surface, and therefore, generalizations cannot be made as to how drag-reducing polymers as a group affect the bubble dynamics