Nucleate Boiling in Drag-Reducing Polymer Solutions

Abstract

This paper summarizes the important findings of all our previous work concerning nucleate boiling in drag-reducing polymer solutions. Nucleate boiling curves are presented for aqueous solutions of three different molecular weight grades of hydroxyethyl cellulose and three different types of polyacrylamide. The boiling curves have been measured using an electrically heated platinum wire submerged in a saturated pool of liquid at atmospheric pressure. When compared to the boiling curve of the pure solvent, in this case water, all of the polymer solution boiling curves showed higher temperature differences as the polymer solution viscosity increased. These results differ from those reported by earlier investigators for pool boiling of dilute polymer solutions on heated flat plates.

In addition, for one of the hydroxyethyl cellulose solutions and for one of the polyacrylamide solutions, the boiling bubble dynamics along with the entire heated length of the wire have been photographed using a high speed movie camera. When compared with the pure solvent boiling at the same heat flux, both polymer solutions showed a considerable decrease in the number density of active nucleation sites, slightly smaller average bubble departure diameters, and slightly higher average bubble departure frequencies. The decrease in the active nucleation site density for the polymer solutions is primarily responsible for the higher temperature differences needed to maintain the same boiling heat flux in our experiments.