Interfacial Phenomena in Change-of-Phase Heat Transfer: Low Concentration Polymer Solutions

Abstract

Interferometry was used to measure in situ the thickness profiles of evaporating thin films as a function of heat flux for low concentration polystyrenel/cyclohexane solutions. Evaporative heat flow rates per unit width of contact line were calculated based on polynomial fits of interference data, combined with a fluid flow model. Temperature profiles obtained from thermocouple measurements were employed in evaluating macroscopic interline region heat sink capacities using a one-dimensional heat conduction model. Reasonable agreement between evaporative heat fluxes derived from both methods was established. Pure solvent integral heat fluxes were not significantly altered through polymer addition. Fluid flow toward the triple interline to replace that which evaporated resulted in an apparent non-equilibrium phase separation of concentrated polymer solution from the bulk phase; the separation increased with increasing polymer molecular weight and concentration. A substantial rise in the reflectivity beyond the first interference fringe indicated the possible deposit of an ultra-thin polymer or polymer solution film.

Presented at the 42nd Annual Meeting in Anahelm, California May 11–14, 1987

Notes

Presented at the 42nd Annual Meeting in Anahelm, California May 11–14, 1987