An experimental investigation of nucleate pool boiling in aqueous solutions of a polymer

Abstract

Nucleate boiling characteristics of aqueous solutions of hydroxyl ethyl cellulose (HEC QP-300; M ~ 600 kg/mol) in different concentrations (1.0 × 10 -9 ≤ C ≤ 4.0 × 10 -9 mol/cc) are reported. These are viscous non-Newtonian, shear-thinning solutions that also display interfacial tension relaxation, which has both a concentration-dependent and temporal behavior; surface wetting increases as well, as measured by the reduction of contact angle. The measured pool boiling heat transfer from an electrically heated horizontal cylinder in C = 1.0 × 10 -9 mol/cc aqueous solution is found to be enhanced by ~20% over the entire heat flux range (4.0 < q w″ < 200 kW/m 2). In higher concentration solutions, however, heat transfer degrades at low heat fluxes (incipience and partial boiling) with subsequent enhancement (~45% maximum) at high heat fluxes or in the fully-developed nucleate boiling regime. This anomalous boiling behavior in the two regimes, characterized by respectively different ebullience signatures, is shown to be scaled with changes in the liquid-solid interface wetting, vapor-liquid interfacial tension, and shear-thinning viscosity of the polymeric solutions. © 2011 American Institute of Chemical Engineers (AIChE).