SEARCH

SEARCH BY CITATION

Keywords:

  • heat transfer;
  • interfacial processes;
  • bubble phenomena;
  • evaporation;
  • rheology

Abstract

Nucleate boiling characteristics of aqueous solutions of hydroxyl ethyl cellulose (HEC QP-300; M ∼ 600 kg/mol) in different concentrations (1.0 × 10−9C ≤ 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 < qmath image < 200 kW/m2). 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 J, 2012