A biosurfactant as prospective additive for pool boiling heat transfer enhancement

Abstract

Compared to chemical or synthetic surfactants, biosurfactants have been less explored in heat transfer applications. In the present work heat transfer performance of a biosurfactant (Rhamnolipid) solution in pool boiling experiments has been reported. Pool boiling experiments have been performed on a smooth copper surface with aqueous Rhamnolipid solutions at different concentrations and results have been compared with that of DI water. Surface tension and viscosity of newly developed surfactant solutions have been experimentally measured. Critical micelles concentration (CMC) of aqueous Rhamnolipid solution has been observed at 200 ppm. Significant enhancement of heat transfer coefficient is observed with Rhamnolipid solution at CMC value. It reports 200% enhancement in heat transfer coefficient compared to that with pure water. Active nucleation sites and less coalescence of growing of bubbles contribute for heat transfer enhancement in surfactant solutions. Like other surfactants critical heat flux (CHF) value of Rhamnolipid solution at CMC is observed less than that of pure water. However, reduction in CHF (23%) of present surfactant solution is less than the reduction in CHF (≈50%) of other surfactants. Present Rhamnolipids solution shows better heat transfer performance and higher CHF value compared to SDS surfactant. Moreover, it shows better heat transfer performance in comparison to other biodegradable surfactants reported in the literature.