Heat Transfer in Pool Boiling with Surfactants

Abstract

Boiling with surfactant is important in many key industrial applications suchas the petrochemical processing, refining, refrigeration, hygiene and personal care,pharmaceutical, and food processing, among others.The aims of this study are experimental determination of the heattransfer coefficient with and without the addition of surfactants to purewater and quantify the effects of surfactant concentration, ionic nature, itsethoxylation, and molecular weight on the nucleate boiling performance ofwater on vertical cylindrical heater.Several different surfactants were employed: [SDS(Sodium Dodecyl Sulfate),SLES (Sodium Lauryl Ether Sulfate) (anionic) ]and [Triton X-100 (OctylphenolEthoxylate) (nonionic)], they have different molecular weights, ionic nature andnumber of ethylene oxide EO groups attached to its polar head.The boiling results show that with the addition of small amounts of surfactants,the saturated nucleate pool boiling heat transfer coefficient of water is found to bealtered due to reduction in the surface tension and this enhances the heattransfer.The enhancement in nucleate pool boiling depends upon wall heat flux (ortemperature difference), concentration of surfactant, ionic nature, molecular weightand number of (EO) group.The heat transfer coefficient is found to increase by asmuch as (81.9%) over that for pure water for SDS solutions while (53 %) for SLESand (45 %) for Triton X-100 at CMC (critical micelle concentration).The enhancement increases with concentration and the enhanced solutions arefound to be with C ≤ CMC. The optimum enhancement is at or near the CMC ofsurfactants. However, the maximum heat transfer enhancement is in the order ofSDS > SLES > Triton X-100, this is also, in the reverse order of their molecularweights and number of (EO) groups.

Keywords

• nucleate pool boiling
• surfactant effect