Effect of surfactant on flow boiling heat transfer of ethylene glycol/water mixtures in a mini-tube

Abstract

In this study, the effect of adding a surfactant (sodium dodeobcylbenzene sulfonate, SDBS) to ethylene glycol/water mixtures boiling in a vertical mini-tube was studied. Experiments were done using solutions containing 300 ppm by weight of surfactant and the results were compared with those for pure mixture. Local heat transfer coefficient was measured and found to be dependent on the mass quality. Addition of surfactant significantly enhanced the evaporation of saturated liquid, so that the difference between outlet fluid temperature and outlet bubble point temperature of SDBS solutions was much higher than that of ethylene glycol/water mixture. Though the surfactant intensifies the vaporization process, it does not necessarily enhance the heat transfer coefficient. The heat transfer coefficients at two different mass fluxes were compared, and the result could be explained based on the local flow pattern and heat transfer mechanism. After a critical quality, higher quality will deteriorate the heat transfer due to intermittent dryout, therefore adding surfactant to generate more vapor may have a negative effect on the heat transfer of flow boiling in a mini-tube, which is contrast to the experience of enhancing nucleate pool boiling heat transfer with trace surfactant.