Effects of surface tension and binary diffusion on pool boiling of dilute solutions: An experimental assessment

Pool boiling heat transfer with dilute binary mixtures introduces two addit ional effects due to binary diffusion, and due to change in the surface ten sion. The secondary effects due to changes in contact angle and wetting cha racteristics may also play a role. The present study focuses on identifying these effects for dilute aqueous solutions of ethylene glycol. Pool boilin g experiments are conducted to generate data in the range of one to ten per cent mass fraction. It is found that in the low concentration region, the b inary diffusion effects are insignificant for aqueous solutions of ethylene glycol, and a slight improvement in heat transfer coefficient is observed over the pure water value. The binary diffusion effects are related to a vo latility parameter, V-1. The heat transfer coefficient does not degrade in the region where V-1 < 0.03, and the surface tension does nor change apprec iably compared to pure water value. This points to the possibility that the changes in contact angle and wetting characteristics play an important rol e in the pool boiling heal transfer.