Application of Aqueous Solutions of Surfactants in Pulsating Heat Pipe

This article presents an experimental study of colloidal solutions with a focus on the surface properties of colloidal solutions in view of their further application in pulsating heat pipes. Using a tensiometer and the Welhelmi plate method, we carried out a series of measurements of surface tension for various concentrations and temperatures of colloidal solutions with three promising surfactants: CTAB, SLS, and Tween-80. These surfactants in dry form were mixed with water to make a 1% solution and then diluted to weaker concentrations of up to $$3\cdot 10^{-8}$$ mol/l. Dependences of the surface tension on the surfactant concentration were determined, which turned out to be in good agreement with data available in literature. The surface tension values were measured over the temperature range of 20 to 70°C. For several concentrations of the surfactant SLS, the first derivative of the surface tension with respect to the temperature was found to be positive (∂σ/∂T > 0), which means that the interface can be self-wetted. This property may be important in preventing formation of dry spots, which will improve heat transfer in heat pipes.