Heat pipes with binary mixtures and inverse Marangoni effects for microgravity applications

Numerical and experimental investigations have been carried out to understand the role of Marangoni effects in heat pipes with aqueous solutions of long-chain alcohols, proposed to replace common pure liquids used in conventional heat pipes. Laboratory measurements of surface tensions have been carried out for a number of binary solutions at different temperatures and concentrations, to identify the most promising two-component mixtures with a nonlinear dependence of the surface tension with temperature. Fundamental studies on Marangoni flows in binary mixtures, for different experimental configurations of interest, show the potential advantages of these new working fluids.A number of tests have been performed with grooved heat pipes, filled with aqueous solutions with the appropriate alcohol concentrations. The results show improved performances of these heat pipes, when compared to conventional commercial water heat pipes.