Apart from a relation with surface tension gradients, the knowledge of Marangoni convection remains incomplete, especially in the operative range of high-temperature absorption cycles. Preliminary surface tension measurements have shown weaker surface tension gradients at higher temperatures. Consistently, this research demonstrates that the intensity of Marangoni convection weakens in the temperature range of absorption heat transformers and heat amplifiers, and suggests that, owing to the higher surfactant solubility at higher solution temperature, a temperature-limitation of the phenomenon may be identified.

A dedicated experimental equipment was constructed to test this research hypothesis. Tests are conducted to induce, quantify, and visualize Marangoni convection in a temperature- and pressure-controlled environment. Fluorescent uranine and measurements of the absorption rate are used, respectively, to clarify the intensity of the phenomenon qualitatively and quantitatively in a range of solution temperatures between 30°C and 80°C. Initial temperature and mass fraction of the Lithium-Bromide solution are generated with a thermal bath and a pressure-controlled vapor environment, respectively. Subsequently, absorption is initiated by releasing vapour at higher pressure than equilibrium. Finally, the intensity of Marangoni convection is measured by comparing average absorption mass flux from tests without surfactants to results obtained at corresponding conditions with 80 ppm of 1-Octanol.