A dense particles suspension was tested in a high temperature single tube on-sun solar receiver at the French National Centre for Scientific Research (in French: Centre National de la Recherche Scientifique = CNRS) solar facility. A powder outlet temperature as high as 750 degrees C was measured thus proving the capacity of this heat transfer fluid concept to reach high operating temperatures. The wall-to-suspension heat transfer coefficient was calculated on the basis of detailed temperature measurements and accounting for the strong recirculation phenomena occurring at the tube wall. It ranges from 420 W/m(2) K to 1100 W/m(2) K for a solid mass flux of 10 kg/m(2) s and 45 kg/m(2) s, respectively. The temperature increase positively influences the heat transfer coefficient; with a 30% increase measured between similar to 200 degrees C and 600 degrees C average powder temperatures. Finally, a correlation is proposed to predict the dependency of the heat transfer coefficient and solid mass flux. (C) 2015 Elsevier Ltd. All rights reserved.