Investigation of counter-current mixing in a continuous hydrothermal flow reactor

► Counter-current mixing for the hydrothermal synthesis of nanoparticles was studied. ► Temperature profiles were measured at conditions near to the critical point of water. ► The superheated water temperature fell inside the mixer owing to heat lost to the cooler products. ► Rates of heat transfer and forces acting on the jet or plume of superheated water are estimated.