This document reports the different activities conducted during one semester at the Department of Thermal Engineering of Tsinghua Unversity. This thesis is structured in two different parts because an experimental and numerical study has been performed. Firstly, an experimental study on an initially uniformly distributed nano-particle two-phase flow after passing through a contraction jet has been carried. The study includes a brief review on the state-of-the-art of the nano-particle flow research and the need of further experimental results to develop new results. Using a scanning mobility particle sizer, the study analyses the experimental procedures to ensure the validity of the results obtained. During the experimental work, several conclusions have been reached. This conclusions allow to simplifiy the data acquisition procedures. On top of that, the influence of concentration on the coagulation of nano-particles has also been confirmed. Secondly, a numerical simulation study has been carried to evaluate the properties of an impinging mixer. The main goal was to compare the mixing process between two inlet opposed anular gaseous flows (methane and air) and a mixer with an single anular inlet flow. On top of that, different geometries have been analysed and a the influence of each parameter has been identified.