An improved version of the Twister Supersonic Gas separator concept was tested in Gasunie Research Laboratories in the Netherlands during 2005 and 2006 in a closed loop test facility using a multiphase pump. Advanced CFD models were used to improve the internal design of the Twister separator, leading to a new design with a reduced overall pressure drop. The most important aim of the experimental work was to verify CFD model calculations of pressure drop and component recovery performance. In this paper the CFD model used for the prediction of the results is described. The results of one experiment are compared with the results from CFD.