Experimental thermal hydraulics is needed to increase knowledge on functioning of nuclear power plants (NPP) and thus to enhance the safety of NPPs. Test facilities at LUT nuclear safety research laboratory are used either to ensure the functioning of safety systems of NPPs or to gain data for the validation of the computer codes. These codes are used to analyze the safety features of light water reactors. In the doctoral research advanced measurement techniques are used to acquire more information on thermal hydraulics of NPPs. Among these are particle image velocimetry (PIV) and wire mesh sensors (WMS).
Particle image velocimetry is a flow visualization technique, which allows for capturing velocity information of flow fields. PIV is based on illuminating of small tracer particles added to the flow with a laser apparatus. The movement of these illuminated particles is recorded with a camera system and converted into velocity information with a data acquisition system.
Wire mesh sensors are used to gain information on multiphase flows. WMS is based on the difference of multiphase flow phases regarding an electrical property, i.e. conductivity or permittivity/capacitance. WMS can be used to determine void fraction distributions, bubble size distributions and velocity distributions of multiphase flows.