In this thesis analytical, numerical and experimental studies of high heat flux cooling is conducted. The aim of the project is twofold: 1) To design a high heat flux cooling application in cooperation with Danfoss, and 2) to experimentally investigate mini scale heat transfer in mini channels by using planar laser induced fluorescence (PLIF).

In part I especially CFD simulations are used to evaluate the cooling performance of different designs to cool an IGBT power module. The aim is to have low junction temperature and uniform temperature distribution with low pumping power requirements.Two designs are selected to be manufactured: A multijet design and a hybrid design with both jet impingement and mini channels.

The designs are evaluated against the commercial cooling application "Shower Power", where the convective heat transfer coefficient is shown to be higher than for Shower Power at a higher range of pumping powers.

In part II it is shown that it is possible to resolve the temperature gradient along a mini channel sufficiently accurate by using PLIF. It is also shown that the applicability of PLIF over the whole geometry is not found satisfactory, as optical disturbances are found.