measuring method. The characteristic length of the channels investigated was varied in a region of 300 µm up to 700 µm. The channels were designed as Joule heating pipes. So, the evaporation was reached under conditions of nearly constant heat fluxes at the heating wall of the channel.
A thermographic measuring method was used to examine the wall temperature. The high spatial and temporal resolution of this thermographic measuring method makes it possible to detect the axial position of the different boiling regions. Furthermore, it allows conclusions on which flow conditions occur in the different sections of the channel.
Experimental results are shown with water and n-heptane as the fluid to be vaporized. The results of measurements are discussed and a correlation of the location where the dryout starts with the characteristic parameters is given. The dependency of the pressure drop in such channels on the technological parameters has also been presented.