Abstract: The experimental investigations cover heat transfer of refrigerants R-123 and R-ll flowing through vertical miniehannels of 40 nun wide rectangular section and depths of 1, 1.5 and 2 mni. The heating foil, supplied with controlled direct current, constitutes one of the surfaces of the asymmetrically heated minichannel. The liquid crystal thermography technique is applied in order to measure the two-dimensional temperature field of the heating surface. The investigations focus on the transition from single phase forced convection to nucleate boiling, i.e. in the zone of boiling incipience. The work aims to examine and analyze how the selected parameters (inlet pressure, inlet liquid subcoofing, liquid flow velocity) affect nucleate boiling incipience for various geometry (changeable depth) of the minichannel. Furthermore, the investigations are intended to develop a correlation for the calculations of the Nusselt number under the conditions of boiling incipience in the minichanni:! as a function of changeable parameters in the investigations.
YADDA/CEON