Experimental investigation of transient boiling heat transfer in microchannels

This paper presents an experimental investigation of flow boiling heat transfer in a single 0.3 × 12.7 mm2 rectangular microchannel. Water and ethanol are employed as test fluids. The test section, which is made of the nickel alloy Inconel 600, is electrically heated. The examined parameter ranges are: mass fluxes between 50 and 500 kg/m2s and heat fluxes up to 400 kW/m2 at an outlet pressure of 0.1 MPa. Infrared thermography is employed to register the outer wall temperatures of the channel. This measurement method is especially appropriate for the analysis of the transient behavior of boiling in microchannels, which has been often reported in the literature. Infrared images of the test section are recorded at a frequency of 150 Hz using the half image mode. Data are collected over 25 s and the behavior of the obtained wall temperatures is analyzed. Local heat transfer coefficients are then calculated from the time averaged outer wall temperatures. Finally, the experimental values are compared with widely used correlations.