Effect of Operating Pressure on Flow Boiling Heat Transfer in Microchannels

This paper reports an experimental study of flow boiling in a microchannel and this work has been focused on the investigation on the effect of operating pressure. The experimental apparatus consisted mainly of peristaltic pump, preheater, microchannel test tube, and vacuum chamber for control of operating pressure. Deionized water was used as the working fluid. The test section was a round tube of 310 μm inside diameter, made of 304 stainless steel. The experiment has been performed for the conditions of heat flux of 35∼85 kW/m², mass flux of 200∼300 kg/m²s (160∼250 of liquid Reynolds numbers), and the operating pressure of 10∼20 kPa. The measured flow boiling heat transfer coefficients in the microchannel were in the range of 3.0 to 27 kW/m²K and the experimental data showed that the flow boiling heat transfer coefficients in microchannels were affected mainly by the wall heat flux and the operating pressure.