Experimental Investigation of Sub-Cooled Flow Boiling Heat Transfer in Single Rectangular Metallic Micro-Channel

Abstract

In this study, an experimental investigation on the flow boiling heat transfer in single rectangular micro-channel was carried out. The micro-channel was formed by machining 300 μm wide x 700 μm deep groove (i.e. a hydraulic diameter 420 μm) into the surface of brass block having length of 60 mm. The working fluid was deionized water. The experiments were carried out with the mass flux range (300-600 kg/m².sec), and flux of heat (based on wall) 5.4 to 376.5 kW/m², inlet sub-cooling of 20 K and 1 atm. working pressure. The results of this study have shown that at heat fluxes with lower range, the local coefficient of heat transfer increased with increasing the flux of heat. This trend is reversed when heat fluxes exceed 64.2, 77.9, 93.8 and 116.7 kW/m² for mass fluxes 300, 400, 500 and 600 kg/m².s respectively, where the heat transfer coefficient decreases as the heat flux increases and reach a constant value at the highest heat flux. The experimental results are compared to heat transfer correlations of minichannel and microscale, these correlations gave the results reasonably well.