Abstract
The proposed study aims to develop a low pressure drop, highly stable and efficient microchannel evaporator with binary component mixtures, such as methanol-water mixtures. This study conducts experiments, flow visualization and modeling of convective boiling of methanol-water mixtures, with different concentrations and flow rates, in a diverging microchannel. Flow boiling curve, two-phase flow pattern and two-phase flow pressure drop are explored. All of the microchannels etched on SOI wafer using MEMS technology, such as bulk micro-machining and anodic bonding. The experimental results reveal that boiling, heat flux increases with increasing superheat, but the slope decreases correspondingly. On the other hand, the results clearly indicate the strong influence of liquid mole fraction on the onset of boiling and the mixture composition results in a pivotal augmentation or reduction in heat transfer. Both critical heat flux and boiling heat transfer are enhanced at xm=0.3 due to the strong Marangoni effect. Flow visualization demonstrates five flow regimes : bubbly flow, slug flow, annular flow, film breakup, and dry out. Nevertheless, the film breakup regime plays an important role in triggering the CHF. At xm=0.3, the span of heat flux and superheat range helps to heighten the given input heat flux without dryout, and the highest CHF is demonstrated one other concentration. The results of present study suggest that by adding suitable amount of methanol in water may result in higher boiling heat transfer capability and higher two-phase flow pressure drop than pure water.