Two-phase flow in converging and diverging microchannels with CO2 bubbles produced by chemical reactions |
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| Affiliation: | 1. Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China;2. Applied and Plasma Physics, School of Physics (A28), University of Sydney, Sydney, NSW 2006, Australia;3. Electrical Discharge and Plasma Lab, Tel Aviv University, POB 39040, Tel Aviv 69978, Israel;1. School of Sciences, Nanjing University of Science and Technology, Nanjing 210094, China;2. Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong Special Administrative Region;3. College of Information Technology, Shanghai Ocean University, Shanghai 201306, China;4. City University of Hong Kong Shenzhen Research Institute Building, Shenzhen Hi-Tech Industrial Park, Nanshan District, Shenzhen, China;1. Institute of Refrigeration and Cryogenics, Zhejiang University, Hangzhou, China;2. Division of Building Science and Technology, City University of Hong Kong, Kowloon, Hong Kong;1. Doshisha University, Department of Chemical Engineering and Material Science, 1-3 Miyakodani, Tatara, Kyotanabe, Kyoto 610-0321 Japan;2. Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094 Japan;3. Kobe Gakuin University, Faculty of Pharmaceutical Sciences, 1-1-3 Minatojima, Chuo-ku, Kobe 650-8586, Japan |
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| Abstract: | The present study investigates experimentally the evolution of two-phase flow pattern and pressure drop in the converging and diverging, silicon-based microchannels with mean hydraulic diameter of 128 μm and CO2 bubbles produced by chemical reactions of sulfuric acid (H2SO4) and sodium bicarbonate (NaHCO3). Three different concentrations of 0.2, 0.5 and 0.8 mol/L of each reactant at the inlet before mixing and 10 different flow rates from 1.60 × 10−9 m3/s to 16.0 × 10−9 m3/s are studied. Flow visualization is made possible by using a high-speed digital camera. It is found that the present design of the microchannel, with the inlet chamber, results in much more intensive chemical reactions in the diverging microchannel than that in the converging one. The void fractions at the entrance and exit regions and pressure drop through the channel are also measured. The results reveals that the presence of small void fraction, <0.1, at the inlet may promote CO2 generation in the microchannel, irrespective of the channel is converging or diverging, indicating the agitation effects of bubbly flow in the microchannel. The increase of inlet concentration of reactants does not increase the pressure drop in the converging microchannel significantly, while the inlet concentration presents significant but mild effects on the pressure drop in the diverging microchannel. The two-phase frictional multiplier may be positively correlated with the mean void fraction in the channel linearly, and the data agree well with predictions from the correlations in the literature. |
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