Tham khảo tài liệu 'heat transfer theoretical analysis experimental investigations systems part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 430 Heat Transfer - Theoretical Analysis Experimental Investigations and Industrial Systems was made of transparent polycarbonate PC . A high-speed video camera VITcam CTC with a CCTV C-mount lens SE2514 AVENIR was employed to capture two-phase flow images in the anode flow field. A shutter speed of 3996 ps a recording speed of 250 frames s and a resolution of 1280x1024 pixels were set to visualize and record two-phase flow in the anode flow field. Oxygen gas with purity of without humidification was used as oxidant reactant. The oxygen gas flow rate was controlled by a mass flow controller Cole Parmer CZ-32907-67 at constant flow rate of 400 mL min. The prepared methanol solution was stored in a storage bag and was driven by a peristaltic pump and sent to a liquid flow meter Cole Parmer CZ-32908-43 . The oxygen gas and the methanol solution were heated up before flowing into the anode channels. The produced mixtures from DMFC were sent to two separate containers. Fig. 13. Influence of gravity on the power performance of DMFC Wan et al. 2006 . Fig. 13 shows the preliminary results using gold-plating stainless steel as both the anode and the cathode bipolar plates Wan et al. 2006 . In despite of the deterioration of performance of the fuel cell it is very evident that the cell performance falls more strongly with the degree of concentration polarization deepening. After re-design of the anode and the cathode bipolar plates an in-situ visualization of two-phase flow inside anode flow bed of a small liquid fed direct methanol fuel cells in normal and reduced gravity has been conducted in a drop tower Beijing. The experimental results indicated that when the fuel cell orientation is vertical two-phase flow pattern in anode channels can evolve from bubbly flow in normal gravity into slug flow in microgravity Fig. 14 . In normal gravity environment the gravitational buoyancy is the principal detaching force. The carbon dioxide bubbles were produced uniformly with
