Water plays an important role in the operation of Fuel Cell. It determines where the electrochemical reactions should or should not occur. The purpose of this study is to investigate the transport characteristics of vapor through all components of an electrode and how they are related to the cell performance. In the transmit experiment of cell produce water which prove the level of water steam transmission characteristics has relative relations with the measurements of water transport in fuel cell. In a sum, the electrode with higher water steam transmission characteristics, the measurement of water transport will also be higher. From cell performance measure experiment, we can found that water steam transmission characteristics have the opposite relation with the concentration loss¡]mass transfer behavior¡^. As cell working on high current density, water will not clog easily under the great quality transmit electrode. Further, catalyst layer that has enough concentration would not cause the cell performance dismiss with the follow up reactions and it represents that cell performs batter with mass transfer. According to the experiment, PTFE in MPL with smaller amount has better performance to fuel cell. What the differences between the presentation of water as liquid state or gaseous state when it transmits in electrode? We can discover the rate of gaseous state water is faster compared to liquid state water when transmitting through MEA in a simple experiment. We assume that gaseous state of water is the first type within the electrode.

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In the coalescence zone, we obtained ozone concentration profiles of pairs of bubbles in vertical and oblique alignments, which show rapid decrease in the interaction period and more gradual decline in the late stages of coalescence. / In the grid region, the hydrodynamics of a stream of gas injected vertically into a bed of solids was observed in a semi-circular column containing particles of several sizes and densities. This was found to be similar to those reported in the literature. Furthermore, experiments were carried out in a 15 cm diameter column to characterize the magnitude of gas transfer from spout to dense phase and from forming bubbles to dense phase. The results show that the transfer from the spout is mainly due to convective gas outflow with some molecular diffusion. While during bubble formation, the transfer seems to be molecular diffusion only, being similar in magnitude to single bubbles in fluidized beds.

In the pulp and paper industry, the interaction between the gas, liquid, and solid phases occurring in various unit operations is often not clearly understood. Such multi-phase operations include flotation deinking (a separation process of paper fibres in the recycling process) as well as the delignification and bleaching operations in the kraft pulping process. Much of the design, operation, and optimization of such processing equipment are dependent upon past experience as well as trial-and-error methodologies. Pulp fibre suspensions possess a complex and unique rheology. The unpredictability of the behaviour of pulp suspensions at any given mass concentration is due to the bonding between the fibres resulting in network formation (which depends on suspension consistency) with this interaction creating complexity in fluid flow in various unit operations. This thesis describes the gas hydrodynamic behaviour and gas-liquid mass transfer characteristic in low- and medium-consistency pulp suspensions in batch operation. First, the hydrodynamic behaviour of the gas phase (air) in water and pulp suspensions having mass concentrations up to Cm = 7% is examined by visually observing and recording the bubble shape, size, and rise velocity in a rectangular channel. Results are obtained using a high-speed video camera. Second, the hydrodynamic behaviour is described in terms of the gas holdup along with axial and radial gas phase distributions in water and kraft pulp suspensions having mass concentrations between Cm = 0.5 and 9% in a batch-operated cylindrical bubble column. The gas holdup results are compared using three methods: the suspension height method, the pressure difference method, and the electrical resistance tomography (ERT) method. Finally, the volumetric gas-liquid mass transfer characteristic of air in water and kraft pulp suspensions having mass concentrations up to Cm = 4% is examined in the same bubble column in batch-operation using a dissolved oxygen probe. Experimental results were comparable to that in literature for water and for pulp fibre suspensions having Cm < 2%. The presence of fibres had a significant effect on the gas holdup and mass transfer characteristic with results providing insight on the limitations that exist in industrial pulp unit operations.

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