In the paper the three-dimensional flow fields are numerically simulated in the vertical-shaft mechanical mix tank of a water treatment plant by means of FLUENT software based on the method of Computational Fluid Dyna...In the paper the three-dimensional flow fields are numerically simulated in the vertical-shaft mechanical mix tank of a water treatment plant by means of FLUENT software based on the method of Computational Fluid Dynamics (CFD). The influences of design parameters on flow fields and the mixing effect are analyzed. Firstly,the prediction capability of the turbulence model adopted in simulations is evaluated. And then,the mesh independence is checked up. Finally,the flow fields in various dimensionless blade diameters and dimensionless shaft spans are numerically simulated respectively. The results have shown that the numerical simulation method based on CFD is a feasible assistance for the optimal designs of mixers. Moreover,the optimal design of the blade diameter should take into account both the flow field and the power consumption. The optimization of the shaft span is to achieve a relatively even distribution of the flow field without any rupture. With the consideration of an optimal design,the dimensionless blade diameter and dimensionless shaft span should be 0.45 and 0.57 respectively in the case.展开更多
Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in...Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems.The same nutrient transport system can be mimicked in the flow channel design of a PEMFC,to aid even reactant distribution and better water management.In this work,the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates,on the performance of a PEMFC was examined experimentally at various operating conditions.A PEMFC of 49 cm2 area,with a Nafion 212 membrane with a 40%catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm-2 on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate,and was tested on a programmable fuel-cell test station.The impact of the working parameters like reactants’relative humidity(RH),back pressure and fuel cell temperature on the performance of the fuel cell was examined;the operating pressure remains constant at 0.1 MPa.It was observed that the best performance was attained at a back pressure of 0.3 MPa,75°C operating temperature and 100%RH.The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa,and the other parameters such as operating temperature,RH and back pressure were set as 75°C,100%and 0.3 MPa.The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field.It was observed that among the different flow channel designs considered,the leaf channel design gives the best output in terms of power density.Further,the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design.The PEMFC with the interdigitated leaf channel design was found to generate 6.72%more power density than the non-interdigitated leaf channel design.The fuel cell with interdigitated leaf channel design generated5.58%more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.展开更多
基金Sponsored by the Science and Technology Projects of Heilongjiang Province (Grant No.GB07C20202 and LC06C16)
文摘In the paper the three-dimensional flow fields are numerically simulated in the vertical-shaft mechanical mix tank of a water treatment plant by means of FLUENT software based on the method of Computational Fluid Dynamics (CFD). The influences of design parameters on flow fields and the mixing effect are analyzed. Firstly,the prediction capability of the turbulence model adopted in simulations is evaluated. And then,the mesh independence is checked up. Finally,the flow fields in various dimensionless blade diameters and dimensionless shaft spans are numerically simulated respectively. The results have shown that the numerical simulation method based on CFD is a feasible assistance for the optimal designs of mixers. Moreover,the optimal design of the blade diameter should take into account both the flow field and the power consumption. The optimization of the shaft span is to achieve a relatively even distribution of the flow field without any rupture. With the consideration of an optimal design,the dimensionless blade diameter and dimensionless shaft span should be 0.45 and 0.57 respectively in the case.
文摘Performance of the proton exchange membrane fuel cell(PEMFC)is appreciably affected by the channel geometry.The branching structure of a plant leaf and human lung is an efficient network to distribute the nutrients in the respective systems.The same nutrient transport system can be mimicked in the flow channel design of a PEMFC,to aid even reactant distribution and better water management.In this work,the effect of bio-inspired flow field designs such as lung and leaf channel design bipolar plates,on the performance of a PEMFC was examined experimentally at various operating conditions.A PEMFC of 49 cm2 area,with a Nafion 212 membrane with a 40%catalyst loading of 0.4 mg·cm-2 on the anode side and also 0.6 mg·cm-2 on the cathode side is assembled by incorporating the bio-inspired channel bipolar plate,and was tested on a programmable fuel-cell test station.The impact of the working parameters like reactants’relative humidity(RH),back pressure and fuel cell temperature on the performance of the fuel cell was examined;the operating pressure remains constant at 0.1 MPa.It was observed that the best performance was attained at a back pressure of 0.3 MPa,75°C operating temperature and 100%RH.The three flow channels were also compared at different operating pressures ranging from 0.1 MPa to 0.3 MPa,and the other parameters such as operating temperature,RH and back pressure were set as 75°C,100%and 0.3 MPa.The experimental outcomes of the PEMFC with bio-inspired channels were compared with the experimental results of a conventional triple serpentine flow field.It was observed that among the different flow channel designs considered,the leaf channel design gives the best output in terms of power density.Further,the experimental results of the leaf channel design were compared with those of the interdigitated leaf channel design.The PEMFC with the interdigitated leaf channel design was found to generate 6.72%more power density than the non-interdigitated leaf channel design.The fuel cell with interdigitated leaf channel design generated5.58%more net power density than the fuel cell with non-interdigitated leaf channel design after considering the parasitic losses.
