关键词: 微流体学, 燃料电池, 格子动理格式, 格子Boltzmann, 传质, 流动

Abstract:

Cotton threads are employed as flow channels in thread-based microfluidic fuel cells, which eliminates external pumps and benefits for miniaturization, showing a promising power source for portable microfluidic devices. However, the cell performance is limited by the fuel transfer at the anode. To better understand the fuel transfer characteristics coupled with electrochemical reaction at the anode, lattice Boltzmann (LB) method was used for the cotton thread-based microfluidic fuel cell. A three-dimensional numerical model of the cotton thread flow channel was developed and the distributions of velocity and concentration of fuel were calculated. The effects of inlet fuel concentration and flow rate on performance and mass transfer characteristics of anode were also discussed. The results show that LB results agree well with experimental results of the anode polarization curve. The velocity of fuel inside the cotton thread is lower than that in the gaps among threads. The fuel concentration decreases along the flow direction under different anodic over potentials and larger decrement is found at higher anodic over potentials. An increasing average current density is obtained with an increase in the inlet fuel concentration, leading to a better anode performance. Moreover, with an increase in the inlet fuel flow rate, a greater difference in the fuel concentration is observed between the location where the cotton thread contacts with reaction interface and other regions. When the inlet flow is low, the difference in concentration is small and the concentration in the rear part of the flow channel is low.

Key words: microfluidics, fuel cells, lattice kinetic scheme, lattice Boltzmann, mass transfer, flow