Litan Kumar Saha

Numerical Study of Pressure Drop in the Separator Channel and Gas Diffusion Layer of Polymer Electrolyte Fuel Cell and Deformation Effect of Porous Media

The flow behavior in the separator channel and gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC) has been investigated by using a transient, isothermal and three-dimensional numerical model. Gas channel and gas diffusion layers are considered as the important parts of PEFC as they transport reactant gases to the catalyst layer and also byproduct from the catalyst layer. The deformation of GDL plays an important role on the performance of polymer electrolyte fuel cell since the physical properties such as porosity and permeability of the GDL and the cross sectional area of the gas channel are affected by the structural deformation of GDL. In this present investigation, non-uniform deformations shape of GDL are taken into consideration and chosen as in the experimental data. Numerical simulations are performed for a wide range of porosity and permeability values. Further, the effects of these parameters on the pressure distribution are measured. It is revealed that the increase of porosity and permeability parameter caused the decrease of pressure drop (difference of pressure from inlet and outlet) but the decreasing rate is not uniform. It is also found that there is an effective range of porosity and permeability values for which these parameters have a very strong effect on the pressure drop. The results obtained by numerical simulation are also compared with the experimental as well as theoretical solution.Copyright

The Cross Flow Mechanism in the Micro Channel of a Polymer Electrolyte Fuel Cell

In this article we presented the recent activities in the field of gas flow in the micro channel and porous media of a polymer electrolyte fuel cell (PEFC). The gas flow behavior in the micro-channel, especially in the case of serpentine channel is very complex due to the appearance of cross flow through the gas diffusion layer (GDL). The gas flow behavior in the separator channel and GDL of a PEFC has been studied by using a transient, isothermal and three dimensional numerical models. To predict gas flow phenomena accurately the precise calculation of mass conversation is necessary which is strictly maintained in our present simulation. The effects of physical characteristics and geometrical properties have been investigated to quantify the amount of cross flow and pressure loss. The cross flow has been investigated in terms of volume mass flux through the GDL under the rib. The ratio cross flow rate to the total flow rate increases when gas channel pitch length decreased. Moreover, with increasing of permeability this ratio also increases. The effect of cross flow and bend region characteristics on the pressure loss has been identified. In addition, to isolate the contribution of cross flow on the performance of fuel cell, the simulation was carried out with electrochemical reaction using parallel straight channel. We designed a parallel flow field to induce artificial cross flow through the GDL. The numerical results show that the flow cross-over through the GDL under the rib significantly facilitate the oxygen transport towards the catalyst layer. Therefore, it is possible to overcome the oxygen transport limitation. Consequently, the cross flow can increase the current density by reducing the oxygen transport limitation, although this also increases the non-uniformity in current density.Copyright

Prediction of Flow Crossover in the GDL of PEFC Using Serpentine Flow Channel

A serpentine flow channel is one of the most common and practical channel layouts for PEFCs since it ensures the removal of water produced in the cell with an acceptable parasitic load. The operating parameters such as temperature, pressure and flow distribution in the flow channel and GDL has a great influence on the performance of PEFCs. It is desired to have an optimum pressure drop because a certain pressure drop helps to remove excess liquid water from the fuel cell, too much of pressure drop would increase parasitic power needed for the pumping air through the fuel cell. In order to accurately estimate the pressure drop precise calculation of mass conservation is necessary. Flow crossover in the serpentine channel and GDL of PEFC has been investigated by using a transient, non-isothermal and three-dimensional numerical model. Considerable amount of cross flow through GDL is found and its influence on the pressure variation in the channel is identified. The results obtained by numerical simulation are also compared with the experimental as well as theoretical solution.Copyright