## 2 Literature Survey  
### PEMFC and Various Design  
Neutron imaging techniques have been used by [7] for determining the distribution of water in the membrane electrolytes of the PEMFC and have been used as benchmark data for validating numerically predicted results by using a CFD code. The local distribution of liquid water as predicted by the model are compared to those obtained by using the techniques of neutron imaging at various different operating parameters. The numerical CFD experiment has been validated with experimental data by using polarization curves. The 3D CFD simulations for the flow fields in the bipolar plate for hydrogen flow in a PEMFC was performed by [8]. The author has considered different flow field models for the bipolar plates by varying the geometry. OPEN FOAM software has been used to analyze the flow simulations and to obtain the velocity and pressure distributions. The variable parameters considered for these straight parallel flow fields are the depth, shape, and width of the channels. It is reported that the geometric changes in the structure of the parallel flow field could affect the flow and pressure distribution. The numerical simulation on a wavy flow field structure and a vertical flow field structure using CFD code on PEM fuel cell performance is carried out by [9]. They reported that due to the wavy flow fields, vertical fluid flows were established, which helps in improving the effective diffusion of oxygen and delay concentration losses for high current density. The wavy structure helps to reduce concentration losses even at lower stoichiometry. Moreover, the wavy flow field design also helps to maintain a uniform current density and gas flow. A numerical investigation on the two-phase flow occurring in a PEMFC with tapered channel flow using air and water [10]. They reported more effective water removal for tapered channels due to increased air velocity. The channel tapering effect on fuel cell performance was significant at higher temperatures, low voltages, and high current density. When compared with normal rectangular channels, the water is removed more effectively with the tapered flow channel. A 3D CFD model of a new type of flow field for a PEMFC which has a structure like the branches of a tree [11]. They studied three different tree types of flow field configuration. They were compared to the conventional flow field types like the parallel and the serpentine. They reported that the tree-shaped designs ensure a much more uniform distribution of the reactants and lower pressure drop when compared to the conventional patterns. In the tree-shaped design, it was found that as the bifurcations increase, and there is an increase in the active area, which increases the cell performance. The numerical investigation on nature-inspired flow field design for a PEMFC was conducted by [12]. They also stated the role of CFD models in analyzing these nature-inspired flow field designs. Various nature-inspired designs have been considered, such as fractal designs, heuristic, biologically inspired designs, and formal, biologically inspired designs. A comparison of these designs to the conventional flow fields has also been presented, and the various challenges regarding the development of these nature-inspired flow designs. A 3D CFD investigation of the liquid water dynamics on the performance of PEMFC was conducted by [1]. The volume of the fluid model has been used for the simulation purpose. It was shown that droplets from inner and outer pores tend to move along the lower edge of the gas channel. They reported that there is an increase in GDL water surface coverage and a decrease in water volume fraction. The proper balance between the water volume fraction and the GDL surface water coverage ratio will optimize the performance of the fuel cell. A numerical simulation on a new compound flow-field design using a 3D CFD model was performed. They compared the performance characteristics between conventional parallel and serpentine flow fields [13].