2.1. Construction of cell

Several flow-channel dimensions of serpentine flow field as listed in Table 1 have been grooved on graphite plates of the dimension 30 cm × 30 cm × 1.5 cm in which the active area of the grooved channels was approximately 20 cm × 21 cm. Channel widths of 3, 4, 5 mm, depths of 3, 4 mm and rib widths of 2, 3 mm have been chosen for the study as listed in Table 1. Schematic of serpentine flow field is shown in Fig. 1. The graphite plates had given 5 cm as the overhead dimension on each side to accommodate compressible gasket (Fig. 1c) to arrest the leakage of electrolyte from active area. The studies of few flow-channel dimensions were extended to cell active area of 900 cm² (30 cm × 30 cm). The optimal flow-channel configuration (5 × 2 × 3) (channel width × rib width × channel depth) has been studied systematically on three cell active areas namely 416 cm² (20.8 cm × 20 cm), 918 cm² (30.6 cm × 30 cm) and 1495 cm² (29.9 cm × 30 cm) for various flow rates and current densities. Graphite felt (GFA 6EA from SGL Carbon) was placed on the active areas of the graphite plates (as both anode and cathode material), the membrane (Nafion 117) was sandwiched between the anode and cathode felt, copper plates of equal dimension as graphite plates were placed next to the them followed by end supporting plates which were insulated from the current carrying copper plates and the cell was tightened to the required level of electrode compression ratio (CR), which is defined in the Eq. (1), using suitable thickness of silicone gasket. An assembled single cell in operation and its components can be seen in Fig. 2.

where t_c is the thickness of felt after compression and t_i is the initial thickness before compression.