Effects of channel diameter on flow pattern and pressure drop for air-water flow in serpentine gas channels of PEM fuel cell-An Ex situ experiment

Ex-situ experimental investigation of air-water two phase flow characteristics are carried out in rectangular serpentine mini and micro-channels. The test sections to be studied are made up of acrylic and are of three different hydraulic diameters of 1.65 mm, 1.00 mm and 0.65 mm with the corresponding length of 50 mm. Experiments are performed for different combinations of superficial velocities of air and water ranging between 0.0011 m/s and 0.33 m/s and 0.33 m/s to 16.66 m/s, respectively. The effect of channel orientation on various parameters is also studied. The visualisation of two phase is accomplished by high-speed camera. The flow pattern maps developed by closely scrutinizing each flow rate combinations are presented. Mal-distribution occurred in horizontal orientation of micro channel. However, vertical orientation of micro channel favoured draining of water, thereby encountered lesser pressure drop than mini channel. New correlation based on various dimensionless numbers has been proposed for modelling the pressure drop.