The working principle of air-lift pumps can be applied to Direct carbon fuel cell (DCFC) systems, which can handle high-temperature molten coal-laden carbonate fuels. In this study, the pumping performance and essential hydrodynamic features of an air-lift pump with high submergence ratio are studied experimentally. Liquid anode media composed of a mixture of carbonaceous fuels and molten carbonates that surround solid-oxide electrolyte tubular cells in DCFC systems are considered. In this system, a certain amount of CO2 is injected into the liquid fuel media not only to prevent carbonate decomposition, but also to recirculate or transport fuel media. CO2 injection is essential to stabilize the system and enhance reaction. Water and air are selected as simulants of molten fuel and CO2, respectively. Then, a blunt body is inserted into the single hollow tube (Model system), which is then shaped as a tubular cell. Air, which is supplied from the bottom of the tube, flows up in the shape of a bubble and entrains water inside the tube. Then, water is discharged. The flow rate of the water discharged from the top of the tube is measured using the following parameters: Tube diameter, blunt-body diameter, and submergence ratio. Bubble pattern formations in the tube are also observed by varying parameter combinations. Four to five distinct bubble patterns can be observed depending on air flow rate comparisons. The discharge flow rates from the blunt-body-insertion tube are correlated with those from the hollow tube. Finally, two tube parameters, namely, the same cross-sectional flow areas and the same hydraulic diameters, are considered. Good correlations were established for the flow area parameter.
