AN INTEGRATED GAS-LIQUID FLOW ANALYSER AND ITS APPLICATIONS TO PERFORMANCE PREDICTIONS IN WATER ELECTROLYSIS SYSTEMS

A high-pressure water electrolysis system has been investigated numerically and experimentally. The overall numerical model is based on non-standard physical sub-models added to the PHOENICS Computational Fluid Dynamics (CFD) code and the Inter-Phase Slip Algorithm (IPSA). In the water electrolysis system, a hydrogen gas-electrolyte mixture forms a two-phase flow, driven by natural circulation. The advanced two-phase flow CFD model, which calculates the 3D distributions of pressure, gas and liquid velocities and gas and liquid volume fractions, accounts for all the major components in the system, and appropriate constitutive equations for two-phase flow parameters were selected for various parts of the system, such as cell stack, riser, separator and downcomer. The model was validated using comparisons of predicted liquid flow rate with the liquid flow rate measured in the downcomer, where a single-phase liquid flow existed. The effects of pressure, current density, number of cells, and bubble size were investigated with the numerical model. The numerical predictions matched the general trends obtained from the experimental results with regard to the effects of pressure and current density on the liquid flow rate. The differences between the measured and predicted liquid flow rates are acceptable. The validated CFD model is being used as a cell design tool at Hydrogenics Corporation