Experiments and simulations of gas flow through a NiCd battery

Sammanfattning: This report describes the thesis work carried out regarding experiments and simulations of the gas flow through a NiCd battery. The objective of the work was to investigate how different geometries of the flip top vent on the battery and the level of porosity of the flame arresting disc impacted the amount of potassium carbonate created at the outlet of the vent. Experimentsand simulations in COMSOL were performed, where the gained gas flows from the experiments were inserted into the COMSOL models. The physics selected for the models were Free and Porous Media Flow and Particle Tracing. The conclusion drawn from the experiment was that the vent that took the longest time before leakage or bubbling was vent G4, after that vent G2, and then vent G0. Vent G2 was the vent type that had the most potassium carbonate created after the experiment, while the other two vent types had approximately the same amount of potassium carbonate created. The results from the simulations with the experiment could indicate that a lower exit velocity, with a higher gauge pressure in the disc and a shorter time for the particles to travel through the vent, leads to a longer time before fizzing or bubble formation and a lower amount of salt created. The geometry inside the vent leads to different velocities of the gas right before the porous disc. The velocities right before the discs were estimated to be more than double in vent G4 than in G0 and G2. The particles, therefore, travel at a higher velocity towards the porous disc. The higher velocity could potentially be why more particles exit vent G4 than the other vents. However, these correlations cannot be fully established since a limited number of vents were used in the experiment and the simulations.