Numerical Study of Flow Characteristic and Heat Transfer on Ultracapacitor Stack with Reynolds Number Variations

Ultracapacitor is a reversible electrochemical energy storage device. The use of ultracapacitor can be found in a machine that need to store high density energy, such as automotive, wind energy powerplant and industry. In automotive, it is used as an energy storage in electrical car and for the engine start-up. Ultra capacitor is also used as the electronic conditioner to improve the quality of power extracted on wind turbine. In industry, it can be used as emergency power supply. In the use of ultracapacitor, aging often occurs in consequence of the increasing temperature that causes the destruction in ultracapacitor. Because of that, a cooling system that is capable to maintain the working temperature, is used. The common one is to use the forced air cooling. In this study, the effect of different volumetric flow rate of the fan and the allowable electric current that the ultracapacitor can withstand are investigated. The ultracapacitors were modeled in three dimensions and simulated by using the Reynolds Averaged Navier-Stokes method. The simulation is performed in a steady, segregated manner, with the assumptions of incompressible flow, with various turbulence models. The electrical current loaded in the ultracapacitor was set at the maximum current of 100 Ampere with the variation of Reynolds of 6,000, 12,000 and 24,000. It is shown that the results is slightly sensitive to the turbulence model used. The Reynolds number has significant effect towards the temperature and flow distributions around the ultracapacitors. However, for the given electricity load, the results shows that the maximum temperature around the ultracapacitor exceeds the allowable operating temperature of the ultracapacitor.