Computational fluid method (CFD) is popular in either large-scale or meso-scale simulations. One example is to establish a new pore-scale (m~μm) model of laboratory-scale sediment samples for estimating the dissociation rate of synthesized CO2 hydrate (CO2H) reported by Jeong. It is assumed that CO2H formed homogeneously in spherical pellets. In the bulk flow, concentration and temperature of liquid CO2 in water flow was analyzed by CFD method under high-pressure state. Finite volume method (FVM) were applied in a face-centered packing in unstructured mesh. At the surface of hydrate, a dissociation model has been employed. Surface mass and heat transfer between hydrate and water are both visualized. The initial temperature 253.15K of CO2H pellets dissociated due to ambient warm water flow of 276.15 and 282.15K and fugacity variation, ex. 2.01 and 1.23 MPa. Three tentative cases with porosity 74, 66, and 49% are individually simulated in this study. In the calculation, periodic conditions are imposed at each surface of packing. Numerical results of this work show good agreement with Nihous’ model. Kinetic modeling by using 3D unstructured mesh and CFD scheme seems a simple tool, and could be easily extended to determine complex phenomena coupled with momentum, mass and heat transfer in the sediment samples.
Part of the book: Heat and Mass Transfer
To ensure electrical safety and reliability in electric vehicles equipped with a high-voltage battery pack, an insulation monitoring circuit is indispensable to continuously monitor the insulation resistance during charging or driving. Existing methods such as injecting specific signals into the monitoring circuit and earth help to extract the resistance value from the voltage waveform. However, parasitic or stray capacitances in the monitoring circuit, which might introduce higher order dynamics into the waveform, are ignored. To avoid estimation error, the insulation resistance must be known in advance to carry out parameter calibration. In this chapter, one parasitic capacitance is applied in the circuit model and a new adaptive algorithm based on Lyapunov stability is employed to estimate the insulation resistance. This new online monitoring method and circuit are verified through simulation and experimentation, respectively. The results demonstrate that the proposed method can quickly react and track variations of insulation resistance on both positive and negative direct current (DC) lines.
Part of the book: New Trends in Electrical Vehicle Powertrains
For stabilizing renewable energies and shaving peak power at noon, both the energy consumption and potential renewable energies in Dihua waste water treatment plant (WWTP) in Taiwan are analyzed. Under the consideration of environment, cost, and performance, automotive reused lithium-ion battery (RLIB) is employed. Two typical automotive lithium-ion batteries are used in this study after the selection of suitable battery cells. In particular, one simple, converterless energy management system (EMS) is developed and integrated in new RLIB packs. The control strategy between RLIB and an additional physical battery is adjusted by simulation. An online estimation of RLIB’s internal resistance and open-circuit voltage monitoring scheme is applied in EMS to ensure the safety of RLIB. The bench test and rough economical estimation reveal that EMS shows great potential in elongating life cycle and possibly benefits from feed-in tariff and peak shift of electricity charges.
Part of the book: Energy Systems and Environment