Lithium-ion (Li-ion) batteries are currently considered as vital components for advances in mobile technologies such as those in communications and transport. Nonetheless, Li-ion batteries suffer from temperature rises which sometimes lead to operational damages or may even cause fire. An appropriate solution to control the temperature changes during the operation of Li-ion batteries is to embed batteries inside a paraffin matrix to absorb and dissipate heat. In the present work, we aimed to investigate the possibility of making paraffin nanocomposites for better heat management of a Li-ion battery pack. To fulfill this aim, heat generation during a battery charging/discharging cycles was simulated using Newman’s well established electrochemical pseudo-2D model. We couple this model to a 3D heat transfer model to predict the temperature evolution during the battery operation. In the later model, we considered different paraffin nanocomposites structures made by the addition of graphene, carbon nanotubes, and fullerene by assuming the same thermal conductivity for all fillers. This way, our results mainly correlate with the geometry of the fillers. Our results assess the degree of enhancement in heat dissipation of Li-ion batteries through the use of paraffin nanocomposites. Our results may be used as a guide for experimental set-ups to improve the heat management of Li-ion batteries.
Compared to the commonly employed finite element models of RC structures in earthquake engineering, based on structural elements, refined finite element models, characterized by discretizing the concrete by 3D continuum elements together with an advanced nonlinear material model for concrete combined with 1D truss elements for the reinforcement together with an elastic-plastic material model for steel, allow valuable deeper insights into the stress distribution in RC structures and the evolution of concrete damage. As a first step towards the application of such refined finite element models in earthquake engineering, their capabilities and shortcomings are demonstrated for pushover analyses. For this purpose, pushover analyses of four RC frames were performed, for which well documented extensive test data from shaking table tests, conducted by Yavari, is available. The comparison of numerical and experimental results demonstrates the capability of refined FE-models to capture the lateral load carrying capacity as well as the location and evolution of concrete damage very well. However, the well-known shortcoming of pushover analyses of predicting a much larger lateral ductility compared to the observed one in the shaking table tests was also observed.
Rechargeable lithium-ion batteries (LIBs) are now playing crucial roles in power supply and energy storage systems. Among all types of rechargeable batteries available nowadays, LIBs are one of the most important ways to store energy because of their high energy density, high operating voltage, and low rate of self-discharge. Nonetheless, the performance of LIBs could be improved by different design parameters, such as the size of solid particles in the battery composite electrodes. Therefore, this study aims to investigate the effect of the composite electrode particles size on the electrochemical and heat generation of an LIB. A Newman's electrochemical pseudo two-dimenisonal model was used to model the LIB cell. Reversible heat produced through electrochemical reactions was calculated as well as irreversible heat originating from internal resistances in the battery cell. Our results show that smaller sizes of electrode solid particles improve the thermal characteristics of the battery, especially in higher charge and discharge currents (C-rate). Furthermore, as the solid particle sizes decrease, the battery capacity increases for various C-rates in charge and discharge cycles.
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