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We present a complete and detailed thermal simulator designed for the computational analysis of thermal batteries from the level of a single cell up to that of the entire system. Our simulator is based on a comprehensive transient and two-dimensional ͑axisymmetric͒ mathematical heat-transfer model, with significant flexibility in the geometrical modeling and the materials used. The model accounts for different aspects of heat transfer, including conduction, joule heating, heat of reactions, and latent heat of fusion associated with electrolyte phase change ͑salt solidification͒. It is supported by a simplified mass balance involving the current drawn from the battery and accounting for the mass-transfer resistance of each of the cell's components. Results presented include model verification-and-validation calculations as well as single-cell thermal battery simulations performed under realistic operating conditions. The latter reveal the significance of the phase-change process to heat transfer and thus to the prediction of its operation time. Solidification dynamics are found to be different in each of the cell's components, emphasizing the necessity of accounting for details at the subcell level. Additional results uncover the effect of heat of reactions as well as joule heating on single-cell battery thermal behavior.Thermal batteries are primary high-power-density units consisting of serial-connected and thermally insulated cells. These moltensalt-based batteries supply electrical power for many autonomous devices in need of large currents and instantaneous ignition. 1 The integration of a high-temperature molten salt within the cells enables fast ion transfer, guaranteeing superior electrical performance. However, due to the required high operational temperatures ͑300-700°C͒, thermal-battery operation time is often governed by heat loss to the surroundings.Thermal design, leading to a delay in the onset of salt solidification, is therefore of utmost importance. The design process includes optimization of the geometrical arrangement, cell structure, and thermal insulation materials. Developing a battery meeting required performance specifications and constraints, using rules-of-thumb together with trial and error experiments, can become an inefficient process in terms of time and costs. The process of developing and optimizing each thermal battery design may be considerably enhanced by using battery-performance simulations based on a valid and well-calibrated mathematical model.Thus far, battery-performance simulation efforts have mostly been invested in single-cell modeling. Mass-transport equations for a binary molten-salt mixture were presented, 2,3 followed by a transient mass-transfer-electrochemical mathematical model for a single cell. 4 The latter ͑solved in one dimension across the cell͒ involved two porous electrodes and a separator, saturated with a molten salt ͑LiCl-KCl͒ electrolyte, and was also supported by a lumped heattransfer model. This modeling approach was further developed 5 and then expa...

We present numerical simulations of three-dimensional liquid bridges between two identical smooth and chemically homogeneous cylinders held at a fixed distance and angle one with respect to the other. Despite the limited range of parameters studied, an analysis of resultant forces, energies, and torques reveals a rich level of detail. For large enough separations between the cylinders, the bridges appear symmetric and stable in shape and are found to yield a negligible torque on the cylinders. The force of adhesion is found to be positive in this case (the cylinders are attracted one to the other). A reduction in the distance between the cylinders reveals different behavior depending on the particular value of the set of parameters considered. For example, it appears that while relatively low contact angle systems favor attractive (positive) forces and stable symmetric bridges for small separation distances, larger contact angles lead to the coexistence of stable asymmetric and (apparently) unstable symmetric solutions, mostly (and respectively) associated with near-zero and negative (repulsive) forces of adhesion. In addition, while the larger values of contact angles studied here (90 degrees, 110 degrees) are associated with barely detectable torques, smaller values of contact angle are found to be associated with torques acting to rotate cylinders into a position where they are parallel one with respect to the other.

We present the application of our thermal battery system-level simulator [J. Electrochem Soc., 156, A442 (2009)] in novel multiplecell thermal analyses. Several model batteries are chosen to demonstrate the simulator's versatility and robustness in developing advanced thermal battery designs. The heat transfer phase-change model and supporting mass balance are modified to improve model consistency. Simulation results are presented from several case-studies covering different battery structures and operating conditions, including low and high current densities, different number of electro-active cells, various internal and external battery geometrical details, the use of salt buffers, external flanges, and inhomogeneous initial conditions in the battery stack. These results show the simulator to be a highly user-friendly and powerful tool for development of complex thermal batteries. Investigation of heat of reactions and joule heating effects unfold insights regarding dominant processes in multiple-cell batteries. Furthermore, these detailed analyses emphasize the need to track solidification dynamics at the sub-cell level and, at the same time, show that thermal battery design should include a significant ingredient of multiple-cell analysis. Altogether, this study presents a first-in-itskind portable simulator with great flexibility and a capability for supporting the analysis and development of most thermal battery structures and designs.