TY - JOUR A1 - Voigt, Sascha A1 - Sträubig, Felix A1 - Palis, Stephan A1 - Kwade, A. A1 - Knaust, Christian T1 - CFD-analysis of Sensible Enthalpy Rise Approach to determine the heat release rate of electric-vehicle-scale lithium-ion batteries N2 - This paper analyses the suitability of the Sensible Enthalpy Rise Approach for measuring the heat release rate of electric-vehicle-scale lithium-ion batteries. An apparatus is designed that meets the conditions of an electric-vehicle-scale lithium-ion battery fire by using cement board as wall material. Modifications of the Sensible Enthalpy Rise Methodology are presented due to the high emissivity and inhomogeneous temperature distribution of the apparatus wall material: a power 4 approach for the heat flow from the walls to the ambient air and an alternative determination methodology for the wall temperature. A one factor at a time parameter study is performed with Computational Fluid Dynamics simulations, investigating a new calibration method based on a fit approach compared to common methods, the wall temperature determination, the approach for the ambient heat flow, the calibration power and the volume flow at the outlet. The simulations show, that suitable estimations of the heat release rate are obtained by using the modifications for wall temperature determination and the power 4 approach for the ambient heat flow. The three calibration methods provide suitable constants, if the calibration power in the same order of magnitude as the mean of the heat release rate profile of the test object. KW - Lithium-ion batteries KW - Heat Release Rate KW - Calorimetry KW - Sensible Enthalpy Rise Approach KW - Computational Fluid Dynamics PY - 2020 U6 - https://doi.org/10.1016/j.firesaf.2020.102989 VL - 114 SP - 1 EP - 14 PB - Elsevier Ltd. AN - OPUS4-50964 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Voigt, Sascha A1 - Sträubig, Felix A1 - Kwade, A. A1 - Zehfuß, J. A1 - Knaust, Christian T1 - An empirical model for lithium-ion battery fires for CFD applications N2 - Lithium-ion batteries are a key technology to achieve the goals of limiting climate change due to the important role as traction technology for Electric Vehicles and in stationary energy storage systems. Over(dis) charge, mechanical damage due to accidents or thermal abuse such as fires can initiate an accelerated self-heating process of the batteries, called thermal runaway. A thermal runaway can propagate from cell to cell within a larger assembly of cells such as modules or battery packs and can cause rapid heat and toxic gas emissions. The resulting battery fire can spread to adjacent facilities, e.g. other cars in underground car parks or to a whole building in case of a large stationary energy storage. For proof of fire protection requirements or to design suitable fire protection systems, Computational Fluid Dynamic (CFD) simulations are getting more and more important. The aim of CFD fire simulations is to predict the global hazards of a fire to its surroundings, that is mainly characterized by the release of heat and smoke and its spread in the fire environment. There are many numerical investigations of lithium-ion batteries in the literature. One class of models is used to simulate the charge and discharge process of lithium-ion batteries and to predict the temperature or voltage evolution inside the battery. On the other hand, there are models describing batteries under abuse conditions to predict the consequences of a thermal runaway event to the local environment, like the temperatures inside a battery or at the battery surface. Henriksen et al. use a generic battery gas mixture to simulate an explosion of vented gases from a Lithium Iron Phosphate battery and compare experimental results for the explosion pressure and the position of the flame front to the outcomes of a simulation with Xifoam. Larsson et al. used a combination of CFD simulations with FDS and thermal model with COMSOL to predict the temperature development of neighboring cells in a thermal runaway propagation. Truchot et al. use a design Heat Release Rate (HRR) curve for a battery based on experimental measurements to build up an overall HRR curve for a truck loaded with 100 lithium-ion batteries. This summed up HRR and corresponding smoke production curve is then used as an input for a simulation of a truck fire in a tunnel with Fire Dynamics Simulator (FDS). The pre-definition of the HRR curve is a frequently used method in fire engineering. It has the disadvantage, that the heat release cannot be influenced by physical processes, such as changed ventilation conditions or extinguishing measures. In this paper, a model is presented that determines the release of heat and gases based on the thermal runaway mechanisms of the battery, which can be used in CFD fire simulations with focus on prediction of fire hazards to nearby environment. KW - Lithium-ion battery KW - Battery fires KW - Computational Fluid Dynamic (CFD) KW - Empirical model PY - 2023 U6 - https://doi.org/10.1016/j.firesaf.2022.103725 SN - 0379-7112 VL - 135 IS - 135 SP - 1 EP - 12 PB - Elsevier Ltd. AN - OPUS4-57347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Voigt, Sascha A1 - Sträubig, Felix A1 - Palis, Stephan A1 - Kwade, A. A1 - Knaust, Christian T1 - Experimental comparison of Oxygen Consumption Calorimetry and Sensible Enthalpy Rise Approach for determining the heat release rate of large-scale lithium-ion battery fires N2 - From a fire safety point of view, the burning behavior of lithium-ion batteries is of high interest. The heat release rate (HRR) is the most important fire parameter to analyze the fire hazards of burning objects, so that an accurate determination of it is crucial. In this paper, two different measurement techniques, the Oxygen Consumption Calorimetry (OCC) and the Sensible Enthalpy Rise Approach (SERA) are simultaneously performed in the same calorimeter to measure the HRR of two different types of lithium-ion batteries. HRR values as well as total energies determined by SERA are higher than measured with OCC: The total energy released is about 10–12 times (SERA) and 6–9.5 times (OCC) the electrical stored energy for both battery types, whereas the timescales of the release differ strongly between the types, resulting in maximum HRRs of 3.4 MW (SERA) and 1.5 MW (OCC) for one module of type A and 0.8 MW (SERA) and 0.6 (OCC) of type B respectively. Furthermore, a sensitive dependency of the HRR measurement with SERA on the position of the wall temperature measurement is observed. KW - Fire tests KW - Lithium-ion-batteries KW - Heat release rate KW - Calorimetry KW - Sensible enthalpy rise approach KW - Oxygen consumption calorimetry PY - 2021 U6 - https://doi.org/10.1016/j.firesaf.2021.103447 SN - 0379-7112 IS - 126 PB - Elsevier Ltd. AN - OPUS4-53441 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -