Battery Power - September/October 2013 - (Page 6)

Feature Thermal Management of an Electrical Vehicle Battery Packing Using 1D and 3D CFD Doug Kolak, Boris Marovic and Steve Streater Mentor Graphics With the increased concerns over the future use of fossil fuels, especially in automobiles, the rise of popular sentiment towards electric and hybrid electrical vehicles is no surprise. But there is still a major area of design challenge: batteries. As the primary means for storing the electrical energy used for electrical vehicles, the battery of choice needs to be extremely efficient yet as lightweight as possible to allow for reasonable driving distance on a single charge. Although several factors affect the efficiency of these batteries, one of the most important is temperature. Batteries usually have a low margin for the temperatures in which they work best. If a battery is exposed to excess heat for too long, it will likely fail; on the other hand, when the battery is too cold, it is unable to operate efficiently. This poses two design challenges that are essential to overcome when looking at electrical vehicle batteries. First, the cooling pack of the battery must be designed in a way that allows excess heat to be removed quickly and efficiently from the battery cells. And second, the thermal control system for the battery must be able to warm the battery to an efficient temperature level in a reasonable amount of time for good performance. With the lack of an internal combustion engine in electrical vehicles, this becomes crucial in the parts of North America, Europe and Asia where the temperature can reach well below freezing in winter. With the ever shortening time constraints on auto manufacturers today, how can these system go through the numerous time consuming design iterations necessary for a best-in-class, reliable design? Simulating with 1D and 3D Computational Fluid Dynamics As engineers continue to face these challenges, they need to be able to leverage all available tools to design the safest and most reliable product that is both efficient and inexpensive to produce. In the last few decades, the area of virtual prototyping has continued to grow as the suite of digital tools expanded. One of the most common engineering software tool options available is computational fluid dynamics or CFD software. CFD is an area of fluid mechanics that uses computer-based engineering calculations to model and simulate the behavior of a liquid or gas within mechanical or electrical systems and the heat transfer throughout the model. The use of CFD to simulate the 6 Battery Power • September/October 2013 flow and heat transfer of a design means information for all variables at all locations, and if necessary at every moment in time, can be recorded instead of at a limited number of discrete points as with physical testing. These results can give a more complete picture of the behavior of a component or design, which gives a large scope to understand behavior that isn’t quite as expected. Over the years, different types of CFD software have been developed, including one-dimensional (1D) and three-dimensional (3D) options. Both of these solutions have been used successfully for modeling thermo-fluid systems in many industries, especially the automotive industry. Both 1D and 3D CFD enable engineers to improve their understanding of fluid flow and engineering designs and in many organizations, both are used to improve product and system design and to ensure performance targets are achieved throughout the operating cycle of interest. When engineers have access to multiple options for CFD analysis, the question arises, “When to use 1D CFD versus 3D CFD?” Although there is no definitive answer, the strengths and weakness of each approach lend themselves to two fairly defined segments. When designing a single component or small sub-set of components, every inch of length or degree of curvature can make the difference between efficient operation and undesired fluid flow. In these cases, where small changes to a single part of a system are crucial or there are significant flow variations in multiple dimensions, 3D CFD is the obvious choice because of its ability to analyze complex geometry with extreme accuracy. However, these benefits come with drawbacks, which become more evident as the scale of the design increases. When the design reaches beyond the component level into a large system of interconnected components by pipes, ducts and hoses, the computation requirements can become too high and simulations take too long to fit within development schedules. When this occurs, 1D CFD is a good choice. Because the 1D approach simplifies the 3D geometry to the component level, usually characterized by some sort of performance data, this type of analysis uses much less computing power and is usually significantly faster than a comparable 3D model. One of the biggest challenges with 1D CFD modeling is getting performance data that can adequately define the 3D geometry of the component at the system level. This has historically been done in one of several ways, including data from a supplier, physical testing or empirical data from text books that is often available for standard geometries such as bends and junctions. Although these methods are adequate, it can often be time consuming to wait for a supplier to provide data; and one of the main goals of virtual prototyping is to understand the system before physical testing. With this information, how best can 1D and 3D CFD be applied to electrical and hybrid vehicle battery design? www.BatteryPowerOnline.com http://www.BatteryPowerOnline.com

Table of Contents for the Digital Edition of Battery Power - September/October 2013

ABB to Build World’s Largest Network of EV Fast-Charging Stations in the Netherlands
Duracell Powermat and Starbucks Expand Wireless Charging in Silicon Valley Area
Thermal Management of an Electrical Vehicle Battery Packing Using 1D and 3D CFD
New Battery Technologies - Added Value Electronics Can Turn Normal Batteries into Smart Battery Packs
A Novel Single-Compartment Concentration Cell Driven by Natural Evaporation for Green Energy Harvesting
Highly Accurate Li-Ion Battery Simulation
Batteries
ICs & Semiconductors
Charging, Testing & Monitoring
Industry News
Marketplace
Application Profile

Battery Power - September/October 2013