Session: 11-03-01: Heat Transfer in Batteries and Energy Storage Technologies

Paper Number: 97123

97123 - CFD and Experimental Investigation of Graphite Heat Spreader Based Cooling for Li-Ion Batteries for Electric Vehicles and EVTOL (Electric Vertical Take-Off and Landing) Aircraft Applications 

Over the past few years, owing to different critical features such as high energy densities, safety, cycle-life etc., Lithium-ion batteries have been used aggressively and successfully as an energy storage system for automotive applications. In addition, due to recent increase in interests towards developing eVTOL aircrafts, demand for Li-Ion batteries capable of providing high power discharge and charge along with above mentioned features has risen. Thermal Management System is a critical component of a Li-Ion battery system that enables sustained high-power peak performance, improves overall life-cycle, and reduces possibility of thermal runaway during regular vehicle operation. The current article studies two different cooling configurations for thermal management of a commercially available 9 A-h Nickel Manganese Cobalt (NMC) Lithium-ion pouch cell for high C-rate conditions. The two configurations are referred to as the Double-sided cooling and Hybrid cooling, which includes a novel approach utilizing graphite-based heat spreader. The thermal performance for both configurations are studied through experimental testing and CFD (computational fluid dynamics) modeling. During experimental analysis, the pouch cell was subjected to high C-rate discharges of 3C, 4C and 5C using an Arbin controller and thermal test bench including a cold plate, mass flow meter, and temperature sensors. The temperature response of the cell is measured using T-type thermocouples that are strategically installed on its surface using a thermal interface material. For the numerical analysis, time-accurate, conjugate heat transfer-based 3D CFD simulations are conducted on high spatial resolution grids with commercially available finite-volume method based CFD software, STAR-CCM+. Numerical simulations at the mentioned C-rates are then run to explore the overall temperature distribution on the cell body. Temperature estimates from the numerical model are compared to the test data for the most aggressive 5C discharge condition. Both experimental testing and numerical modeling show that the Hybrid cooling approach provides higher rate of heat transfer compared to Double-sided cooling, owing to high thermal conductivity of graphite. Average cell surface temperatures using Hybrid cooling are ∼3°C, 3.7°C and 4.3°C lower than Double-sided cooling for 3C, 4C and 5C discharge conditions, respectively. The maximum measured cell temperature at the end of the most aggressive 5C discharge is 6°C lower in the case of Hybrid cooling. The temperature gradients are also less aggressive thereby allowing for a more uniform temperature distribution within the cell. Additional results in terms of velocity distribution and pressure drop are also provided for the cold plate present in the cooling setup.

Keywords: Li-Ion Battery, Pouch Cell, Electric Vehicle (BEV, PHEV, HEV), eVTOL, CFD, thermal modeling, STAR-CCM+

Presenting Author: Prahit Dubey Romeo Power Technology

Presenting Author Biography: Dr. Prahit Dubey is working as the Direction of Battery Modeling, Thermal Engineering, and Systems Integrity at Romeo Power, which is premium battery pack manufacturer for automotive applications. Prior to joining Romeo, he worked at Siemens PLM, Dresser-Rand and IBM. Dr. Dubey obtained his PhD in Mechanical Engineering (CFD and Thermal Science) from University of Cincinnati under professor Dr. Urmila Ghia.

Authors:

Shashwat Bakhshi Romeo Power
Prahit Dubey Romeo Power Technology