Session: 10-01: Photovoltaic, Photovoltaic-Thermal, and Electrochemical Technologies I

Paper Number: 156852

156852 - Computational Investigation of Using Micro-Encapsulated Phase Change Material in Direct Liquid Cooling of a Lithium-Ion Battery 

Abstract: 

Lithium-ion batteries (LIB), due to their high energy density, operating efficiency, and long cycle life, are vital to the success and efficacy of electric vehicles (EV). However, the performance of LIBs is sensitive to temperature. Generally, for optimal efficiency and lifetime, LIBs should be operated at a temperature between 15-35℃ with a maximum temperature difference across a cell or module of less than 5℃. As such, the battery thermal management system (BTMS) is essential to support safe and efficient operation of EVs, and improvements to the BTMS are important to improve the lifecycle and efficiency of LIBs. BTMS can be categorized by how it cools the batteries. Common approaches include air cooling, indirect liquid cooling, and direct liquid cooling. Phase change materials (PCM) have also been investigated for this application and have shown promise due to their capability of absorbing significant amounts of thermal energy without a change of temperature. Typical approaches have focused on surrounding the cells with PCM or a PCM-composite material. This study investigates a new approach of using micro-encapsulated phase change material (MEPCM) in the liquid used for direct liquid cooling of a battery. A numerical model of a direct, liquid cooled lithium-ion cell was developed. The battery electrochemical behavior was modeled using a multi-series, multi-domain equivalent circuit model (ECM) to represent a Lithium Nickel Manganese Cobalt Oxide (NMC) cell. The flow of a dielectric liquid around the cell and the heat transfer from the cell to cooling fluid was modeled by solving the governing momentum and energy equations. A hydrofluoroether (HFE) dielectric fluid is modeled. The phase change of the MEPCMs in the fluid was modeled using the effective specific heat capacity method. A series of simulations were performed to determine the effect of the MEPCM on the electrical behavior, average temperature, temperature distribution of the cell, and pressure drop across the cell during a constant current discharge. The study investigates the percent weight of MEPCM in the dielectric, the temperature range over which melting occurs (melt window), and inlet velocity. The results indicate that adding even 5 wt% MEPCM to an active, direct liquid cooling system can provide a desirable drop in temperature rise of a LIB during discharge. Additionally, the addition of MEPCMs to the fluid does not result in a significant increase in pressure drop and therefore parasitic power consumption. The study also indicates, when melting of the MEPCM occurs, lower inlet velocities can be used to limit the battery temperature rise.

Presenting Author: Jackson Nagel North Dakota State University

Presenting Author Biography: Jackson Nagel is currently pursuing a M.S. in Mechanical Engineering at North Dakota State University with a focus on electric vehicle battery thermal management systems. He received his Associates in Science from Bismarck State College in 2019 and worked as Field Engineer in the solar industry for 1.5 years. Returned to academia and finished his Bachelor of Science in Mechanical Engineering at North Dakota State University in 2023. During his time in his undergraduate career at North Dakota State University he worked as an undergraduate research assistant under Dr. Adam C. Gladen.