Experimental investigation of two-phase immersion cooling of cylindrical lithium-ion cell with a low boiling point dielectric fluid

Electric vehicles (EVs) are at the forefront of sustainable transportation, requiring advancements in battery technology to enable faster charging speeds, longer lifespan, and enhanced safety. As temperature plays a critical role in the efficiency and longevity of lithium-ion cells, a key challenge to EV battery performance is effective thermal management. Elevated temperatures accelerate internal reactions, leading to faster aging, while low temperatures increase internal resistance and reduce capacity due to decreased ion mobility. With EVs operating in extreme climates and under increasing power demands, thermal management technologies must evolve to meet the growing cooling and heating requirements. This thesis explores the application of 2-phase immersion cooling as a solution to address the thermal challenges faced by EV battery packs. The study begins with a thorough review of existing research on 2-phase immersion cooling, followed by the design of an experimental setup to study 2-phase immersion cooling of a cylindrical lithium-ion cell. Experimental investigations assess the thermal performance of this cooling technique under high C-rates, with performance comparisons made between 0%, 50%, and 100% immersion of the cell. The results demonstrate significant improvements in cooling performance, with the 100% immersion case maintaining the mean cell temperature under 31.4 °C even during an aggressive 10C discharge, compared to 39.6 °C under the 50% immersion condition. However, for the 0% immersion case, the mean cell temperature exceeds the safe operational limit, reaching 88.4 °C during an 8C discharge. Dynamic testing further shows enhanced temperature stability under time-varying electric loads with 100% immersion, in contrast to the 0% immersion scenario. This research highlights the potential of 2-phase immersion cooling for improving the thermal performance of EV battery systems. Future work is outlined, focusing on cyclic ageing and battery pack level performance for this promising technology.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Tyagi, Harsh

Contributors dc:contributor

• Miljkovic, Nenad

• Electric Vehicles
• Battery Thermal Management
• Immersion Cooling
• Two-phase Heat Transfer

Statement dc:rights

• Copyright 2025 Harsh Tyagi

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130213

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130213