  Battery thermal management systems (BTMSs) are critical for efficient and
safe operation of lithium-ion batteries (LIBs), especially for fast
charging/discharging applications that generate significant heating within the
cell. Forced immersion cooling, where a dielectric fluid flows in direct
contact with the LIB cells, is an effective cooling approach. But because of
its complex nature, a thorough understanding of the underlying physics -
including the coupled electrochemical, thermal, fluid, and mechanical effects -
is required before immersion cooling will see wide adoption into commercial
systems. In this work, to investigate the performance of a LIB subjected to
forced immersion cooling, we develop a fully coupled modeling approach that
solves the detailed electrochemical model in conjunction with the thermal-fluid
transport models for both the cell and fluid domain. After calculating the
electrochemical and thermal responses, we also estimate the mechanical stresses
within the cell generated due to the ion diffusion and temperature rise that
impact reliability. To assess the effectiveness of forced immersion cooling, we
evaluate several different configurations for a cylindrical 18650 battery cell
under varying cell discharge rates. We compare forced immersion cooling for two
liquids (deionized water and mineral oil) at three different fluid mass flow
rates. The results highlight the strong cross-coupling of the electrochemical
and heat transfer phenomena. By comparing results across fluids and flow rates,
we define a new metric that can be used to compare the cooling capacity
considering different flow parameters. Overall, this study provides insights
that will be useful in the design of immersion cooling-based BTMSs including,
for example, the selection of forced immersion cooling specifications, such
that the temperature is controlled without significant capacity loss.
