Experimental studies of a static flow immersion cooling system for fast-charging Li-ion batteries

ABSTRACT

This study explores the performance of a steady-state flow single-phase non-conductive liquid immersion cooling system in a single-cell Li-ion battery under a variety of thermal environments such as 25°C, 40°C, and 60°C and tested at different charge C-rates. The experimental results show that the proposed cooling system exhibited the best cooling performance of less than 5°C and a significant temperature rise reduction of 34% at 3C rate under the ambient temperature of 25°C. Also, it provided uniform temperature distribution within the cell when charged at fast charge rates of 2C and 3C operations.

KEYWORDS:

• Battery thermal management system
• Li-ion battery
• temperature distribution
• Battery thermal gradient
• fast charging

Nomenclature

$C_p$	=	Cell specific heat capacity (J/kgK)
${\dot{Q}}_d$	=	Heat dissipation rate (W)
h	=	Convective heat transfer co-efficient for free air (W/m2 K)
$T_a$	=	Ambient Temperature (oC)
$T_s$	=	Cell surface Temperature (oC)
A	=	Surface Area of cell (m2)
L	=	Characteristic length (Volume of cell/Area of cell)
$K$	=	Thermal Conductivity (W/mK)
$\left(T_s-T_a\right)$	=	Temperature difference between battery surface and ambient temperature (oC)
$K_f$	=	Thermal conductivity of the fluid (W/mK)
$C_{p,f}$	=	Specific capacity of the fluid (J/kgK)
${\rho }_f$	=	Density of the fluid (kg/m3)
$T_f$	=	Fluid temperature (oC)
µ	=	Dynamic viscosity of the fluid (Ns/m2)
$\vec{V}$	=	Velocity vector
g	=	Gravitational acceleration (9.81 m/s2)
β	=	Coefficient of volume expansion of the fluid (K−1)
$\mathrm{\Delta }{\mathrm{T}}_f$	=	Temperature difference between mean temperature of battery system and ambient temperature in immersion cooling (oC)
$h_f$	=	Convective heat transfer co-efficient for fluid (W/m2 K)
${\dot{Q}}_{df}$	=	Rate of Heat transfer by convective dielectric fluid flow (W)
Nu	=	Nusselt number
Pr	=	Prandtl number
Ra	=	Rayleigh number
Gr	=	Grashof number
∆T	=	Difference in temperature rise between battery and ambient in natural air convection cooling (oC)
dT/dt	=	Rate of change of battery temperature (oC/min)
T1	=	Negative tab temperature (oC)
T2	=	Positive tab temperature (oC)
T3	=	Battery body temperature (oC)
T4	=	Fluid temperature far from battery surface (oC)

Abbreviations

BTMS	=	Battery thermal management system
EVs	=	Electric Vehicles
HEVs	=	Hybrid Electric Vehicles
C-rate	=	Current rate
NACC	=	Natural air convection cooling
CC-CV	=	Constant current-Constant voltage
SFIC	=	Static flow of immersion cooling

Acknowledgments

Author wishes to express her gratitude thanks to the CSIR - Centre for Electrochemical Research Institute for the extensive support. ‘Council of Scientific and Industrial Research’ provides financial support for this project.

CSIR-CECRI manuscript communication number

CECRI/PESVC/Pubs/2023-055

Disclosure statement

No potential conflict of interest was reported by the authors.