On The Choice of Liquid Cooling Heat Transfer Media

The choice of heat transfer medium has a significant impact on the performance of the liquid-cooled thermal management system and the heat transfer medium should be determined prior to the design of the thermal management system.
Direct contact liquid cooling uses electrically insulated liquids with high thermal conductivity (e.g. silicone based oil, mineral oil) in direct contact with the single cell or module, which can well solve the problem of module temperature homogenisation, but as the insulating liquid is usually relatively viscous, the flow rate will not be very high, thus limiting its heat exchange effect. and the way in which the fluid flows through the cell.

In the case of the liquid cooling plates and serpentine bends we have at Trumonytechs, for example, in indirect contact liquid cooling, the fluid flows inside the pipe and comes into direct contact with the battery through the thermal conductivity interface material, for example, transferring heat through the thermal conductivity interface material and cooling the battery by transporting it through the fluid flow heat exchanger.
As there is no insulation requirement and no flow rate restriction, liquids with high thermal conductivity but poor insulation can be used and the heat transfer effect is very good. However, the temperature uniformity is somewhat worse than with direct contact liquid cooling. In order to prevent leakage causing a short circuit, this method has higher requirements for the sealing of the pipes. The main heat transfer media generally chosen are water, glycol, silicone, paraffin, etc.

Regardless of the type of liquid cooling system used, one problem is that there are gaps between the battery cells and the arrangement piping or the jacket around the module arrangement, and air is an undesirable medium for heat transfer, where thermal conductive silicone sheets can eliminate this obstruction to heat transfer.