What are the heat dissipation methods of the power cell module?

At present, there are many discussions on liquid cooling and phase transition material cooling. Tesla is typical of the cylindrical core liquid cooling module and will be introduced in the following example. A simple liquid-cooled system is to place a well-conducting device close to the core and remove the excess heat generated during the core operation as evenly and efficiently as possible.

Liquid cooling can be completely independent like Tesla, or it can be combined with other cooling methods. One of the important forms is to combine with thermal conductive silica gel. Thermal conductive silica gel can obtain a closer bonding than metal contact metal, and thus obtain better heat transfer performance.

Introduction of Heat Extraction Mode of power battery Module

The heat generated during the operation of the core is transmitted to the liquid-cooled pipe through the heat-conducting Silicon gel gasket, and the heat is carried away by the hot expansion and cold contraction of the coolant free circulation flow, so that the temperature of the entire battery pack is uniform and the coolant is strong. The heat generated by the heat absorption core during the operation, Enables the entire battery pack to operate at a safe temperature. The thermal conductive silica gel has good insulation performance and high elastic toughness, which can effectively avoid the problem of vibration and friction damage between the electric cores, and the potential short-circuit danger between the electric cores. It is the best auxiliary material for the water-cooling scheme.

This liquid cooling scheme adopts S-type heat conducting aluminum tubes and attaches a different type heat conducting Silicon tape to the aluminum tube(adding raised stripes to the contact surface between the heat conducting Silicon tape and the core) to allow the contact surface between the core and the heat conducting tube. Bigger, better thermal conductivity and shock absorption effects.

The battery module PCM heat dissipation structure of the cylindrical battery, the application of phase transition materials, can be combined with liquid cooling, or can be used independently. Independent applications can have a variety of arrangements. The PCM sheet can be affixed to the outside of the battery module to assist in heat dissipation. According to the experimental results, the existence of phase transition materials can also play a cooling role.

The most efficient way is naturally the way in which the core and PCM come into contact with the largest area. Examples are as follows.

Phase transition materials are used for heat management batteries. The quality of the required PCM is first calculated, the geometric size of the matrix of the phase transition material is determined according to the shape of the cell, the matrix of the phase transition material is made, and the hole with the same size as the single cell is evenly dug out on the matrix., The number of holes is determined by the number of individual batteries that can be accommodated in the battery module.

The application of this form of phase transition material objectively prevents the transmission of heat runaway monomer energy and is considered to be an ideal form of heat management.

The basic requirements of the power cell application scenario for phase transition materials:

The phase transition temperature is low, and it needs to adapt to the optimal operating temperature range of lithium batteries 15 °C -35 °C;

The material phase transition temperature can be adjusted in a small range, and the optimal operating temperature range of different types of cores is not exactly the same;

It is best to avoid the appearance of liquid gaseous phase before and after the phase transition.

If the material has high latent heat, the system has strong temperature.

The heat transfer coefficient must be high in order to maintain a uniform temperature;

Material insulation is good to avoid the high voltage system insulation leakage risk.

The low mass density of the phase transition material decreases the effect on the energy density of the battery pack.

Even if the above conditions are met, the application of phase transition materials still has limitations. When the environment is extremely harsh, such as high temperatures. The ability of the phase transition material to absorb heat is limited. When the phase change is completed, the system temperature naturally rises. When the temperature is too low and too low for a long time, the cold start of the vehicle must absorb external energy to heat it.

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