Details of New Energy Vehicle Technology: Power Cell Cooling System Principles
Air conditioning cycle cooling type：
The power cell unit is cooled directly by the coolant, and the coolant circulation loop and the refrigerant circulation loop are connected by the coolant refrigerant heat exchanger (the cooling unit) . Therefore, the refrigerant circulation circuit of the air conditioning system consists of two parallel branches. One for cooling the interior space and one for cooling the power cell unit. Each branch has an expansion and shut-off combination valve, and the two independent cooling systems are illustrated in the following diagram.
How cooling works:
The electric cooling fluid pump transmits the cooling fluid through the cooling fluid circulation loop. As long as the temperature of the coolant is lower than that of the battery module, the battery module can be cooled only by circulating the coolant. The increase in coolant temperature is not sufficient to keep the temperature of the battery module within the expected range.
Therefore, the temperature of the coolant must be reduced by means of the coolant heat exchanger (i. e. the cooling unit) . This is between the power battery coolant circulation circuit and the air conditioning system refrigerant circulation circuit interface.
If the expansion and cut-off combination valve on the cooling unit is opened and opened electrically, the liquid refrigerant will flow into the cooling unit and evaporate. This absorbs ambient air heat and is therefore a coolant that flows through the coolant circulation loop. The electric air conditioner compressor (EKK) compresses the refrigerant again and sends it to the capacitor, where it becomes liquid again. So the refrigerant can absorb heat again.
In order to ensure that the cooling fluid channel to discharge the heat of the battery module, the cooling channel must be evenly distributed force the entire plane of the pressure on the battery module. The compression force is generated by a spring strip embedded in a coolant channel. The spring bar is adjusted according to the geometry of the battery module and the lower part of the shell.
A spring bar of the heat exchanger is supported on a lower member of the housing of the high-voltage battery unit, thereby pressing a coolant channel onto the battery module.
Water-cooled
The water-cooled power battery cooling system uses a special coolant to flow in the coolant pipe inside the power battery to transfer the heat generated by the power battery to the coolant so as to reduce the temperature of the power battery. The following Roewe E50 electric vehicle as an example to introduce the power of water-cooled cooling system.
The cooling system makes use of the principle of heat conduction and circulates the cooling fluid in each independent cooling system loop to keep the driving motor, inverter (PEB) and power battery package at the optimal working temperature. The coolant is a mixture of 50% water and 50% organic acid technology (OAT) . The coolant must be changed regularly to maintain its optimum efficiency and corrosion resistance.
2.1. Expansion tank
The expansion tank is equipped with a pressure relief valve mounted on an inverter (PEB) tray, and the overflow pipe is connected to the outlet pipe of the battery cooler, and the outlet pipe is connected to the cooling water pipe tee. The expansion tank has“MAX” and“MIN” marks on the outside for easy observation of the level of the coolant.
2.2. Hoses
The rubber cooling fluid hose transmits the cooling fluid between each component, and the spring clamp fastens the hose to each component. The power cell cooling system (ESS) hose is located in the front compartment and under the rear floor assembly.
2.3. Cooling water pump
The cooling fluid pump of the power battery cooling system circulates the high voltage battery pack cooling system through the mounting bracket which is fixed on the chassis by 2 bolts.
2.4. Battery cooler
The battery cooler (Chiller) is a key component of the power battery cooling system, which is responsible for maintaining the power battery at an appropriate operating temperature, so that the discharge performance of the Power Battery is in the best state. The battery Chiller consists of a heat exchanger, an expansion valve (TXV) with a solenoid valve, a pipe joint, and a bracket. The heat exchanger is mainly used for the heat exchange between the power battery coolant and the refrigerant of the refrigeration system, which transfers the heat from the power battery coolant to the refrigerant.
