Heat pump type integrated thermal management system
1. Heat pump type integrated thermal management principle
On the basis of integrated thermal management systems, in order to better meet the high temperature sensitivity of batteries, the complexity and refinement of thermal management of pure electric commercial vehicles continues to increase, and some innovative applications are being added, such as heat pumps Technology is one of them. The heat pump itself does not produce heat, but is just a transporter of heat. Based on the principle of the reverse Carnot cycle, it uses a small amount of electric energy to drive the unit, circulates the working medium in a disguised phase, and absorbs, compresses, and heats low-grade heat energy before utilizing it. The main components of a heat pump include refrigerant, compressor, condenser, expansion valve and evaporator. It is a closed loop in which the medium, the refrigerant/refrigerant, is continuously compressed and expanded in the loop. Each time it is compressed and expanded (that is, each cycle of operation), the refrigerant "extracts" heat from the low-temperature environment and transfers it to the high-temperature environment. Air is not used as a refrigerant, although it does not cause pollution and is cost-free, because its thermal efficiency per cycle is quite low. The actual refrigerant used is a liquid that evaporates when absorbing heat and condenses when dissipating heat. The process of changing the liquid form can greatly improve the thermal efficiency in each working cycle. The heat pump system has two working modes: cooling and heating. By integrating heat pump technology with integrated thermal management systems, new heat pump-type integrated thermal management systems can be developed. The heat pump air conditioning system using this technology uses an electric air conditioning compressor and utilizes the reversible characteristics of the refrigeration cycle to integrate refrigeration and heating. It has the advantages of good versatility, compact structure, high efficiency, energy saving and environmental protection, and has become a new type of vehicle air conditioner. trend. Under winter heating conditions, the COP (Coefficient of Performance) can reach 2 to 4. The energy efficiency is many times that of the PTC heating system commonly used in the field of pure electric vehicles, which can effectively extend the driving range by more than 20%. The current types of heat pump systems mainly include direct heat pump air-conditioning systems, indirect heat pump air-conditioning systems and air-supplementing and enthalpy-increasing direct heat pump air-conditioning systems, which can be used for heating and cooling. In layman's terms, the use of a four-way reversing valve in a heat pump system can interchange the functions of the evaporator and condenser of the heat pump air conditioner and change the direction of heat transfer, thereby achieving the effect of cooling in summer and heating in winter.
2. Experimental verification of heat pump integrated thermal management
At present, heat pump-type integrated thermal management systems are rarely used in pure electric commercial vehicles, and there are some applications in passenger vehicles. The heat pump system converts the heat in the air into its own internal energy through the gas-liquid conversion of the refrigerant. The COP value is 2 to 3 times higher than that of the PTC heating system, which can effectively extend the driving range by more than 20%, even at extremely low temperatures. temperature, the COP can still be guaranteed to be greater than or equal to 1, while the PTC energy efficiency coefficient is generally less than 1. In the heating process, the heat energy of the outside air is forcibly transferred to the air conditioning system of the passenger compartment by relying on the reverse circulation of the system. Therefore, the energy efficiency coefficient of heat pump air conditioning is 2 to 3 times higher than that of PTC heating.
