Feasibility study of PTC electric heater in automobile air-conditioning products

At present, the electric heaters used in automobile air-conditioning products are mainly PTC electric heaters and electric heating tube heaters. At this stage, the popularity of PTC electric heaters is very fast, and has gradually replaced electric heating tube heaters. The main feature of the PTC heater is that it can change the amount of heat, and then adjust the temperature in the car to achieve the effect of rapid heating. At the same time, it can also allow the air conditioner to operate normally in some colder areas. 1 　 Overview of PTC electric heater The above analysis of the main properties of the metal electric heating tube, there are certain safety hazards, in the limited structural space inside the car, due to the limited power, the maximum rated power will not remain too high under the normal state , But if it is in a dry state, it is extremely prone to redness. Therefore, in order to improve the heating effect of automobile air-conditioning products, ceramic PTC electric heaters can be used. PTC electric heaters mainly use PTC thermistor elements as heat sources for heating. The thermistor in the PTC electric heater is usually made of semiconductor materials. Its resistance can change rapidly with the temperature. At the same time, when the external temperature gradually decreases, the resistance of the PTC will also decrease, and the heat It will also increase, among which ceramic PTC electric heaters have higher power. According to the changes in the characteristics mentioned above, PTC electric heaters have the characteristics of energy saving, safety, stability and long life. They have strong adaptability in automotive air-conditioning products and have been widely used in household appliances and industrial electric appliances. . At present, the application of PTC electric heaters in automobile air-conditioning is already in the promotion stage abroad, but in the R&D and production stage in China. For pure electric vehicles, the current pure electric vehicles used are PTC wind heating. This method only needs to replace the traditional car air conditioning heater core with a PTC wind heater, plus the corresponding auxiliary equipment. Ready to use. If we replace the PTC electric heater with the metal electric heater in the car air-conditioning products, the original air flow field will inevitably be changed due to the change of the internal structure. 2　 Feasibility study of PTC electric heater in air-conditioning products (1) Heating power test analysis. In conventional car air conditioners, PTC electric heaters are generally installed under the air inlet heat exchanger, and some are even directly installed on the air conditioner base or directly wrapped inside the heat exchanger. No matter how to install it, it is necessary to ensure that its heat dissipation surface and the air inlet direction maintain a certain angle, that is to say, when the air inlet through the PTC electric heater reaches the maximum, it can allow the PTC electric heater to exert the maximum power and generate relative heat. The effect will be the best. For example: install a PTC electric heater in a certain type of car air conditioner. When the ambient temperature in the car air conditioner is guaranteed and the car air conditioner is in a non-heating state, after the test power in the passed state reaches the design power, when the ambient temperature in the air conditioner reaches 53 At ℃, the power will decrease, the test value basically increases by one degree on average, and the power will decrease. After that, the wind speed is modulated to a low speed, and after the test, this stage will be less than the assumed standard power, so the power will suffer a certain loss as the temperature changes. This is of great significance to the effect of automotive air-conditioning products, especially the ability to control temperature will be greatly improved. (2) The calorific value can be adjusted automatically. Through the overview of the PTC electric heater, we know that its heating value will change according to the ambient temperature, that is, when the ambient temperature rises, the heating power will decrease, and vice versa. This not only can effectively realize the automatic adjustment of the temperature in the car, but also can make the air outlet temperature moderate and stable, which is conducive to the realization of the constant temperature effect of automobile air-conditioning products and the precise control of the temperature. At the same time, the application of PTC electric heaters in automotive air-conditioning products can also effectively save energy, and automatically reduce power when the temperature is high, while metal electric heaters are fixed heat output, and its heat generation will not Changes with temperature changes, so it is prone to waste of resources or excessive heater temperature, and the output temperature fluctuations are also large, which is not conducive to the realization of the constant temperature in the car, and it is also difficult to achieve the accuracy of the car indoor temperature. Regulation. (3) Security analysis. When the PTC electric heater is running in an automobile air-conditioning product, after testing, when the wind speed is zero, the surface temperature of the heating element will become higher.At the same time, because PTC has the function of self-limiting temperature, the resistance will drop after the temperature rises, and the In the burning state, the surface temperature is not easy to reach the burning point of the surrounding flammable objects, so it is difficult to produce an open flame, which can effectively avoid the emergence of fire problems, and has high safety performance.