Selection rules for automobile heaters
Based on experience, the selection rules for automobile heaters are summarized as follows.
1) The capacity of the car heater is not the bigger the better, but the heat dissipation of the engine under specific working conditions (generally at low temperature and low speed) must be considered. If the heat dissipation of the engine is small, the heat exchange capacity of the car heater is very high. If the car heater’s capacity is too low and the wind side heat exchange is insufficient, it will also affect the customer’s experience and cause complaints about insufficient heat. The water temperature cannot achieve the effect of higher wind temperature, and the two need to be balanced and matched;
2) The selection of the car heater is related to the setting of the thermostat opening temperature. The later the thermostat is opened, the better the heating performance, but the range of this selection will not be too large, because the engine is easy to turn on too late. Overheating, considering that the settings of general thermostats are between (80~90)℃, it is appropriate to take the inlet water temperature around 80℃ as the target value for design selection (usually the ambient temperature is 20℃, The speed of the vehicle maintains the speed of the general urban working condition, and different manufacturers and different sales regions have different requirements for this);
3) The pipe diameter of the automobile heater pipeline must ensure sufficient water flow of the automobile heater. The following is the range of common water flow. It should be specially pointed out that the current powertrain development and automobile heater development are usually relatively independent. Belonging to different suppliers, the pipe diameters connecting the two sections have been determined at the beginning of the system matching, so more pipeline optimization can only be the optimization of the pipeline direction to avoid excessive local resistance; in addition, the corrosion of parts The test shows that the water flow continuously exceeding 20L/min will cause certain corrosion to the core of the car heater, so the water flow is also limited; as the speed of the water pump increases, the coolant flow increases correspondingly, and the water side resistance increases accordingly. The three intersection points of indicates the matching point of the system under different pump speeds, and the arrow indicates the direction of change of the system matching point when the pump speed increases.