In addition to increasing the temperature inside the car, warm air also has the function of defrosting the windshield. In fact, the forms of automobile warm air are water heating, gas heating and PTC warm air device control. At present, cars are mostly controlled by water heating and PTC heater.
The title on Empa website is too scientific: "Turning off the air conditioner helps to save fuel"
The results show that the higher the temperature and humidity, the higher the fuel consumption brought by automobile air conditioning; When the temperature reaches above 20 degrees Celsius, the increased fuel consumption is about 10% to 20%, depending on the temperature and humidity. If the temperature reaches an abnormal level of about 40 degrees Celsius and the humidity is abnormal, the fuel consumption will increase by about 30% at most.
The novelty of this test is that it tells us that the energy consumption of automobile air conditioning is not only related to the outside temperature, but also related to humidity. It is more expensive to use car air conditioning in sauna days than in dry and hot weather. In addition, this test also found a feature of automobile air conditioning system design. It does not mean that when the outside temperature is lower than the set temperature of the air conditioner, the air conditioner compressor will not work. Only when the outside temperature is lower than 5 degrees Celsius will the compressor stop for self-protection. The reason is that air conditioning is not only used to cool the car, but also plays an important role in dehumidifying and preventing the moisture in the air from condensing and fogging on the car glass, causing safety problems.
In fact, the heating methods used by cars with different power forms are different. Most cars use water heating, and some high-end cars use water heating plus PTC heater. As for new energy pure electric vehicles, only PTC heaters can be used. The structure of water heating warm air is also very simple, and the cooling liquid is used for heat exchange. In the original system, a warm air water valve, a warm air water tank (heat exchanger), a blower, a temperature sensor, an air duct and a control system are added.
This has to start with the air heating mode of the aircraft. In the civil aviation passenger plane we usually take, the source of warm air is engine bleed air. By mixing the hot air of the engine with the low-temperature air outside, the appropriate temperature in the cabin can be obtained.
The air conditioner compressor is directly driven by the engine.
When the temperature is not too high, there are two options to reduce the temperature inside the car: either open the window for ventilation or turn on the air conditioner.
There has always been a saying in rivers and lakes that when the speed is low, you should choose to open the window for ventilation, and when the speed reaches a certain level, for example, when the speed is more than 50 kilometers per hour, if you open the window, the air resistance encountered by the car will increase greatly. It is more expensive to open a window than to turn on the air conditioner at this time.
This speculation is not unreasonable. With the increase of vehicle speed, the air resistance will increase exponentially (air resistance is square with speed). At this time, a large part of the engine power output is used to overcome wind resistance; However, opening the window will change the drag coefficient of the car, and the airflow passing through the window will greatly increase the resistance encountered by the car when driving, resulting in a significant increase in fuel consumption.
In the water heating mode, the engine will generate a lot of heat after starting, and the cooling system is also needed to assist in heat dissipation, so the water heating air conditioner will not increase the extra fuel consumption when exchanging heat. To put it bluntly, the heat of the engine is used to heat the air in the form of heat conduction.
Ok, let's summarize the knowledge that has been carried forward: First, driving air conditioners will probably increase fuel consumption 10% to 20%; Second, no matter how fast you run, turning on the air conditioner costs more money than opening the window; Third, closing the window without turning on the air conditioner is the most fuel-efficient (nonsense). By the way, add another hint. If you use an automatic air conditioner, if you press the A/C button, the compressor will work even if the outside temperature is low. If you set the air conditioner to the defogging position, the compressor will work even if the air conditioner button is not pressed.
What's the use of knowing this knowledge? Because it costs a lot of oil to turn on the air conditioner, official website, a Canadian natural resources department, suggested not to turn on the air conditioner unless it is too hot. In urban areas, you can cool down by opening windows for ventilation. On the highway, you can close the window, turn on the air supply switch inside the car, and adjust it to "external circulation" to send the natural wind outside the car into the car. If the air conditioner is turned on, the air supply in the car should be adjusted to "internal circulation" to improve the cooling efficiency.
Although it costs oil, the air conditioner still needs to be turned on. My suggestion is that you must open the door to ventilate before getting on the bus in hot weather. There are two purposes, one is to dissipate heat, and the other is to disperse "poisonous gas". Now you know the air quality control level of domestic cars. In hot weather, all kinds of aldehydes, benzene and benzene in automobile interior materials are released at an accelerated rate, and all of them will be absorbed into your stomach without ventilation. If you are in a hurry, open the window for a while after you start, then close the window. When ventilating, you can turn on the air conditioner first to dispel the dirty air in the air-conditioning duct.
When driving in urban traffic jams, you must start the "internal circulation", because the "toxic gas" in the car has dispersed, and it takes time to release it to a certain concentration. The automobile exhaust on the road has assembled, so it is best to keep them out of the car.
If you run a long distance and turn on the air conditioner for a long time, you still have to open the window for ventilation, or switch to the external circulation mode to let fresh air in, which is always "internal circulation" and the air inside the car will get worse.
In addition, the air conditioning filter in the car should also be replaced, preferably once a year. Winter smog, spring dust, four seasons exhaust, filter can be used for a year is good. It can help to purify the air (I personally measured that the filtering effect of some models of air conditioning filter elements is also obvious). If the filter element is too dirty, the air quality inside the car will deteriorate, and the filter element itself will also emit odor-it is sour, refreshing and enough for people.