extrinsic cycle
inner loop
How to use warm air to quickly raise the temperature inside the car in cold winter? I believe this problem has troubled many novice drivers, but the effective method of warming up is actually very simple. First of all, it is not how to control the switching of internal and external circulation, but how to improve the "hot car efficiency".
The heating system of fuel vehicle is quite special, which is completely different from the principle of household air conditioner using compressor and refrigerant for form conversion and using electric auxiliary heating module for heating. The warm air of an ordinary car is a "water heating system". Heating depends on the flow of engine antifreeze coolant. The warm air tank is heated by the high-temperature solution, and then the low-temperature air is blown through the high-temperature water tank by the blower, and the warm air is made according to the principle that the low-temperature object absorbs heat and raises temperature. Refer to the figure below for the principle.
Knowledge points: the basis of heating the warm air water tank is antifreeze coolant (referred to as coolant), but the coolant is not only low in temperature during cold start, but also does not flow to the water tank; Because in the heating stage of cold start, the control system adopts the flow mode of "small circulation" to quickly increase the temperature of the body and coolant.
That is, the cooling liquid only flows through the cylinder head to absorb heat and does not switch to the front cooling water tank to cool down; Until the temperature reaches about 90℃, the paraffin of the thermostat melts and expands, the small circulating water channel closes, and after the large circulating water channel is squeezed and opened, the overall temperature of the coolant will be improved. At the same time, adjust the air conditioning temperature to high temperature or screw it to the red line area. At this time, opening the windshield will open the valve of the warm air tank pipeline, and warm air will begin to appear. Therefore, how to speed up the temperature of the coolant is the core issue, otherwise there will be no warm air in any circulation.
Efficient hot car mode &; Technologies include:
1: The cylinder head and exhaust manifold are integrated, which is the mainstream rapid heat engine technology at present. The exhaust temperature of internal combustion engine is very high, and the temperature can still reach 900℃ after reaching the exhaust manifold. Then, by using this high-temperature airflow, the temperatures of the cylinder head and the coolant flowing through the cylinder head can be rapidly increased.
So novices can focus on this technology when choosing a car. Domestic cars such as Great Wall, Changan, Geely and BYD are used, and joint venture cars are also used by brands such as GM, BMW, Mercedes-Benz, Audi, Volkswagen and Fick.
2. Run normally immediately after starting, which is an effective way to get warm air quickly. The working basis of internal combustion engine is burning fuel, which will inevitably produce heat energy, which is the basis of raising the temperature of coolant; The idle speed of cold start is only about 1200 rpm, and the four-stroke engine does work once when the crankshaft rotates twice, that is, the idle speed is only about 600 times per minute.
However, the normal driving speed is 2000 ~ 3000 rpm. Taking an average of 2500 rpm as the standard, doing work 1250 times per minute will increase the speed of the hot car many times? Therefore, if you want to get warm air quickly, the best way is not to heat the car in situ; In-situ hot car is only an operation that has to be carried out in the carburetor era because the low-temperature fuel can not be atomized ideally. The EFI vehicles produced in the past 20 years do not need in-situ hot car, and lubrication is only formed in a few seconds. Don't listen to the so-called old driver's bluff.
Air conditioning cycle mode:
"Efficient heating and internal circulation" is the right choice! The so-called internal circulation means that the air conditioning system does not heat the outside air into the car, but forms an airflow in the car through the blower. Air enters the heater tank through the tuyere for heating, and then is sent into the car for heating.
Any low-temperature object will absorb the heat energy of high-temperature object or environment, but the air in the car does not rise much, so it flows out of the warm air tank once in a short time to heat up; Then only drivers and passengers, interior trim panels and windows are left to absorb air heat energy, and the speed of cooling will obviously be very slow.
But the external circulation is to pump out the low-temperature air outside the car and send it into the car after heating, and the heating result will be worse than that of the slightly higher temperature air inside the car; What is important is that most of the air in the car is still cold at this time. In this way, the hot air sent into the car will be cooled quickly, and the overall temperature will rise slowly, and the effect will inevitably be poor.
"Long-distance commuting, alternating internal and external circulation" is the safe way! Although internal circulation can make the temperature rise rapidly and maintain a fairly high standard; However, people's breathing in the car will quickly change the proportion of air in the car. For example, the proportion of carbon dioxide in normal air is only 0.03%, while the concentration of carbon dioxide in exhaled gas is as high as 4.2%!
Therefore, even if only 4% oxygen is actually consumed in each breath, carbon dioxide will increase rapidly by 1.40 times. In this way, the concentration of carbon dioxide in the air inside the car will increase to about 2.65,438+0.365,438+0% after a single breath for one hour (standard ≤B-class car or SUV). This will make the driver feel a little groggy, because the oxygen concentration of inhaled air decreases due to the increase of carbon dioxide, which means lack of oxygen.
Many automatic cars will not reach the level of fatigue driving when they drive hundreds of kilometers at a time, and fatigue is only due to lack of oxygen. The change of state after getting off the bus and breathing fresh air is enough to explain the problem.
If you commute with a full load, you will feel more tired. You know, although this gas is not toxic, it may be impossible to breathe if the concentration is too high. Therefore, it is suggested to switch the air conditioning system to external circulation every 1~2 hours for long-distance driving, so that the original air in the car can be squeezed out of the car together with the outside air, and the exchanged fresh air will make people feel refreshed. The topic of winter air conditioning is here for your reference.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.