Why does the door glass fog when the weather is cold?

The principle of window fogging is "internal heat and external cold". The temperature difference between the inside and outside of the car 10-20 degrees Celsius, the carbon dioxide exhaled by the occupants in the car will condense into water vapor when it meets the cold glass and condense on the window. It is for this reason that water vapor is easily generated on the window glass at home in winter. This is an old problem, but it is not a small problem, because once the driving line of sight is blocked, within a few seconds.

There are two conditions for fogging, one is that the humidity is too high and the other is that the temperature is too low, and both are indispensable. Reason 1: Under the condition of constant air humidity, when the window temperature is lower than the dew point temperature, condensation will form on the window surface, which is the phenomenon of fogging on the front windshield that we often see. The second reason: there is a certain temperature difference on both sides of the window, and the temperature is low.

Fogging of glass is a physical phenomenon. After the window is closed, because the temperature inside the car is high and the temperature outside the car is particularly low, a large amount of water vapor in the car will liquefy into small water droplets when it meets cold glass, which is what we usually call fog, but the fog caused by the temperature difference between inside and outside affects safe driving. In this cold winter, I am really tired when I go to work as a driver.

When the vehicle encounters fog on the window glass, press the fan-shaped sign button, and the air conditioner will directly modulate the maximum air volume to blow the front windshield and front side window (some high-end models also have rear window air outlets), and it is best to use warm air in winter or cold weather; When the rear window is foggy, press the rectangular heating sign button, and the rear glass tungsten wire will be electrified and heated to remove fog and frost.

The air conditioner blows glass circularly outside, and both hot and cold air can be used.

The method to quickly remove the fog on the windshield of a car in winter morning or summer rainstorm is to blow with cold air, turn the air outlet switch to the windshield position, and turn the circulation switch to the outside of the car for circulation. Close the front air outlet, the air volume is slightly larger, and it can be cleared in about 2 seconds. There is also an AC switch, which can also demist after being pressed. Some people also call it a defogging switch, which has a slightly slower clearing speed.