What is the difference between the internal circulation and external circulation in a car?
3 Answers
There are several differences between the internal circulation and external circulation in a car: 1. Different air circulation methods: Internal circulation allows the air inside the car to circulate in a closed state; external circulation brings outside air into the car. 2. Different air circulation states: Internal circulation involves heating or cooling the air inside the car before recirculating it back into the cabin; external circulation heats or cools the outside air before introducing it into the car. 3. Different working principles: The working principle of internal circulation is to promote air flow within the car. The working principle of external circulation is to use a fan to draw outside air into the car while expelling the interior air through another fan, achieving ventilation without opening the windows.
On my morning commute to work, I use this feature most often. Simply put, the fresh air mode draws in outside air, making the airflow from the vents feel fresher when using the AC in summer. But it has a downside – in traffic jams, using fresh air mode means all the exhaust fumes from nearby trucks enter the car. The recirculation mode is the opposite; it only circulates the air inside the car, making it ideal for tunnels or dusty weather, as it blocks most external dust and odors. However, experienced drivers advise against keeping recirculation on for too long, as oxygen levels inside the car can drop, leading to drowsiness. On highways, it’s best to switch to fresh air mode for ventilation every two hours. Remember to switch modes based on weather: when the windshield fogs up on rainy days, turning on fresh air mode with the AC defogger works wonders.
Since having a baby at home, I've become particularly concerned about the air quality inside the car during drives. In practical operation, simply press the button on the center console with the car logo and arrow. The external air circulation is equivalent to opening the windows for ventilation, but much quieter than opening windows and avoids drafts. Its air intake is usually designed at the junction of the hood and the windshield, so switching to external circulation immediately after turning on the heater in winter speeds up warming significantly. The internal circulation button features an arrow inside the car icon; pressing it keeps even the smell from roadside barbecue stalls from entering the car. Tests have shown that turning on the air conditioning with internal circulation activated at least doubles the cooling speed. However, be mindful that if the car air freshener has a strong scent, the smell can become overwhelming with internal circulation on, so remember to switch modes promptly in such cases.
