What are the Internal and External Circulation in a Car?

[Clark]

Internal circulation in a car refers to the process where the air inside the vehicle is heated or cooled and then recirculated back into the cabin. External circulation, on the other hand, involves drawing in outside air, heating or cooling it, and then introducing it into the cabin, facilitating gas exchange between the interior and exterior of the vehicle. Uses of internal and external circulation: 1. In cold weather, after starting the car and waiting for the engine temperature to reach normal levels, activating internal circulation can quickly raise the cabin temperature; 2. During high-speed driving, external circulation can be turned on as needed to maintain cabin temperature while ensuring fresh air supply. Advantages and disadvantages of internal and external circulation: The advantage of internal circulation is the rapid cooling or heating effect of the air conditioning system, while the drawback is that prolonged use may lead to poor air quality inside the cabin. The advantage of external circulation is maintaining clean air inside the cabin, but the downside is slightly less effective cooling or heating due to the influx of outside cold or hot air.

[ChristopherDella]

In our daily driving, the use of air recirculation (inner loop) and fresh air mode (outer loop) is actually simple yet crucial. The inner loop recirculates the air inside the car, with the AC only processing interior air. It's ideal for quickly adjusting temperatures in extreme weather or when outside air is polluted, such as during traffic jams or in contaminated areas, as it maintains cabin temperature more efficiently. The outer loop opens the exterior air intake, bringing in fresh air, which is suitable for long highway drives or poorly ventilated environments, preventing stuffiness in the cabin. Over years of driving, I often use inner loop with heating in winter to save fuel, and switch to outer loop on summer highways to prevent drowsiness. However, it's important to note that prolonged use of inner loop can make cabin air stale and oxygen-deficient, so remember to periodically switch to outer loop for fresh air—it's safer and healthier. I've seen people cough from inhaling exhaust in traffic jams because they didn't use inner loop—this small technique can significantly improve driving comfort.

[LeLincoln]

Briefly explain the car's air conditioning system: The recirculation mode closes the air intake, circulating only the air inside the car, equivalent to the car being in 'internal circulation mode'; the fresh air mode opens the air intake, allowing external fresh air to enter the cabin. From a technical perspective, there is usually a button symbol on the air conditioning control panel for this, and some cars even have automatic sensors to help switch between modes. In practical operation, I recommend using them flexibly based on weather and road conditions—using recirculation mode more often in summer for cooling can achieve faster temperature reduction and save energy; when encountering rainy days or fog, turning on fresh air mode is more reliable for preventing windshield fogging. As someone with some mechanical knowledge, I've observed that prolonged use of recirculation mode alone can lead to stale air, affecting driving concentration; while fresh air mode may not filter adequately if the external air quality is poor, requiring combined checks with the car's air filter. Ensuring a comfortable cabin environment is key—don't let simple functions go to waste.

[SanElla]

The use of internal and external air circulation while driving directly impacts safety and health. Internal circulation locks in the cabin air, ideal for avoiding external pollutants like dust or exhaust fumes, especially during highway traffic jams or in heavily polluted areas. However, the risk is that prolonged use can lead to carbon dioxide buildup, causing driver dizziness or fatigue, which increases accident risks. External circulation introduces fresh air, suitable for ventilation or long trips, maintaining oxygen levels and reducing motion sickness risks. The downside is that it may bring in dust in dusty areas. As someone who prioritizes family safety, especially when traveling with children, I recommend balancing usage—use internal circulation in tunnels or crowded areas to prevent inhaling exhaust, and opt for external circulation at other times for fresh air. Regularly checking the cabin air filter is also crucial to avoid bacterial growth affecting health. Simple choices can prevent unnecessary hazards.