What is the Difference Between Internal and External Air Circulation for Heating?
3 Answers
The main differences between internal and external air circulation for heating are: 1. Different thermal insulation effects: In internal circulation mode, the airflow passage between the inside and outside of the vehicle is closed, and there is no airflow circulation without the fan running. In heating mode, this ensures the temperature inside the vehicle. External circulation mode uses the fan to draw outside air into the vehicle, meaning there is airflow between the outside and inside of the vehicle. In heating mode, the warm air inside the vehicle is more easily carried away. 2. Different fuel consumption: Using internal circulation in heating mode results in slower heat loss and lower fuel consumption. Using external circulation in heating mode leads to faster heat loss and higher fuel consumption.
Having driven for over twenty years, I've noticed significant differences between the air recirculation and fresh air modes in the heating system. The recirculation mode circulates only the air inside the car without drawing in cold outside air. It's particularly useful for quickly warming up the cabin when you first get in the car during winter, or when outdoor air pollution is high - you can feel warmth within three to five minutes. The fresh air mode, however, introduces outside air into the vehicle to maintain air freshness, especially important during highway driving to prevent CO₂ buildup and avoid dizziness. Its drawback in cold weather is that it may cause temperature drops, requiring the heating system to work longer to restore warmth. A common practice is to start with recirculation for quick warming, then switch to fresh air for ventilation. Remember not to use recirculation mode for too long, as it can increase humidity inside, leading to fogged windows that impair visibility - switch to fresh air or use the defroster function when needed for safety.
As a parent who frequently travels with kids, I understand the importance of interior and exterior air circulation for family comfort. Interior circulation recirculates cabin air, providing quick heating and better fuel efficiency, making it ideal for short trips or rapid warming—perfect for keeping kids warm during winter outings. However, prolonged use can lead to stale air, making children drowsy or prone to colds. Exterior circulation introduces fresh air, diluting cabin pollutants, especially when the car is crowded, preventing CO2 buildup and driver fatigue. Yet, in cold weather, exterior circulation may slow heating, so timing is key—switch after the cabin warms up or at red lights in open areas. On long trips, prioritize exterior circulation to ensure healthy breathing for everyone.
