Airflow Management
Airflow in modern vehicles is carefully managed to ensure a comfortable cabin environment. Fresh air enters through a large duct located at the front of the car, strategically placed in a high-pressure zone so that as the car moves, air is naturally forced inside. This air can be directed to the heater, where it’s warmed if needed. Additionally, air can also enter through grilles positioned on top of the hood.
Air Distribution Inside the Cabin
The fresh air is then distributed into the cabin through vents located in the front footwells and on the dashboard. These vents can be adjusted to direct airflow towards the faces of front-seat passengers. Some vehicles also feature ducts that channel air to the rear-seat area for added comfort.
Window Defogging
To prevent windows from fogging, slots at the base of the windshield—and in newer models, near the front side windows—allow warm air to be blown onto the glass. Newer cars are equipped with flaps at all air entry points, which can be opened or closed as needed.
Air Extraction
At the back of the vehicle, exit vents are positioned in low-pressure areas. These vents help extract air from the cabin, ensuring a constant flow of fresh air throughout the car.
Heating System in Water-Cooled Cars
For heating, water-cooled cars utilize a heater unit containing a matrix, or small radiator, which receives hot water from the engine. The incoming air passes through this water-heated matrix, warming the cabin. An electric fan can be activated to push air through the system when the vehicle is stationary or when additional ventilation is required. The fan speed can be adjusted according to the driver’s preference.
Temperature Control: Water Valve vs. Air-Blending System
The air temperature inside the car is regulated by either a water valve or an air-blending system. In older vehicles, the water valve type is more common. The dashboard temperature control operates a valve that adjusts the amount of hot water flowing through the matrix, though this system can be slow to respond and difficult to fine-tune.
In contrast, the air-blending system keeps the matrix constantly heated. The temperature control adjusts flaps that mix warm air from the matrix with cooler outside air. Both systems may feature additional flaps to allow a separate stream of cool air to reach the face vents, even when the rest of the cabin is being heated.
Control Mechanisms
The flaps inside the heater box can be moved mechanically via sliding knobs on the control panel, connected by cables. In more advanced vehicles, these controls might be power-assisted, utilizing the engine’s vacuum to operate a diaphragm, similar to the power brake system.
Heating in Air-Cooled Cars
For vehicles with air-cooled engines, the interior heating is managed by directing air around the hot exhaust manifold’s fins. This warmed air is then mixed to the desired temperature using an air-blending system, which includes a heat-sensitive valve to maintain a steady and comfortable temperature for passengers. If needed, the air can be further heated using an electrically ignited, petrol-burning heat exchanger.
Car Heat Control
In a heating system that uses a water valve, the entire airflow passes through a heat exchanger, often referred to as a matrix. The temperature of the matrix is adjusted by controlling the flow of hot water through it. By varying the amount of hot water, the matrix’s temperature is increased or decreased, which in turn heats the air passing through it.
On the other hand, in an air-blending heater, the matrix maintains a constant temperature. Instead of adjusting the water flow, this system regulates the temperature by mixing warm air from the matrix with cooler air. Temperature-controlled flaps open and close to mix the air streams, achieving the desired temperature.
