Ensuring the air inside your car is just right - Škoda Storyboard

We take it for granted that the air inside cars can be heated or cooled to the desired temperature. In fact, this is far from simple. What’s more, the controls have to be used correctly. Here’s some advice from Škoda’s experts who design air conditioning systems.

Interior ventilation, heating and cooling may at first glance seem like a minor issue, but it affects the comfort and safety of modern cars. It takes the coordinated efforts of lots of engineers to ensure that a car can properly maintain the desired interior temperature and to prevent the windows from frosting over or fogging up. At the end of the day, though, the car’s users have to do their bit as well.

Modern air-conditioning vents are also a decorative feature on dashboards today.

“Internal aerodynamics refers to the airflow in the cabin. For us, this basically means that we design the ducts for the intake of fresh air, for its distribution around the interior from the air handling unit to the air vents, which are the ventilation system outlets into the interior,” explains David Svítil from the aerodynamics and CFD simulation department.

David Svítilaerodynamics and CFD simulation department

The vast majority of the work of the department’s engineers is done using virtual tools, so most components are developed using simulations. The prototypes are then only used to verify that everything works as it should. That entails making sure that the exhausts do not make unwanted noise, because the air velocity at the exhaust outlet can exceed 36 kilometres per hour and this can create a “whistle” effect. Having said that, normal air velocities are much lower, ranging from seven to 14 kilometres per hour.

Blowers for the rear seats on the Škoda Superb’s centre console

The central air handling unit is the basis of the heating, ventilation and air conditioning (HVAC) system. The unit contains heating and air conditioning modules. Škoda Technical Development engineers work with their colleagues in design to come up with a solution that not only looks good, but provides thermal comfort in the car’s interior and other necessary functions.

One of the most complicated parts of the HVAC system is actually the only one the car’s occupants can see: the ventilation outlets, i.e. the blowers. These are typically on the sides of the dashboard, in the centre of the dashboard and sometimes at the back of the centre console (for the rear seats). Less visible are the grilles at the bottom of the windscreen on the dashboard and, of course, the outlets under the dashboard or front seats where air is channelled towards the feet of front or rear passengers. Each of these elements has its own purpose.

The fourth-generation Fabia has playful circular vents on the sides.

The most complex are the dashboard blowers, which the driver and passenger can adjust with a joystick to direct the airflow over a fairly wide range – and it is here that the cooperation of the various departments is most needed. “Of course, the designers want the blowers to be as beautiful as possible, and we work with our colleagues in engineering to ensure that they also have the right function,” explains Svítil. It’s not just a question of the shape of these ventilation grilles, he says, but also their position in the interior.

Simulation of the flow of warm air on the Kodiaq’s windscreen

The vents are often a fairly distinctive feature of a car’s interior. The fourth-generation Fabia, for example, has playful circular vents on the sides; the second-generation Kodiaq SUV has elegant horizontally stretched grilles; and the fourth-generation Superb uses a hidden design that is one of the latest trends in this field. “The exhausts are concealed by the dashboard design with vertical ribbing and adjustable vanes. There are no horizontal slats – their function is handled by the two-channel internal structure of the blower,” Svítil says. The result is not only elegant, but also perfectly functional.

The latest-generation Superb has air-con outlets covered with a fine mesh and stretching the full width of the dashboard.

If the interior cooling or heating is to work as it should, the driver should know how some of its elements work. “Of course, everyone has different preferences for thermal comfort and climate. Some people like to direct the airflow towards themselves, while others prefer it to flow away from the body and with as little intensity as possible,” Svítil says. But he goes on to explain that there is a setting that is basically ideal in terms of the efficiency of the system.

Starting with the latest generation of the Škoda Kodiaq and Škoda Superb, the air conditioning can be set using digital Smart Dials. The driver and passenger use a pair of dials mounted on the sides of the dashboard to control it. The middle dial can then be customised to allow the driver to control up to four functions, choosing from infotainment volume control, fan speed, airflow direction, iClimate smart air conditioning, driving modes and map zoom. Between the rotary controls there are four additional hardware buttons that control windscreen defrosting, rear window heating, internal air circulation and automatic climate control.

That’s why today’s HVAC systems have a button for automatic adjustment. On automatic, the electronics, which are programmed by Škoda Technical Development, determine the parameters and the speed of air flow into the interior according to the current settings and the desired temperature. It’s so clever that it even takes into account the position of the sun, because the interior will naturally heat up more on the sun-facing side.

Octavia Airflow controls in the latest Octavia’s infotainment system.

The car’s occupants can help the system work properly. “Generally speaking, the best setting for the blowers is that the side ones point towards the side window and the ones in the centre of the dashboard point upwards. This ensures that the interior is heated or cooled from the window, which is the biggest source of cold or heat, and that air is delivered to the rear row of seats,” explains Svítil.

Simulation of optimal airflow in the Superb

This is also the quickest way to defog or defrost the car windows, which is an area covered by the homologation regulations carmakers have to comply with. “The homologation regulations are actually quite benevolent – our internal requirements are much stricter. We want to ensure the best possible thermal comfort for the occupants, and that goes hand in hand with ensuring the best possible view from the car,” says Svítil. That’s why, he adds, it doesn’t make sense to close the ventilation outlets, even though this is an option.

Setting up zonal air-conditioning in the Škoda Superb

The automatic setting also controls where the air should flow. In summer, when the interior needs to be cooled, it doesn’t let too much cool air reach the occupants’ feet, preferring to distribute it through the upper ducts. “Cool air descends and naturally cools the whole interior and the passengers’ bodies,” explains Svítil. In winter, though, it’s the other way around: the system sends warm air towards the feet and it naturally rises. Of course, the system has to make sure that the windows don’t fog up so some of the warm air has to be directed into the upper part of the interior.

Kodiaq Bird’s eye view of optimal airflow inside the Kodiaq

As far as fogging is concerned, it is also important to understand how the internal air circulation system works. Fogging isn’t a big problem in summer because the air conditioning also dehumidifies the air. At the same time, automatic control ensures that the air in the car is replaced with fresh air once in a while (there are standards governing the need for fresh air). In winter, though, even in modern cars, the circulation on can contribute to window fogging: heating alone cannot remove the moisture that accumulates in the interior, both from the occupants’ breath and from water or snow on shoes or clothes. This is why an intensive supply of fresh and constantly heated air is needed.