Two thirds of Mercedes SLK and Mercedes SL models are ordered with AIRSCARF®, making the neck-level heating system one of the most popular optional extras for these two model series. This patented system functions like an invisible scarf, which warms the occupants’ head and neck areas. AIRSCARF® is integrated into the backrests of the front seats and provides warm air through outlets in the head restraints. The Mercedes engineers have modified this unique innovation specifically for the E-Class Cabriolet: in this model, an adjustment wheel pivots the outlet nozzle upwards and downwards by a total of 36 degrees over and above the head restraint height adjustment, meaning that the driver and front passenger can enjoy the unique neck-level heating regardless of how short or tall they are.
In combination with the AIRCAP® automatic draught-stop (see page 23 of this press kit), the innovative neck-level heating system is even more effective at providing a flow of warm air, since the air inside the E-Class Cabriolet is already pre-heated before it is taken in by the blower in the backrest and passed through an electric heating element with an output of around 200 W and an operating current of 19 A. From here, the warm air passes through a plastic duct into the head restraint, where it is blown out of the adjustable air outlet. In this way, the Mercedes experts are able to provide warmth for all the occupants and pleasant temperatures at head height for the driver and front passenger when a cold wind is blowing over the Cabriolet.
As well as requiring very little space, this innovative Mercedes technology also has the major advantages of delivering warm air quickly and providing a constant heat output. The heating element in the backrest is based on sophisticated PTC (Positive Temperature Coefficient) technology: ceramic particles are energised so that they heat up in a matter of seconds and then give out continuous heat. The ceramic system protects itself against overheating by monitoring its own surface temperature and reducing the power consumption automatically when required. Nevertheless, the heating effect remains constant.
AIRSCARF® can be started at the push of a button. At speeds of up to 120 km/h, a control unit calculates the ideal warm air distribution automatically – depending on the interior and exterior temperature, on whether the soft top is open or closed, and on the vehicle speed. Above this speed, the system operates on a constant setting. Furthermore, the driver and front passenger can set the speed of the radial fan and, therefore, the heat supply, to any one of three levels, all at the push of a button on the centre console. The powerful AIRSCARF® system produces up to 27.4 kilograms of warm air per hour.
Shots taken using the thermography camera show how effectively the patented AIRSCARF® system operates at low outside temperatures in winter. Costing some € 50,000, the special camera enables people to see that which usually remains invisible: the heat radiated by persons or objects.
The principle at work here is as follows: at temperatures above absolute zero (i.e. minus 273 degrees Celsius), all objects essentially radiate heat – even ice cubes or snowballs. This thermal energy is infrared light with a wavelength that the human eye cannot perceive. The higher the temperature of the object, the more intense its infrared radiation.
The AIRSCARF® tests conducted by the Mercedes engineers using the thermo-graphy camera are based on this fundamental physical principle. The camera’s highly sensitive lens scans the driver, the seat backrest and parts of the interior, making heat visible: zones with high heat radiation appear in red, violet and white on the monitor, while cooler areas are coloured green or yellow. The dark blue and black areas, on the other hand, are the areas where the temperature is at its lowest. The thermograms clearly show where a large, wide sea of warm air is produced in the E-Class Cabriolet.
In addition, testers wear special measuring shirts during the tests. These garments are equipped with a total of 14 measuring points distributed around the throat, neck and shoulder areas, which can measure the various temperatures individually, allowing the distribution of warm air to be analysed.
When developing the AIRSCARF® components, the Mercedes engineers naturally placed great emphasis on occupant protection. This is why the outlet in the head restraint is slightly recessed and only clips into place. In the event of a crash, the outlet can disengage and move out of the way so as not to pose an injury risk for the occupants’ heads. Furthermore, the fact that the outlet is recessed prevents the head from coming into contact with the hard components when the occupant leans back against the head restraint as normal.