The Secret of Heating: The Warm Hug of a Car

When it’s cold out, we take it for granted these days that pleasantly warm air is going to flow from the ventilation system’s vents. And yet the development and testing of heating is such a challenging discipline that sometimes the smile playing on your lips will literally freeze…

7. 1. 2020 Škoda World INNOVATION & TECHNOLOGY TECHNOLOGY

With this chamber, such tests can be conducted all year long. Gone are the days when we would have to wait for temperatures somewhere in the north of Europe, in a complex carefully shielded from the gaze of inquisitive cameras, to drop far below zero so that the heating could be given a proper testing. As of this year, ŠKODA has four environmental test chambers. What with the ever-increasing number of models, the development of the Indian car platform, and the completely new requirements of electric-car heating, they don’t get a moment’s peace.

When in use, the door has to be shut firmly and everything must be perfectly sealed. In the chamber, a car has been left to “freeze” for twelve hours at -20 °C and a specific amount of water, applied to the windscreen with nozzles, has transformed into a thick layer of ice. This simulates a frosty morning in extreme conditions. The heating system’s ability to heat the interior when the engine is idling is then tested to ensure that 80% of the windscreen is clear within 40 minutes, even at a temperature of -20 °C. At least, that’s what regulations demand.

However, ŠKODA has much more ambitious internal limits: all cars, regardless of the engine chosen, must defrost the windscreen much faster. “Everything is monitored with a special thermal imager. This gives us a precise picture of how everything works in the upcoming car, how the windscreen heats up and the ice melts,” says Jan Hrnčíř, air-conditioning development coordinator. The chamber is also an opportunity to test the air-conditioning’s performance, as the air can be heated up to +40 °C and powerful fluorescent lamps can recreate the same intensity of sunlight as in the desert. Here, too, designers can check how the ventilation system behaves during a drive: there are powerful fans in front of the car to replicate cold air flow.

However, it is only when prototypes reach a very advanced stage that they can be tested in the environmental chamber. “Chamber tests are the culmination of our efforts as they require a lot of preparation, time and money,” emphasises Jan Hrnčíř. “Testing takes at least two days because the prep work is complex and you need patience for a car to freeze completely. If we were to discover this late in the game that the proposed airflow falls short of our expectations, development would be protracted significantly. That’s where computer modelling comes in – it means that, come the test phase, we can significantly speed things up, so what would have lasted for months now takes a matter of days.”

Therefore, long before the first prototype sees the light of day, everything has been designed and tested at the internal aerodynamics department. “We start with a sketch or a model. Using this as a basis, we build a three-dimensional computational model for the computer simulation of airflow in the interior of the car that is under development. The outputs are pressure and velocity fields, i.e. we get a picture of where and how the air is acting and what the airflow velocity is,” says David Svítil, internal aerodynamics coordinator. “The computer simulation gives us a good idea of how the heating system will behave before we test it for real in the chamber,” says Jan Hrnčíř.

The chamber is used not only for defrosting, but also to conduct comfort testing in order to verify how quickly and efficiently the car can heat the interior. With petrol engines, the only source of heat is the engine. With diesel engines, there is also an additional heating element. Referred to as a PTC, it is actually a compact heater that, drawing on data from several sensors (outside temperature, coolant temperature, selected interior temperature and time since engine start), automatically heats the engine in three stages of 300 W. This has been made possible by the exceptional efficiency of current diesel units, which operate with a minimum of waste heat.

Not only is the car pleasantly temperature-controlled, a factor appreciated by anyone sensitive to the cold, seniors and even families with young kids, but there is also no longer any need to scrape ice from the windows. In addition, it helps to make the view out of the car better and safer. There is no significant increase in fuel consumption, as a half-hour of heating requires about 0.2 litres of fuel. That is set off by the fact that a similar amount of fuel is saved as a result of not having to heat up the engine. What’s more, an engine that has first been warmed up with independent heating releases fewer emissions than a cold powertrain when it is turned on. Anyone who has experienced the comfort of auxiliary heating will never want to give up this pleasant accessory.

Electric challenges

The new ŠKODAs built on the MQB37 platform, such as the latest ŠKODA SUPERB, offer unheralded possibilities for the heating system. In the most modern cars, the control unit receives information about the number of passenger based on the seat belts fastened, resulting in greater heating and cooling efficiency. This feature will be particularly important for electric cars and plug-in hybrids, where heating is one of the most energy-intensive appliances in the car.

Electric vehicles cars will benefit from a new heating system that uses a heating unit similar to that of cars with current diesel engines, only more powerful. Another upside of this is that there is no further heating medium, i.e. in cars with internal combustion engine cars, this is water. The electric convector heater directly heats the air coming out of the vents, with the added benefit of an unexpectedly fast supply of warm air.

So it is not true that electric vehicles are poor at heating. On the contrary, they are heated better and faster than internal combustion engine cars. However, the heat source does place significant demands on the on-board batteries, so the heat needs to be handled efficiently. As the recharging infrastructure grows and advances are made in overnight plug-in options, electric vehicles will let you pre-heat the interior or defrost the glass while they are still connected to the mains, without depleting the on-board batteries. Then, while you’re driving, you just need to top up the already comfortably heated interior every now and then.