HVAC in vehicles: the cold stays out

21-11-2018 | Posted by Principia

Recently it has become customary to watch TV series in paying platforms. Most people are familiar with them. And in some you really have a hard time. For example, watching Fargo, which takes place in Minnesota and normally in winter, in freezing cold. Mist clouds come out as people breath and cars have frost, if not ice, in practically all scenes.

You will note that vehicle manufacturers must struggle to get the HVAC systems to work properly, independently of the climate conditions and the patterns of use, a function of the time of the year and the geographical location, particularly if driving safety conditions are affected.

The design engineers must therefore provide HVAC systems that operate successfully in conditions of extreme cold, such as those in Minnesota. With outside temperatures of -20ºC, driving along the highway, the moisture caused by the breathing of the passengers can mist the windscreen and windows, which reduces visibility and could cause an accident.

HVAC systems must be designed to remove the film of mist formed and to prevent it from forming again. Obviously, the solution to this problem does not involve physical testing of different HVAC systems in Minnesota to find the right one, nor generating prototypes to test them in an environmentally-controlled wind tunnel; those solutions are too protracted, complex and costly.

It is much simpler to simulate the various climatic conditions and, through a digital twin of the HVAC system, evaluate the main design aspects, such as the speed and direction of the hot air flow, the compressor efficiency, the behaviour of the pre-heater and heater, or the ventilation characteristics of the car interior. And this analysis can be iterated as many times as needed before building a first viable prototype.

For the design engineers, the possibility of simulating digitally all these factors is of great help in detecting potential design problems that could lead to an inefficient performance, allowing even to witness the removal of mist from the windshield or the windows as a function of the options selected.

Numerical simulation is always a faster, simpler and cheaper solution than traditional prototypes in the early phases of design.

And now, yes, we can go to Fargo (Minnesota) in the middle of winter, knowing that we will have to fight with a bitter cold, but at least the windscreen will be free of mist.