Space Technology Helps Delphi Take a Virtual Look at Thermal Comfort

FRANKFURT, Germany, Sept. 4 -- Engineers at Delphi Corp. have developed an innovative new computer-based modelling system that will help them enhance the "thermal comfort" of vehicle occupants. The new technique, called Virtual Thermal Comfort Engineering (VTCE), accurately predicts the temperature-related comfort level at critical areas on each occupant's body. As well as increased comfort for drivers and passengers, this allows climate control systems to work more efficiently and hence be smaller and require less energy.

"Traditional modelling techniques allow air flows and cabin temperatures to be analysed, but cannot show how changing factors such as air temperature and vent location actually affects the comfort of the occupants," explains Dr. Stefan Glober, director of engineering, Delphi Harrison Thermal Systems, Europe. "VTCE gives us this ability. It's a really exciting development that will lead not just to greatly improved comfort, but also to reduced system costs, better refinement, improved fuel consumption and lower emissions."

Before VTCE, the temperature of a person's breath served as the major indicator of thermal comfort. Although important, this approach left out critical parameters such as cabin humidity, outlet air velocity, solar radiation and the way air flows over each occupant. It also meant that the body was taken as homogeneous. "We've all been in cars where however fast the fans are running, some part of our body is still too hot," says Glober. "With VTCE we can look at the comfort of an individual's foot, a person's back where it rests on the seat, or any other area."

To achieve this, Delphi has developed new physiological modelling techniques using processes originally used by NASA to help increase the comfort of astronauts. The human body is divided into 16 relevant areas and the comfort of each area is calculated based on its thermal flow characteristics. A vast range of parameters can be assessed, including different body sizes, the effects of summer or winter clothing, different activity levels (concentrating on driving can increase body temperature) and how much a person is perspiring. The model also includes external inputs such as solar loading, humidity and ambient air temperature.

"Only around half of thermal comfort is achieved by having a powerful climate control system. Achieving the other half depends on clever management of air distribution and flows," says Glober. "VTCE gives us the ability to solve problems on existing vehicles or to provide a noticeably superior level of comfort in a new vehicle design."

VTCE also brings substantial benefits for the vehicle manufacturers, who could potentially reduce the capacity of air conditioning systems by up to 30% while still increasing comfort. It also reduces the time needed to develop climate control systems and greatly reduces the need for costly prototypes. In Europe, where VTCE has been installed at Delphi's Luxembourg Technical Centre, the system is already being used to help vehicle manufacturers meet tough ACEA (European Automobile Manufacturers Association) fuel consumption targets. Delphi supplies climate control systems for cars, commercial vehicles and, through its Diavia subsidiary, low volume niche vehicles. It was the first company to enter production with a system that senses occupant temperature, was one of the first companies to introduce a fuel-efficient variable compressor and is at the forefront of system integration and modularisation.