Due to the tight packaging in vehicle interiors, the available physical space for HVAC units and distribution systems is very limited. Designers of climate control systems are often required to work around the geometrical restrictions imposed by other vehicle interior components, often without up-front understanding of the impact of potential design changes on system performance.
In addition, complex physics such as flow turbulence, thermal mixing, and radiation play important roles in determining airflow distribution, fan power requirements, and air temperature stratification inside the vehicle cabin. However, visualization and measurement of such physical effects are difficult in real vehicle applications.
System optimization in a climatic wind tunnel or through road testing for widely varying ambient conditions requires significant time and effort, particularly when some of the testing must be conducted for transient conditions. The evaluation matrix tends to be large due to various operating modes (defrosting, ventilation, bi-level, and footwell) of an HVAC system.