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This paper describes the development of an analytical tool for the design automation of the temperature blend door mechanism in an automotive HVAC system. The function of the blend door is to control the temperature of the air blown into the cabin interior by regulating the mix of air passing through the heater core. The objective in the design process is to achieve a prescribed function of temperature with respect to control position at the instrument panel. The control effort to effect the desired temperature change is also another important consideration for customer satisfaction. The current design process is empirical in nature and relies on laboratory and vehicle testing with prototypes. The process is also iterative in nature and may continue until the end of the overall design cycle of the complete air handling subsystem. A parametric feature-based computer model, described subsequently in detail, allows for virtual prototyping of the blend door control mechanism.

This paper describes computer software developed specifically for the analysis of airflow in the design of automotive A/C systems and its applications for improving performance of such systems. Traditionally, design of an A/C system involves building and testing of prototypes. The objective of this project was to develop predictive capabilities where an engineer can assemble a system in the computer to obtain desired air-flow performance. The computer program is integrated and customized for designing A/C systems. It has two parts: the first part, performance analysis, requires the air circuit modeling of an A/C system where each component is modeled in terms of appropriate design parameters. A system analysis is performed to predict the interaction of the components and the total system performance. The second part of the computer program performs component analysis.