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An ultrasonic air temperature sensor, intended to help improve automatic climate control (ACC), has been demonstrated in a vehicle. Ideally, ACC should be based on inputs correlated with thermal comfort. Current ACC systems do not measure the air temperature best correlated to thermal comfort - at breath level in front of an occupant. This limits the thermal comfort that ACC can provide under transient conditions. An ultrasonic sensor measures the bulk air temperature, is transparent to the driver, and can use commercially available components. In a proof-of-concept test, we monitored the thermal transients in a vehicle during cool-down after a hot soak and also during warm-up after a cold soak. The ultrasonic path was along the roof console. The ultrasonic temperature always agreed to ±1 °C with the air temperature measured by a thermocouple at the midpoint of the ultrasonic path.

The focus of this study is to validate the predictive capability of a recently developed physiology based thermal comfort modeling tool in a realistic thermal environment of a vehicle passenger compartment. Human subject test data for thermal sensation and comfort was obtained in a climatic wind tunnel for a cross-over vehicle in a relatively warm thermal environment including solar load. A CFD/thermal model that simulates the vehicle operating conditions in the tunnel, is used to provide the necessary inputs required by the stand-alone thermal comfort tool. Comparison of the local and the overall thermal sensation and comfort levels between the human subject test and the tool's predictions shows a reasonably good agreement. The next step is to use this modeling technique in designing and developing energy-efficient HVAC systems without compromising thermal comfort of the vehicle occupants.

Simulation of cabin climatic conditions is becoming increasingly important as a complement to wind tunnel and field testing to help achieve improved thermal comfort while reducing vehicle development time and cost. Delphi developed the Virtual Thermal Comfort Engineering (VTCE) process to explore different climate control strategies as they relate to occupant thermal comfort in a quick and inexpensive manner. The comfort model has the ability to predict the local thermal comfort level of an occupant in a highly non-uniform thermal environment as a function of air temperature, surrounding surface temperatures, air velocity, humidity, direct solar flux, as well as the level of activity and clothing type of each individual.