F2010C203
Improving Passenger Compartment Thermal Comfort by Measuring and Controlling Equivalent Temperature
Determining "equivalent temperature" is an accepted means for assessing the thermal conditions inside of a vehicle passenger compartment. The equivalent temperature is defined as the "temperature of a homogenous space, with [zero solar load], mean radiant temperature equal to air temperature and zero air velocity in which a person exchanges the same heat loss by convection and radiation as in the actual conditions under assessment."
Passenger thermal comfort can be improved by adjusting the vehicle compartment air temperature to compensate for the asymmetric heating or cooling that is present in a natural environment. In other words, a vehicle compartment HVAC control strategy that is based on controlling air temperature to a constant value will not result in optimal passenger comfort without the manual manipulation of the air set-point temperature. Similarly, a control strategy that is based on the measurement of air and surface temperatures will not be optimal in the presence of solar loading that is directly experienced by the passenger.
This paper describes methodology for estimating real-time, in situ passenger compartment equivalent temperature for use in a thermal control strategy. A method to extend the calculation of equivalent temperature to include solar loading is presented. The advantage of controlling a passenger compartment thermal environment based on equivalent temperature is demonstrated by comparing thermal comfort as predicted by a virtual thermal manikin for both air-temperature and equivalent-temperature control strategies. The performance of the two thermal control strategies is first evaluated under steady state conditions that most passengers would find comfortable. Asymmetric, dynamic environments that represent typical vehicle compartment environments that would cause a passenger to experience mild discomfort are subsequently examined. The modeling and placement of sensors to measure air temperature, air velocity, surface temperature and solar irradiance in order estimate equivalent temperature is presented. Finally, the use of a virtual, real-time thermal manikin to optimize the thermal comfort is considered.
This abstract is supplemented by a PDF, which can be viewed here.