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NREL - National Renewable Energy Laboratory
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Integrated Modeling

NREL's Vehicle Ancillary Loads Reduction (VALR) team predicts the impact of advanced vehicle cooling technologies before testing by using an integrated modeling process. Evaluating the heat load on a vehicle under real world conditions is a difficult task. An accepted method to evaluate passenger compartment airflow and heat transfer is computational fluid dynamics. (CFD). Combining analytical models with CFD provides a powerful tool to assist industry both on current vehicles and on future design studies.

Flow chart showing the vehicle integrated modeling process which considers solar radiation, air conditioning, and vehicles with CAD, glazing, cabin thermal/fluid, and thermal comfort modeling tools.  Results are provided for fuel economy, tailpipe emissions and occupant thermal comfort.

The vehicle integrated modeling process

The vehicle integrated modeling process includes:

  • CAD Model

    Defining the vehicle interior geometry using CAD data, if available, and generating a mesh for computational fluid dynamics (CFD) analysis.

  • Glazing Model

    Using Vehicle Solar Load Estimator (VSOLE) software to calculate the solar load on a vehicle passenger compartment based on vehicle geometry, vehicle orientation, solar radiation source, and window glazing properties.

  • Solar Radiation Model

    Providing solar radiation source data for VSOLE to calculate solar spectral irradiance incident on the vehicle as a function of location.

  • Cabin Thermal/Fluid Model

    Determining the flow field inside the passenger compartment, as well as the surface temperature, air temperature, and humidity.

  • Human Thermal Comfort Model

    Predicting the physiological and psychological response of a human to a transient, non-uniform thermal environment. See thermal comfort model for more information.

  • Transient A/C Model

    Estimating the possible air conditioning compressor power reductions from cabin temperature reductions.


    Using ADVISOR software to quantify the interaction between various vehicle systems, and their impact on fuel consumption and emissions.

For more information, read Integrated Numerical Modeling for Evaluating Automobile Climate Control Systems.

Learn more about the VALR team's other research and development areas.