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Thermal Load Reduction

The Fleet Test and Evaluation team partnered with Schneider National, Volvo, and International Truck and Engine to quantify thermal loads in trucks, identify areas for improved thermal management, and evaluate thermal management technologies.

Three photos of a Volvo long-haul truck. The photo in the middle is in the normal visible light spectrum. The other two photos have colors showing the infrared spectrum: the photo at left (uninsulated windows) is mostly blue and purple with yellow and red on and around the truck's windows; the photo at right (insulated windows) is almost entirely blue and purple (including on and around the truck's windows).

NREL quantified the heat transfer characteristics of a Volvo truck (middle). The infrared images show higher heat transfer from the truck with uninsulated windows (left) versus the truck with insulated windows (right).

The studies are part of the CoolCab project, a government-industry collaboration that focuses on the design and integration of advanced thermal management technologies in long-haul trucks. Work on the CoolCab project, which includes developing computer models of truck cab heat transfer and climate control and working with truck and idle reduction technology manufacturers to define idle reduction system requirements, is ongoing.

The results of the first study completed under the CoolCab project are featured in Thermal Load Reduction of Truck Tractor Sleeper Cabins.

Diagram of a long-haul truck with the names of thermal management technologies connected by arrows to various parts of the truck: Exhaust Heat Recovery (pointing to exhaust pipe), Advanced Seating - Low Mass (seating), Advanced Glazings or Shades (windshield), Efficient HVAC Equipment (engine compartment), Comfort-Based Air Distribution (driving cab), Infrared Reflective Materials (sleeper cab), Insulation (sleeper cab).

These advanced thermal management technologies being explored by the CoolCab project.

CoolSim HVAC Model

CoolSim provides a fully transient heating, ventilating and air conditioning (HVAC) model in the Matlab/Simulink environment for both integrated Autonomie and standalone simulation.

This NREL-developed HVAC system model uses a one-dimensional finite-volume formulation to solve energy, momentum, and continuity equations. Models of all the major components—compressor, condenser, expansion device, and evaporator—are included. Both mechanically and electrically driven compressor models are available to users. A mechanical model built in CoolSim was extensively validated to steady-state-component and system data. Results were within 2% of the test data.

Download

The CoolSim standalone typical light-duty vehicle mechanical A/C system and electrical A/C system models are now available for download, along with a short user's guide. Autonomie-integrated versions will be available soon, and heavy-duty models are currently in development. The models were tested with Matlab 2011b (7.13.0.564, Simulink 7.8) on Windows XP (32 bit) and Windows 7 (64 bit).

While NREL does not provide technical support for CoolSim, we welcome your feedback on the tool. Please email your feedback or report any problems to coolsim@nrel.gov.