This article presents a multistage, coupled thermal management simulation
approach, informed by physical testing where available, to aid design decisions
for PACCAR’s SuperTruck II hybrid truck cabin concept. Focus areas include cabin
insulation, battery sizing, and sleeper curtain position, as well as heating,
ventilating, and air-conditioning (HVAC) component and accessory configurations,
to maintain or improve thermal comfort while saving energy. The authors analyzed
weather data and determined the national vehicle miles traveled weighted
temperature and solar conditions for long-haul trucks. Example weather day
profiles were selected to approximate the 5th and 95th percentile weighted
conditions. A daylong drive cycle was developed to impose appropriate external
wind conditions during rest and driving periods. Using the National Renewable
Energy Laboratory’s vehicle HVAC modeling and simulation tool VTCab, HVAC load
design trade-off studies for the new truck geometry concept were completed.
Parameters analyzed included effects of paint color, insulation, glass
transmissivity, and curtain location. Simulation results helped with early
design material selections for efficient cabin climate control. A detailed
three-dimensional computer-aided engineering (CAE), computational fluid dynamics
(CFD), radiation, and human physiology co-simulation, referred to in this
article as CAE Thermal-CFD, was used to evaluate thermal comfort and energy
impacts of diffuser configurations and air supply settings in driving and
hoteling modes. Analysis revealed that it is more difficult to heat the cabin in
hoteling mode during the winter than to cool the space in the summer. This
seasonal load profile drives the requirement of additional energy storage for
heating comfort. To determine the battery capacity requirement, multiday HVAC
operation drive cycle simulations were then completed, showing that a 15-kWh
battery would be required for HVAC operation during hoteling. Results helped
reduce cabin thermal loads, determine component sizing requirements, and improve
occupant comfort to save fuel and contribute to the economic viability of the
hybrid system.
