Keeping your Passenger Comfortable in an Energy Efficient Cabin

Providing drivers and passengers with an adequate comfort level is a critical design objective. This is true across all modes of transport including: automobiles, trucks, off-road vehicles, trains and aircraft. HVAC climate control is a critical element in the highly influential and respected J.D. Power and Associates APEAL Study. Cabin cool-down and warm-up times are not only key design requirements but often regulated. Increasing globalization of brands means vehicles must be designed to operate in an ever wider range of environmental conditions with very high or very low ambient temperatures, strong solar radiation, and operate under sometimes extreme conditions with heavy loads on the engine. Vehicle electrification is adding additional efficiency requirements on the design of HVAC systems.


While it is obviously very important for cabin design to meet passenger comfort requirements, an active HVAC system can cut fuel economy by as much as ten percent, so efficiency of the entire climate control system is essential to good overall fuel economy.


Addressing cabin thermal performance early in the design cycle is critical to the key business objectives of occupant comfort and good fuel economy.



Cabin comfort assessment traditionally depends heavily on testing physical prototypes. Physical testing is very expensive, time consuming, and inflexible. Solar radiation is a critical component which can be reproduced only to a limited degree in climatic wind tunnels. Measuring surface and fluid temperatures is not sufficient Passenger comfort is a complex physiological function of temperature, heat transfer rates, air velocity, clothing, body type, body mass, and other factors. With physical testing such evaluations are very subjective.



Exa's solutions are ideally suited to address cabin comfort issues. PowerFLOW's unique, inherently transient Lattice Boltzmann-based physics allows simulations to be performed that accurately predict real-world transient conditions on the most complex geometry. The resolution of large scale turbulence allows for accurate prediction of the heat transfer coefficients. PowerTHERM is a fully-coupled, highly accurate, transient, conduction and radiation solver. PowerTHERM has sophisticated capabilities for modeling solar radiation and a best-in-class, proprietary, human comfort physiological model. The combination of PowerFLOW and PowerTHERM enables climate control engineers to accurately predict cabin air temperature over long time periods, calculate heat-up and cool-down times, and visualize the flow and temperature fields for the entire cabin. This enables the engineer not only to identify problem areas but to provide design recommendations that eliminate problems early in the design cycle. Rapid turnaround times for model setup, simulation, visualization and design modification allow the engineer to quickly make design changes to the baseline and evaluate the improvements in cabin comfort.


Benefits of using Exa's solution for cabin comfort analysis:


• Evaluate temperature distribution in cabin interior

• Evaluate passenger comfort level

• Optimize cabin HVAC flow

• Control cool-down/warm-up time

• Optimally size HVAC system capacity

• Predict system performance long before prototype builds







Selected References

Exa Product Overview


The Physics Behind PowerFLOW


Technical Publications Highlighting the Exa PowerFLOW Suite



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