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With the advent of quieter powertrain and improved cabin acoustic sealing, there is an increased focus on noise generated in the HVAC unit and climate control ducting system. With improved insulation from exterior noise sources such as wind & road noise, HVAC noise is more perceptible by the occupants and is a key quality indicator for new generation vehicles. This has increased the use of simulations tools to predict HVAC noise during the virtual development phase of new vehicle programs. With packaging space being premium under the instrument panel, changes to address noise issues are expensive and often impractical. The current methodology includes the best practices in simulation accumulated from prior aero acoustics validation studies on fans, ducts, flaps and plenum volume discharge. The paper details the acoustic noise generation and propagation in the near field downstream of an automotive HVAC unit in conjunction with ducting system.

This paper summarizes the numerical development of a cooling package in a vehicle. The radiator and condenser fan performance curves are predicted using Computational Fluid Dynamics (CFD) approach using a numerical AMCA (Air Motion Control Association) chamber. The same procedure is extended to generate the combined fan performance curves. System resistance curves at various vehicle speeds are determined. To determine the vehicle system resistance at various vehicle speeds, a full vehicle CFD model in a numerical wind tunnel is developed and analyzed at different fan speeds. The changes in radiator flow for different scenarios such as change in fan geometry and the removal of condenser fan are outlined in this work. The study is then extended to predict radiator hot flow and coolant inlet temperatures at different vehicle load conditions. An analytical method to determine hot air flow and air temperature at radiator exit is developed.

This paper discusses flow through the front end of a vehicle comprising all the underhood/underbody components. Two approaches used to model the fan to predict the front-end airflow in a full vehicle model using Computational Fluid Dynamics (CFD) are presented. The approaches discussed here are the Moving Reference Frame (MRF) model and the fan plane model. Both cold and hot flow conditions are carried out for the full vehicle model. This paper also outlines the determination of fan performance curves numerically. The data from the fan performance curves thus obtained can be used in a fan plane model. The paper also discusses two methods to determine the recirculation factor in front-end flow studies namely, the user-defined scalar (UDS) method and the heat balance method.

Advanced control techniques are widely used in different automotive applications including climate control. Significant costs associated with the development and calibration of such controllers can be reduced if these tasks are conducted in a virtual environment. Such a virtual environment can be developed by integrating the controller with the system model. Different scenarios can be then simulated to make sure functional objectives of the system are met. 1D models provide the necessary level of accuracy without imposing extra computational cost in such virtual environments. As such, they are perfect candidates for model, hardware or software-in-the loop validation benches for controls. Performance of a heating, ventilation and air-conditioning (HVAC) system can be controlled through the settings of the components like mode door, blend door, recirculation door, blower, and the compressor.

Active grille shutter (AGS) in a vehicle provides aerodynamic benefit at high vehicle speed by closing the front-end grille opening. At the same time this causes lesser air flow through the cooling module which includes the condenser. This results in higher refrigerant pressure at the compressor outlet. Higher head pressure causes the compressor to work more, thereby possibly negating the aerodynamic benefits towards vehicle power consumption. This paper uses a numerical method to quantify the compressor power consumed in different scenarios and assesses the impact of AGS closure on total vehicle energy consumption. The goal is to analyze the trade-off between the aerodynamic performance and the compressor power consumption at high vehicle speeds and mid-ambient conditions. These so called real world conditions represent highway driving at mid-ambient temperatures where the air-conditioning (AC) load is not heavy.