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This paper discusses the relationship between the Heating, Ventilation and Air-Conditioning (HVAC) subsystem (module) and vehicle noise levels from test results. Vehicle measurements were performed in semi-anechoic room with a binaural head at driver location. The reverberation room measurements on the subsystem level were performed on modules without ducts and at pre-selected inlet restriction. For a given vehicle segment as defined by the J.D. Power & Associates, the interior vehicle noise levels show a good correlation to the module noise over the entire flow rate range of the HVAC operation. The module and vehicle noise strongly depend on the vehicle segment. The results presented here can provide insight to the vehicle noise trends from module noise measurements and in writing vehicle and module noise level specifications.

Noise and vibration of passenger car thermal systems are some of the major contributing factors to customer satisfaction. The optimization of these characteristics requires an integrated approach involving detailed analysis, simulation and testing. This paper describes selected noise, vibration and harshness (NVH) issues, discusses solutions and provides examples of its successful applications for thermal systems in passenger cars. The major components of a thermal system include condenser, radiator and fan module, main HVAC module, auxiliary HVAC module as well as air conditioning (AC) additional components such as lines, seals, hoses and vibration isolators. All components can contribute individually or as a system to the noise problem. Significant sound level reductions and improvements in sound quality have been achieved applying detailed analysis, Computer Aided Engineering (CAE) tools, and advanced testing methods.

Cost saving and short turn-around time are two major challenges for the development of automotive HVAC modules and systems. Traditionally, the development process is test-driven with a typical workflow shown on the left-hand side of Figure 1: Utilizing experimentally validated Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) methodologies, engineers are able to predict the aerodynamic and thermal behavior of the HVAC module and ductwork as well as the structural design robustness prior to physical testing in the laboratory. In addition to providing comparable results to those achieved through testing (e.g. temperature regulation curves and airflow distribution) the CFD results provide unique insight into the complicated airflow and thermal mixing behavior inside the HVAC module and ductwork. The early integration of CFD into the design process allows many more design concepts to be evaluated than would be possible through testing alone.