Aerocoustic Noise Prediction of Passenger Car HVAC by using CFD and Validation with Test Result

The advancement of automobile industries demand compact size of HVAC with better cabin comfort. To achieve this, HVAC has to be optimized in all the aspects such as in shape & size, thermal comfort as well as in noise comfort. From an HVAC perspective, aeroacoustics noise is more significant due to its intensity at higher speeds and frequencies. Since HVAC is mounted inside the cabin, noise can transfer directly inside cabin. To avoid this, noise reduction or noise controlling is of very important. This is possible with HVAC design and simulation at the initial level and acoustic prediction after the CFD/CAA analysis. The present paper describes the aeroacoustic simulation of one of the HVAC to predict the noise during face mode. For that, 1-D simulation has been done initially to find the porosity of heat exchangers and coupled with a CFD solver. STAR CCM+ software is used for the CFD analysis. Transient simulation is performed with compressible fluid using a moving mesh approach. To perform the aeroacoustic simulation, the result from the CFD analysis is used by the acoustic software (Actran VI) which predicts the major noise source due to the flow path like re-circulation air opening, blower motor and downstream side of the HVAC. Physical model of HVAC is tested in a semi-anechoic chamber with standard ambient conditions. The test results of the HVAC is compared with the simulation results and good correlation observed between the simulation results and the test results.