AC Pipe Structural Dynamic Characterization in On–Off Vehicle Conditions

Abstract

AbstractThe dynamic behavior of heating, ventilation, and air-conditioning (HVAC) components can influence the vibration and noise been generated in the vehicle. Air conditional (AC) pipe is one of the most critical components in the vehicle HVAC system as it used to transfer different vapor and liquid conditions (high or low pressure) from the compressor to the evaporator. It is important to characterize the dynamic behavior of AC pipe in terms of natural frequencies, mode shapes, and frequency response function (FRF) to investigate the root cause of vibration and noise that been generated in the vehicle HVAC system such as hissing, humming, and clicking. This study will characterize the dynamic behavior of AC pipe in two different conditions, on and off-vehicle. Before installing the AC pipe to the vehicle HVAC system, its structural dynamic behavior will be investigated using an experimental modal analysis (EMA) in free-free condition (off-vehicle) to determine the dominant natural frequencies, mode shapes, and FRF. Then, after the installation, the EMA is conducted again as the mounted AC pipe to the vehicle engine bay structure (on-vehicle) may influence the original FRF. From the result, the first peak of AC pipe natural frequency has been shifted from 148 to 106 Hz with a decreased FRF amplitude due to effect of mounting in the vehicle engine bay. This result is important as it will contributed to the vibration and noise that been generated in the vehicle HVAC system during operation. Further, investigation on the different vibration and noise characteristics can be carried out to determine the root cause of the problems that been affected by the structural dynamic behavior of AC pipe.