Experimental analysis of HVAC system level noise in mobile air conditioning (MAC) system

With the advent of new technologies and rigorous research and development in engines, cars are becoming quieter than ever. This has led to the noises which were earlier, masked behind engine noise being audible inside the passenger compartment. Having a quieter air-conditioning (AC) system would aid us in cutting down on this parasitic noise source. Making it one of the important parameters during the design and development of the Heating, Ventilation and Air-Conditioning (HVAC) system for a vehicle program. However, due to packaging constraints improper integration or selection of different AC parts, there is a possibility that the noise generated from the AC compressor to get amplified while the refrigerant flows through the thermal expansion valve (TXV) or through pipes. This is because the pressure pulsation, in the refrigerant flow, travels along the pipes and can amplify the noise if it is not properly dampen out. Also, TXVs can also be a source for noise if the quality of refrigerant - dryness fraction - is not optimized at the entry. The objective of the current work is to identify sources of noise, its propagation through pipes and some recommendations to minimize it. Current work also presents in detail the analysis of different parameters affecting refrigerant flow noise; like mass flow rate, refrigerant sub-cooling and super-heating, suction and discharge pressures and dryness fraction of refrigerant at system bench level. With above analysis new methods can be generated to identify and to subsequently minimize AC compressor noise.