Parametric optimization and analysis of metallic porous material used for discharge system of hermetic compressor

Gas pulsation is an important noise source in household refrigerators. The pulsation is generated in the compressor discharge chamber and it is transferred to the cabinet through the condenser, which is directly connected to the back of the system. The discharge muffler makes a considerable contribution to refrigerator noise. The noise can be controlled through the use of metallic porous material in the expansion chamber of the muffler. The macro-acoustic parameters of porous medium (airflow resistivity, porosity, tortuosity, viscous and thermal length) were characterized experimentally to validate numerical and analytical results. The porous material was modeled, using Johnson-Champoux-Allard (JCA) approach, as an equivalent fluid. Parametric optimization was employed to maximize the transmission loss of the dissipative muffler. The optimized frequency range was 500 Hz to 5 kHz. Prototypes were developed with different distributions of porous material in the chamber and they showed improved performance compared with the reactive muffler.