non-condensable gases, expansion noise, energy consumption
The aim of this work was to experimentally investigate the effect of non-condensable gases on the thermal acoustic behavior of domestic refrigerators under dynamic conditions. To this end, an acrylic made filter dryer was installed in the system for a proper visualization of the refrigerant flow at the capillary inlet. An accelerometer was also installed at the evaporator inlet to capture vibrations/noise signals, caused by the refrigerant pattern at the inlet of the expansion device. During the experiments the energy consumption was measured with the system systematically doped with precise amounts of nitrogen. It has been found that the energy consumption increases by 13%, when a mass fraction of 0.43% of N2 is added to the system. Moreover, it has been found that the energy consumption increases almost linearly with the N2 mass fraction. Pull-down tests were also carried out, showing a clear relationship between the N2 amount and the power and mass flow rate oscillations, soon after the compressor start-up, caused by the unbalance between the compressor and capillary tube mass flow rates. It was also observed that the noise level is higher when liquid refrigerant enters the capillary, thus increasing the corresponding mass flow rate.