The noise generation in domestic applications is currently a major factor for companies in the industry, along with energy consumption reduction and cost. Consumers usually associate high noise levels low quality products, and this brings the number of service calls and denigrates the image of the companies. For these reasons, the noise level has become one of the key factors for the domestic refrigerators project. One type of noise called expansion noise is generated by two-phase flow refrigerant at the evaporator inlet, and is the focus of this research line. The process in question produces a turbulent, compressible flow which can reach the speed of sound, generating a supersonic jet at the outlet of the capillary tube, which can cause an intense acoustic excitation.

In order to better understand the phenomenon, measurements are made with a typical frost-free refrigerator, equipped with a variable speed compressor, operating with R-600a fluid. In addition to the sound pressure measurements, accelerometers have also been used in order to try to correlate the acceleration signals with the sound pressure. A mathematical model for the prediction of thermo-acoustic performance capillary tubes will also be developed, in order to identify critical of vibro-acoustic point of view conditions and the influence of heat exchange with the suction line. Finally, they will be proposed practical solutions that can be implemented in refrigerators, which reduce the noise levels.