Biphasic Flow, Noise, Refrigeration
Nowadays, the sound level and the sound quality are two very important buying criteria for the final users of a household or light commercial appliance. In order to assure good noise levels, the choice of a compressor with low noise at a specific condition is not the only point necessary to care. It is important to evaluate the transient noise, specially the one that depends on the state and the phases of the refrigerant. The goal of this paper is to present two studies, the first one showing how a biphasic flow in the suction line, close to the compressor in a drinking fountain can create transient noise due to the excitation of compressor gas cavity. The second case concerns the flow noise generated by the refrigerant in the capillary tube. In both cases, thermocouples are placed in different parts of the unit in order to better understand the behavior of the refrigerant flow. Different refrigerant charges are tested, verifying the thermodynamic and acoustic behavior of the units. Some different control techniques are also tried, aiming to avoid undesired noise (for example, pure tone) and reducing the overall levels. Finally, a proposed refrigerant charge is set, assuring a good trade-off regarding noise and thermodynamic performance.