Fan noise reduction of household refrigerator

The authors describe the method of reducing the fan noise, especially the impeller noise, of a household refrigerator. The fan in the refrigerator tested is a propeller fan, and the fan unit consists of an impeller, which has four blades, a rear board, which covers the evaporator, and a front board, which has a number of openings. The flow through the openings freezes food in the freezer. By measuring the internal flow with a laser Doppler velocimeter, it was made clear that the flow through the impeller was not symmetrical to the axis. The unsymmetrical flow seems to be caused by the restrictions of flow passages, and it might produce the impeller noise. The search for the sound source by the sound intensity method indicated that the noise was radiated through the openings of the front board. Guiders were installed on the rear board in the fan unit to guide the flow away from the openings. As a result, the impeller noise was reduced, whereas the flow was kept almost the same