Noise Control Technology for Freezers

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In the dead of night, the noise generated by the operation of the domestic refrigerator often appears particularly obvious. This continuous low-frequency sound may not only affect living comfort, but also have potential effects on physical and mental health after long-term exposure. Modern refrigeration technology has taken noise control as an important research and development direction. Through the integration of multidisciplinary technology, the noise level of domestic refrigerators has been reduced from more than 50 db in the early days to about 38 db today. In this paper, the generation mechanism and control methods of refrigerator noise are systematically analyzed from the perspective of technical principle.

1.Noise reduction technology of compressor

As the core component of refrigeration system, compressor is one of the main noise sources. The noise of compressor mainly comes from mechanical vibration, airflow pulsation and electromagnetic noise. Modern compressors adopt precision machining technology to ensure the matching accuracy of moving parts, and control the mechanical clearance at micron level, which greatly reduces the mechanical impact noise. In the aspect of airflow noise control, by optimizing the valve structure and airflow channel, the refrigerant flow is more stable. In the aspect of electromagnetic noise, sine wave drive technology and optimized stator winding design are adopted to effectively suppress electromagnetic vibration. The comprehensive application of these technologies, so that the sound power level of modern compressors than a decade ago reduced by nearly 40% .

2.Vibration control technology

Mechanical vibration will amplify the noise effect when transmitted through the structure. Modern refrigerators adopt multiple vibration reduction measures. The key of vibration control is to block the transfer path of vibration energy. The modern refrigerator adopts the principle of"Mass-spring-damper" system, and multi-stage damping devices are set between the compressor and the box. The hardness, thickness and shape of the rubber damping pad are carefully designed, so that it has the best vibration isolation effect in the working frequency range of the compressor. For the refrigeration pipeline, flexible connection and appropriate support spacing are used to avoid standing wave and resonance. In addition, the vibration radiation of the box wall can be effectively suppressed by pasting the constrained layer damping material inside the box. This technology can reduce the vibration and noise of the thin plate structure by 6-8 DB.

3.Control of airflow noise

Airflow noise control requires a combination of fluid mechanics and acoustics. The blade of the fan adopts airfoil design, and the tip clearance is controlled in a reasonable range to avoid vortex noise. The inner wall of the air duct adopts corrugated or porous structure, which destroys the coherence of sound waves. A guide vane is arranged at the sharp turning point of the air flow to make the air flow transit smoothly. The latest research shows that the bionic design of asymmetric blade structure, can further reduce the noise of specific frequency band. The experimental data show that the peak value of the noise spectrum can be reduced by more than 10 db under the same air volume.

4.Application of acoustic materials

The acoustic materials used in modern refrigerators often have multiple functions. For example, multi-layer composite sound insulation material is composed of high density layer, elastic layer and porous layer, which can control noise in different frequency bands. The microperforated panel sound absorption structure has excellent sound absorption performance at a specific frequency by precisely controlling the aperture and cavity depth. The new nanoporous materials have larger specific surface area and more complex pore structure, and the sound absorption coefficient can reach more than 0.9. The reasonable combination of these materials can make the refrigerator maintain good acoustic performance while lightening the weight.

Conclusion

Refrigerator noise control is a comprehensive technology involving mechanical engineering, acoustics, materials science and other disciplines. With the application of new materials and the development of intelligent control technology, modern household refrigerators have achieved significant noise reduction. In the future, with the progress of noise prediction technology and the improvement of active control methods, refrigerator noise control will develop in a more accurate and intelligent direction.