Noise test and control for household refrigerator compressor
Sound comfort becomes more and more important in residential houses. Home appliance is one of the main sources of indoor noise. Noise emission is a distinctive feature for the selection of the home appliances. Noise levels in household appliances are increasingly attracting attention from manufacturers and customers. Refrigerators as common appliances used by most families run continuously all day. It produces a lot of noises. National standards have published severe rules on the acceptable noise levels, and noise-free operation becomes the preferred choice of customers in the refrigerators choosing. Therefore, it is necessary to reduce the noise level of refrigerator. In this paper, the noise control study has been carried on a type of air-cooled household refrigerator. The noise level of the refrigerator was tested under different operation conditions at first. Then the maximum sound pressure level and noise characters were obtained by analyse the spectra of the noises. Test data shown that the refrigerator noises are mainly composed of compressor and fan noises. According to the characteristics of the compressor and fan noise, a method of using sound insulation board was proposed to reduce the compressor noise. Considering the actual installation restrictions and the compressor cooling demand, a kind of sound insulation board with holes was applied. Experimental studies indicated that the proposed noise control method can suppress the noise of the household refrigerator effectively.
Source Identification and Noise Reduction of a Reciprocating Compressor; a Case History
A noise source can be very complex in nature. In noise control engineering an essential first step is to identify the strongest contributing noise sources. This paper discusses a practical case history, in which a series of measurement techniques was applied to a reciprocating compressor to identify the strongest sound source. In addition numerical prediction methods were used to give direction towards a lower noise design of the compressor. Structural modifications to the compressor are discussed, leading to a significant reduction of the noise levels. The sound power level of the reciprocating compressor was reduced by 5 dB. Moreover, from a perceptual point of view, customers experience the sound as more robust and more pleasant as well, probably because of shifting frequencies.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.