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.
Performance comparison with effect of door opening on variable and fixed frequency refrigerators/freezers
This paper presents the effect of door openings of refrigerators/freezers on the energy consumption and compartment temperature variation by experimental approach. Two types of refrigerators/freezers were tested in the study. One is a type of variable frequency operation, while the other is a type of fixed frequency operation. The testing procedure was conducted under the ambient temperatures of 15 and 30 °C, and the door opening operation was carried out by one automatic robotic apparatus in an environmental control room. From the test results, energy consumption of refrigerators/freezers with door opening was found to increase by 10%, compared to the same product without door opening. Based on the compartment temperature variation status during door opening, control strategy was also proposed to improve the efficiency of variable frequency type of refrigerators/freezers. Future study on door opening control methodology can be addressed on usage's characteristics, so that it would help to control temperature variation and improve energy utilization by minimizing the effect of door opening.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.