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Analysis of the root causes of refrigerant-induced noise in refrigerators
Abstract and Figures
Refrigerant-induced noises, which occur irregularly at special thermodynamic cycle conditions, are frequently cited by residential
customers who use refrigerators. However, these noises are very difficult to resolve and their root causes cannot usually
be exactly identified. In this research, the root causes of the irregular refrigerant-induced noise are estimated through
the theories of two-phase flow and bubble dynamics. Also, by using refrigerant-supplying equipment that can continuously supply
refrigerant to the test unit at typical cycle conditions, the flow patterns of the evaporator in vertical and horizontal pipes
are inspected and their noises are simultaneously measured. Through the observation of the relationship between the flow pattern
and the refrigerant-induced noise, the root causes of this irregular refrigerant noise can be identified and verified.
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... Half of these studies evaluated the noise within the flow, while the other half built anechoic chambers to measure the noise from outside. Unfortunately, as an attempt to investigate the crosscorrelation between the noise and the flow pattern, only part of the authors performed flow visualizations [3,6,35,[43][44][45][46][47]. Researchers also evaluated the structural excitation acceleration as an attempt to crosscorrelate it to the flow pattern [2,14,35,43,48]. ...
... Unfortunately, as an attempt to investigate the crosscorrelation between the noise and the flow pattern, only part of the authors performed flow visualizations [3,6,35,[43][44][45][46][47]. Researchers also evaluated the structural excitation acceleration as an attempt to crosscorrelate it to the flow pattern [2,14,35,43,48]. Flow patterns were characterized based on either visual observations or flow pattern prediction methods from literature. ...
... By considering that the noise from the compressor is sufficiently low, Han et al. [43] assumed that the SPL from 250 to 2000 Hz is due to refrigerant flow-induced noise. Corroborating these findings, Wang et al. [50] pointed out that the bubble bursting noise occurs mainly from 300 to 2500 Hz. ...
This paper presents a state-of-the-art review of the literature concerning flow-induced noise in expansion devices. The topics covered are theoretical natural frequency models of bubbles with spherical and cylindrical shapes and flow-induced noise in capillary tubes, such as orifice, thermal and electric expansion valve. Several parametric conditions affect the flow-induced noise in capillary tubes, such as outlet capillary geometry, capillary inner diameter and length, flow orientation, outlet vapor quality, mass velocity, pressure drop, in/outlet flow pattern, evaporation temperature, and refrigeration cycle operational conditions. Despite the broad use of orifice, there is a lack of knowledge in the literature of flow-induced noise in these devices. The flow-induced noise seems primarily a function of mass velocity, vapor quality, and flow pattern. It seems that outlet intermittent flow patterns lead to significant noise in capillary tubes and expansion valves. In general, for the noise evaluated outside the expansion device, electric expansion valves exhibited higher sound pressure levels than capillary tubes. Furthermore, the present literature review indicates that efforts should be made to perform tests for a wide range of conditions evaluating the noise within and outside the expansion device, device wall acceleration and flow topology for current and new refrigerants, simultaneously.
... Hirakuni [4] suggested that porous metal should be installed in front of the expansion equipment to change the flow mode from the slug flow to bubble flow, thus reducing the noise. Later, Han et al. [5,6] also analyzed the influence of the annular flow on the acoustic performance of the expansion valve and proposed to reduce the noise by controlling the flow rate and the dryness of the refrigerant. Enrique and George [7] studied the influence of system operation on the noise of expansion equipment through experiments. ...
... e flow in the bend also includes two aspects: the evaporation of the refrigerant and the secondary flow. As shown in Figure 10, from sections (4) to (5), the liquid core begins to contact the wall of the bent pipe. In section (4), there is still a clear liquid core. ...
A combined numerical-experiment investigation on the flow and acoustic field of an electronic expansion valve (EEV) is conducted in this paper. In an electronic expansion valve (EEV) under refrigeration condition, it is usually complex about internal flow. There are high pressure gradient and velocity gradient in the flow field, and it also involves the process of flashing phase change, physical property change, and heat transfer, which is difficult to simulate directly. After many explorations in this paper, the flow field of EEV under refrigeration condition is simulated by a four-step computational fluid dynamics (CFD). On this basis, the noise of EEV which is induced by the internal turbulent flow and propagates outward through the shell of EEV is simulated by a Hybrid Method. Numerical simulations of the mass flow rate (MFR) and sound pressure level (SPL) are verified by experimental data. Then, the characteristics of the internal flow field causing the external acoustic radiation are analyzed and used to create an improved design that can reduce the SPL while the MFR hardly changes.
... Refrigeration equipment operates in a cyclic mode, and the capillary outlet throttling noise determines the overall noise level, especially the cavitation noise, as described by [5,6], but it has not yet attracted attention [7]. Cavitation noise arises from the transition element between the capillary tube and the evaporator. ...
... is indicates that the pressure of the intermittent flow will fluctuate irregularly, and the pressure fluctuation will act on the pipe wall and then produce obvious vibration and noise. When the flow pattern is annular or bubbly flow, the dryness and cavitation fraction hardly change with time, so the time gradient of pressure drop is very small, and thus the resulting noise sound pressure level is small and basically constant, which is significantly lower than the vibration and noise level of slug flow [5]. ...
The aim of this work is the reduction of the throttling noise when the capillary is used as a throttling device. Based on the theory of bubble dynamics, two-phase flow, and aerated supercavitation, four different sizes of aerated devices used in refrigerator refrigeration systems are designed. Throttling noise and the temperature and pressure of inlet and outlet of the capillary are measured under stable operation. To compare the noise suppression effects in different groups of experiments, we introduced the cavitation number to analyze, revealed the principle of aerated supercavitation to suppress noise, and combined the results of Fluent simulations to get the relationship between the noise suppression effect and the aerated quality. The experimental results showed that the aerated device can obviously suppress the throttling noise of the capillary outlet, up to 2.63 dB(A), which provides a new way for reducing the capillary throttling noise.
... Han et al. [117] studied the noise from the refrigerant at the evaporator inlet and capillary tube outlet and found that due to the transition from expansion to evaporation, bubble formation and interaction caused some degree of flow-induced noise. Therefore, novel studies regarding the noise mitigation of refrigerators produced by compressors are vitally important in reducing energy consumption and increasing energy efficiency [118]. ...
This paper addresses the energy efficiency issue in household appliances, which has led to the establishment of policies at a global level in favor of setting minimum energy performance standards (MEPS), which guarantee end users are able to select more efficient equipment. The countries of the United States, Brazil, Mexico, Chile, and the Community of the European Union were taken as references to review their policies and implementation strategies, in order to be compared with the Colombian panorama (at the market, technical and political levels). This allows the establishment of common aspects and differences related to the determination of energy consumption, adjusted volume, and formalization of efficiency ranges, and in the specific case of domestic refrigeration. Managing to distinguish the most relevant aspects for the successful adoption of these policies in Colombia. It is evident that the implementation of these guidelines has a positive impact on the market of the countries and communities of reference. Similarly, the MEPS are shown as a mechanism to regulate energy consumption in the residential sector.
... Han et al. in their study dealt with noise originating from refrigerant at the evaporator inlet and the capillary pipe outlet in two different studies. The study showed that due to the transition from expansion to evaporation, bubble formation and interaction caused some degree of flowinduced noise [7] [8]. ...
Vibration and noise are undesirable effects in daily life and energy-consuming systems. In this study, the effects of different refrigerants on noise and vibration in a sealed reciprocating compressor are discussed. The study compared the noise and vibration performances of refrigerants with lower ozone depletion potential (ODP) values compared to R22, which has a high ODP value. The study was carried out experimentally in two stages. Firstly, tests were conducted for the coefficient of performance (COP) of different refrigerants. Secondly, vibration and noise data were obtained experimentally for different refrigerants. The results obtained from the experiments showed that both the COP value and the compressor vibration and noise have different values for R22 refrigerant and other alternative refrigerants, but values close to R22 are obtained. It was observed that the compressor noise values and vibration values vary depending on the type of used refrigerant. Average vibration values were determined as 0.604 m/s 2 in R22, 0.603 m/s 2 in R438A, 0.593 m/s 2 in R417A, 0.622 m/s 2 in R422D and 0.637 m/s 2 in R422A. When the noise values are examined, it was measured as 61.327 dB for R22, 62.913 dB for R438A, 62.187 dB for R417A, 63.715 dB for R422D and 64.913 dB for R422A. R417A, which has a 99% similar noise value to R22, was determined as an alternative refrigerant. COP values were found as 4.07 in R22, 3.98 in R438A, 3.63 in R417A, 3.37 in R422D, and 3.18 in R422A. R438A showing 95% similarity for COP can be used as an alternative to R22. Generally, it was observed that the noise and vibration values are very close to each other for all refrigerants examined. © 2021, Advanced Researches and Engineering Journal (IAREJ) and the Author(s).
... Min Seong Kim et al. proposed using the noise model diagram to predict the noise caused by refrigerants in refrigerators [10]. Hyung Suk Han et al. studied the refrigerant flow pattern and bubble characteristics at the inlet of the evaporator and discussed the relationship between refrigerant noise and bubble characteristics [11][12][13]. Yubo Xia et al. established a transition tube with different structures between the capillary and the evaporator and experimentally studied the influence of refrigerant flow state in the transition tube on the refrigerator noise [14]. When the refrigerant is in twophase flow state, it usually produces refrigerant flow noise. ...
The degree of bubble bursting at the inlet of an evaporator is the key factor to determine the size of the injection noise at the capillary outlet. In this study, by using the theory of cavitation dynamics, the transition tube between the capillary and evaporator is improved to suppress the bubble bursting at the entrance of the evaporator, so as to reduce the jet noise at the outlet of the capillary. The influence of aeration structure on noise reduction of a refrigerator (Haier BCD-520) was studied by numerical simulation, and experiments were carried out. The results show that the admixture structure significantly inhibits the bubble bursting and reduces the injection noise by 1.5 dB(A).
The refrigerant flowing through an electronic expansion valve (EEV) of a multi-split air conditioner is usually in two-phase state which may generate more severe flow noise than that in sub-cooled state. The purpose of this paper is to experimentally investigate the influences of the two-phase R410A operation conditions on the flow noise characteristics in the EEV, including listening sense forms, frequency distributions and sound pressure levels (SPLs). The experimental conditions cover the refrigerant mass flow rate ranging from 30 to 90 kg h–1 and the refrigerant quality ranging from 0.02 to 0.4. The results show that low mass flow rate facilitates the reduction of noise frequency, and the peak noise frequency was reduced by up to 32% as the mass flow rate decreased. Low refrigerant quality helps to reduce the SPL of flow noise, and the average SPL decreased by 6 dB as the refrigerant quality decreased. The guidance of inlet flow pattern by transforming the churn flow to the annular flow helps to simultaneously reduce the noise frequency and SPL, and the peak noise frequency as well as the averaged SPL decreased by 47% and 4 dB, respectively. Moreover, the hissing noise and the gurgling noise are the only two kinds of listening sense forms of flow noise detected in the present experiment, and the peak frequency and the average SPL of hissing noise are both higher than those of gurgling noise.
India as developing as country noticed growth in ceramic industries owing to development in construction sector, energy sector, space research, and health sector. Ceramic product is produced by technique of heat and ensuing cooling. It has numerous categories of products, including sanitary ware, refractory, cement, advanced ceramics, and ceramic tiles. Production process of ceramic product processing having three different stages: pre-kiln stage, kiln stage, and post-kiln stage. Pre-kiln stage rejections can be pushed back into the process, and it increases the cost of reusing as most of the time is required in the pre-kiln stage. Thus, pre-kiln stage rejection leads to decrease productivity and increases cost. This provides a base of research to reduce pre-kiln rejections with the help of root cause method in ceramic industry. Kaizens are introduced for reducing pre-kiln rejections and improving productivity. Root cause analysis (RCA) has been used for identification of various causes of pre-kiln stage rejection. By the use of RCA and some Kaizens 70% drop in pre-kiln stage refusal noticed leads to productivity enhancement.
Presently, from the viewpoint of comfort in air conditioning, noise reduction is being a matter of importance. This study focuses on the problem of noise in indoor air conditioners caused by the refrigerant flowing through the expansion valve. We investigated a method by which to reduce the low-frequency intermittent flow noise. It is supposed that this intermittent flow noise is related to the flow pattern of the refrigerant through the expansion valve. We carried out an experimental investigation to establish a correlation between flow pattern of refrigerant and consequent noise. It is shown that the noise is reduced if the flow of refrigerant at the inlet area of the expansion valve is made continuous both in gas and liquid phases.
Presently, in our quest to develop low-noise air conditioning equipment, it is important to reduce the refrigerant flow noise. To date, this problem has been investigated on the basis of trial and error. Fundamental cause and mechanism of the flow noise must be analyzed before a drastic reduction of noise can be achieved. In this study, air-water two-phase flow was used to create a slug flow with single large gas bubble for the purpose of modeling the problem. We investigated the relations among gas bubble state, static pressure pulsation and flow noise caused by single gas bubble passing through the orifice, In the results, it is shown that the noise level increases twice while the gas bubble passes through the orifice and that there exist correlations among flow state, static pressure pulsation and flow noise.
Noise problems caused by two-phase flows in tubes connected to air-cooled heat exchangers have become more serious, since the level of air conditioner fan noise has decreased. In particular, when a slug flow occurs, the noise level greatly increases. In this study, an air-water two-phase flow was used to create a slug flow through a capillary tube in order to investigate the mechanism of the noise. We also investigated the relationship between the gas bubble state and the pressure pulsation by changing the void fraction. The results show that the pressure pulsation level, which is proportional to the noise level, is determined by the magnitude and the density of the impact pressure pulsation caused by the expansion of the gas at the end of the capillary tube.
Gas bubbles, when entrained in water or other liquid, can generate high sound pressures in the liquid. Significant sound pressures are associated only with volume pulsations of the bubble, whereas oscillations in the shape of the bubble do not result in appreciable sound. Calculations have been made of the sound pressures resulting from excitation of volume pulsations by the following mechanisms: by bubble formation,coalescence, or division; by the motion of a free stream of liquid containing entrained bubbles past an obstacle; and by the flow of liquid containing entrained bubbles through a pipe past a constriction. The calculation of the sound pressuregenerated by bubble formation has been verified by measurements with bubbles formed at a nozzle.
Transitions for vertical upflow of gas-liquid systems are modeled. A
method for predicting transitions is soundly based on the results of the
work. With the initial conceptual studies of the transient flow regime
behavior complete in this report, it will be possible to write computer
programs to explore the ideas in the second report of the study.
Two-phase gas-liquid flow has been investigated in a l-inch internal diameter vertical tube coil containing two risers and a downcomer all connected by ″U″ bends. Flow pattern data were obtained in the three vertical tubes, each 17. 30 ft long, for five different air-liquid systems at about 25 psia over flow ranges of 0-700 lb//m air/min-ft**2 and 140-25300 lb//m liquid/min-ft**2. Liquid phase viscosities ranged from 1 to 12 cp. A flow pattern classification with six regimes including coring-bubble, bubble-slug, falling film, falling bubbly-film, froth and annular flow regimes was established for downflow. Flow patterns in the bends were also classified. Data from the present investigation were used to formulate an empirical flow pattern graphical correlation for both upflow and downflow. The transitions between one flow pattern and another occur gradually. Similarity exists between the upflow and downflow configurations only in the annular-mist regime. The phenomenon of coring of gas bubbles is found to occur only in downflow and is explainable by the existence of a lift force on the bubbles. The flow patterns which occur in bends are largely explained by the interaction of gravitational and centrifugal forces.
Study of Noise Reduction of Refrigerant for Capillary Tube in the Refrigerator, 32nd Conference Journal of Refrigeration and Air-Conditioning Association
- S Hirakuni
- Y Smida
- H Yamamoto
- S. Hirakuni
S. Hirakuni, Y. Smida and H. Yamamoto, Study of
Noise Reduction of Refrigerant for Capillary Tube
in the Refrigerator, 32nd Conference Journal of Refrigeration and Air-Conditioning Association. 4
(1998) 22-24.