Experimental analysis for reducing refrigerant-induced noise of 4-way cassette type air conditioner

한형석,정의봉,Shigeo Aoyama,모진용 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.5

Various refrigerant flow patterns can produce a range of noise types according to their cycle conditions. Consequently, the identification of flow patterns in a tube is crucial to reducing refrigerant-induced noise. Because of the obstacles involved in identifying them accurately by experiment, in this paper, these flow patterns are estimated from the flow pattern map. Working from the assumption that the refrigerant-induced noise for an air conditioner in the heating mode comes from slug flow in the condenser-outlet pipe, the reduction of refrigerant-induced noise by avoiding slug flow in a tube is examined. To fully understand the conditions under which the refrigerant-induced noise occurs, cycle simulator equipment for an outdoor unit is developed. With this cycle simulator, noise tests of 4-way cassette type indoor units are performed under the conditions that the refrigerant-induced noise occurs. Increasing the mass flux in a tube by reducing the diameter of the condenser-outlet pipe can avoid slug flow, and the refrigerant-induced noise can therefore be reduced. The results of the cycle simulator can be verified with an outdoor unit 5HP system multi air conditioner and the results are well in line with simulator results.

Development of noise pattern map for predicting refrigerant-induced noise in refrigerators

김민성,정의봉,한형석 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.9

In refrigeration systems, flow state in evaporators is two-phase. Acoustic characteristics of noise generated in pipes with two-phaseflow depend on flow patterns and instantaneous cycle conditions. Refrigerant-induced noises are irregular and have a band frequency. Therefore, it is difficult to predict the occurrence conditions of refrigerant-induced noise in evaporators. Hence, the development of adesign guide that anticipates the occurrence of refrigerant-induced noise is important. Flow pattern maps have been proposed by Baker,Hewitt, Taitel-Dukler, etc. However, these do not consider the acoustic viewpoint and cannot predict refrigerant-induced noise basedsolely on the estimated flow patterns. Therefore, in this study, we suggest a noise pattern map for directly anticipating refrigerant-inducednoise from various flow patterns. We performed experiments using R600a refrigerant and refrigerant-supply equipment designed for flowvisualization and flow regime transition. Based on experimental data, we suggest a noise pattern map for determining the level of refrigerant-induced noise.

Experimental Study of the Effects of the Cycle Characteristics on the Refrigerant-Induced Noise in System Air-Conditioner

Weui Bong Jeong,Hyung Suk Han,Jin Yong Mo,Jae Kwon Lee 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.7

The main sources of the refrigerant-induced noise can be classified 2 types according to its characteristics. One is due to the cyclic characteristics such as quality, velocity of the refrigerant, pressure drop and mass flow rate. The other is due to the structural characteristics such as distributed path pipe layout, distributor and expansion device. In this paper, the effects of cycle characteristics on the noise of multi-type system air-conditioner are investigated experimentally. In the indoor unit of multi-type air-conditioner, the variation of noise is examined when the in-flowing and out-flowing refrigerant to the indoor unit are 2-phase state according to its cycle control. And several factors are recommended in order to reduce the refrigerant-induced noise of the air-conditioner.

Analysis of the root causes of refrigerant-induced noise in refrigerators

한형석,정의봉,김민성,김태훈 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.12

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.

Reduction of the Refrigerant-Induced Noise from the Transition of Flow Pattern by Decreasing Tube Diameter

Takushima, Akira,Han, Hyung-Suk,Jung, Wei-Bong The Society of Air-Conditioning and Refrigerating 2009 International Journal of Air-Conditioning and Refr Vol.17 No.2

It is well known that a refrigerant-induced noise is caused by two-phase flow in the indoor unit of a heat pump air-conditioner. Especially when the flow pattern in a pipe is intermittent flow, the irregular noise occurs frequently. But it is very difficult to avoid this kind of the noise for the application of air-conditioner. Therefore, in this research, the flow patterns at two-phase flow state in a pipe of the indoor unit for the air-conditioner are researched using cycle simulator at typical cycle conditions. In order to find the relationship between refrigerant-induced noise and flow pattern, the noise patterns are investigated with respect to the estimated flow pattern from the various flow pattern maps. Base on the estimations of the flow patterns by those maps, the refrigerant-induced noise is evaluated as decreasing tube diameter, which can transit the flow pattern from slug to annular flow.

Flow visualization and noise measurement of R410A two-phase flow near electric expansion valve for heating cycle of multi-split air-source heat pump

Kim, Gangjune,Lee, Jaehong,Park, Junhong,Song, Simon Pergamon 2019 Applied thermal engineering Vol. No.

<P><B>Abstract</B></P> <P>Multi-split air-source heat pumps (ASHPs) have been widely used for both heating and cooling. An electric expansion valve (EEV) is frequently positioned in the indoor unit (IDU), leading to an increase in the two-phase flow noise of the refrigerant. In this study, we experimentally investigated the two-phase flow patterns and flow-induced noise of R410A refrigerant near the EEV in an IDU during the heating cycle of a multi-split ASHP with four IDUs. The flow-induced noise and two-phase flow patterns of horizontal and vertical pipe layouts near the EEV were simultaneously measured under a transient operation condition of temperature (24–38 °C), pressure (1.7–2.7 MPa), and mass flowrate (6.2–41.9 kg/h). The big noise near the EEV was generated for an intermittent flow and a churn/slug flow pattern at the EEV inlet for both horizontal and vertical pipe layouts, respectively. Unlike refrigerators and cooling air-conditioners, a vertical pipe layout has two-phase flow patterns that are advantageous for noise reduction near the EEV because of the high operating mass flux and pressure for R410A of a heating cycle of a multi-split ASHP. The two-phase flow-induced noise of the refrigerant near the EEV was strongly affected by the flow patterns at the EEV’s inlet and outlet. The present study indicates that the flow patterns affected by pipe layout, phase properties, and operating conditions should be considered as one of the important factors in designing a refrigerant system of reduced noise.</P> <P><B>Highlights</B></P> <P> <UL> <LI> R410A two-phase flow of multi-split air-source heat pump cycle was studied. </LI> <LI> Two-phase flow visualization and noise measurement were simultaneously performed. </LI> <LI> Vertical pipe layout resulted in 3 dB lower noise level than horizontal layout. </LI> <LI> Effect of flow pattern on two-phase flow noise overwhelmed those of pipe layout. </LI> </UL> </P>

에어컨 실내기 냉매 소음의 정량적 평가 인덱스 개발

정운창(Un-Chang Jeong),오재응(Jae-Eung Oh) 한국소음진동공학회 2019 한국소음진동공학회 논문집 Vol.29 No.4

In this study, the objective and subjective sound quality of refrigerant-induced noise from air conditioner indoor units are conducted, particularly on the noise of two-phase flow, which is the main refrigerant-induced noise in air conditioner indoor units. To this end, Zwicker’s parameters were determined for an objective evaluation of two-phase flow noise via signal processing. In addition, virtual sound sources were produced such as the amplification of noise level, frequency shift, and increase/decrease in playback time. Sound quality evaluation was performed on the virtual sound sources, and a multiple regression equation was established using the objective evaluation parameters. Finally, a sound quality index with more than 90 % reliability is established through statistical processing and objective and subjective sound quality assessment of virtual sound.

냉장고 증발기 배관의 2상유동양식 예측 및 소음 평가

허소정(Heo, So-Jung),김민성(Kim, Min-Seong),한형석(Han, Hyung-Suk),정의봉(Jeong, Weui-Bong) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.10

The refrigerant after the expansion valve interchanges the heat at the evaporator. At this moment, the state of gas and liquid becomes two-phase flow and causes irregular noise. In order to avoid the noise, the two-phase flow pattern should be predicted. In this paper, the procedure to predict the two-phase flow patterns such as churn flow and annular flow was suggested using the CFD software. The experiments using refrigerant-supplying equipment was carried out and the noise levels according to the flow pattern were measured. The flow patterns predicted by this procedure showed good agreement with those by experiments. The churn flow is noisier than annular flow pattern.

소형 냉동시스템 소음의 구조와 유동 연성 분석과 저감 방안

김수현(Kim, Soo-Hyun),이동연(Lee, Dong-Yeon),이무연(Lee, Moo-Yeon) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.11

본 논문의 목적은 가정용 냉동시스템에서 유발되는 소음 및 진동을 소음 및 진동 분석 방법에 의거하여 파 악하여 궁극적으로 소음제어를 통하여 저감하는 것이며 소음저감 방안을 제공하는데 있다. 이를 위하여 다양한 냉동 시스템의 작동 조건에서 구조 소음 및 유동 소음을 측정하였으며, 압축기 및 주요 구성부품들에 대한 소음 제어를 통 하여 10%의 소음을 저감하였다. This paper addresses how to reduce or redesign uncomfortable sound from small refrigerator by modifying some structures in mechanical components or operating conditions. After performing vibration analysis on each component and then sound analysis are carried out. From stepped designed experiments, we could acquire some important results that structure and flow induced vibration assumed to be a major cause to noise level and frequencies. Modifying some mechanical structure and operating conditions, uncomfortable starting noise and beating sound are suppressed. Machinery room located in refrigerator’s backside is investigated for vibration and noise suppression, and some ideas for more improvement are suggested

냉장고 냉매소음 저감을 위한 단열 발포재의 진동 전달특성 분석

한형석(Han, Hyung-Suk),김민성(Kim, Min-Sung),정의봉(Jeong, Weui-Bong),서민영(Seo, Min-Young),이수영(Lee, Soo-Young) 한국소음진동공학회 2010 한국소음진동공학회 논문집 Vol.20 No.1

In the refrigerator, the two-phase refrigerant-induced noise of the capillary tube in an evaporator-inlet pipe has been a great concern. The capillary tube is usually covered with insulation-foam packed in the space between inner and outer cabinets without any vibration isolation. Therefore, the refrigerant-induced vibration of the capillary tube can be easily transferred to the outer cabinet, which may increase the radiated noise. In this paper, the characteristics of transferred vibration through the insulation-foam are investigated experimentally by using the refrigerantsupplying equipment. The frequency characteristics, such as dynamic Young's modulus and loss factor, of the insulation-foam are also discussed.