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

Akira Takushima,HyungSuk Han,WeiBong Jung 대한설비공학회 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.

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 patterns in 4:1 micro-contraction flows of viscoelastic fluids

이대웅,안경현 한국유변학회 2015 Korea-Australia rheology journal Vol.27 No.2

In this paper, the flow pattern of viscoelastic fluids flowing inside a 4:1 planar contraction microchannel was investigated and quantitatively analyzed. A wide range of Weissenberg number flows of poly(ethylene oxide) solutions were observed while maintaining low Reynolds number (0.01 > Re). As the shear rate or fluid elasticity was increased, a transition from steady to unsteady flow was observed. In the steady flow region, the flow pattern was Newtonian-like, progressed to a divergent flow where the upstream flow pattern was distorted due to elasticity, and then a vortex developed at the upstream corners. The vortex, which was stable at first, fluctuated with a certain period as the Weissenberg number increased. The oscillating vortex was symmetric at first and became asymmetric with various patterns. As the elasticity increased further, the vortex randomly fluctuated without any time period. The Lyapunov exponent for the change in vortex size was positive, meaning that the flow was spatially chaotic. This paper systematically analyzed the flow patterns of the elastic fluids in the micro-contraction flow, which included; Newtonian-like flow, divergent flow, oscillating flow with symmetry, oscillating flow with asymmetry, and chaotic flow

二相 流動場에서 流動樣式 判別에 關한 硏究

박근욱,오율권 조선대학교 생산기술연구소 1998 生産技術硏究 Vol.20 No.1

The analysis of single phase flow is made easier if it can be established that the flow is either lamina or turbulent and whether any separation or secondary flow effect occurs. The information is equally useful in the study of gas-liquid flow. However, perhaps of greater importance in the latter case is the topology or geometry of the flow. When a liquid is vaporized in a heated channel the liquid and vapour generated take up a variety of configurations known as flow pattern. The particular flow pattern depends on the condition of pressure, flow, heat flux. and channel geometry. Each has a descriptive name and in the design of a heat exchanger it is desirable to know what the flow pattern or successive flow pattern are so that a hydrodynamic of heat transfer theory appropriate to that pattern can be chosen. The purpose of the present work is that flow pattern was discriminated by probability density functions corresponding to the statical measurement for electrical conductivity probe signal and flow visualization

水平 2相 流動場에서 流動樣式判別에 關한 硏究

金在根,吳栗權,車京玉 明知大學校 産業技術硏究所 1996 産業技術硏究所論文集 Vol.15 No.-

The analysis of single phase flow is made easier if it can be established that the flow is either laminar or turbulent and whether any separation or secondary flow effect occurs. This information is equally useful in the study of gas-liquid flow. However, perhaps of greater importance in the latter case is the topology or geometry of the flow. When a liquid is vaporized in a heated channel the liquid and vapour generated take up a variety of configurations known as flow patterns. The particular flow pattern depends on the conditions of pressure, flows, heat flux and channel geometry Each has a descriptive name and in the design of a heat exchanger it is desirable to know what the flow pattern or successive flow patterns are so that a hydrodynamic of heat transfer theory appropriate to that patterns can be chosen. The purpose of the present work is that flow pattern was discriminated by probability density functions corresponding to the statical measurement for electrical conductivity probe signal and flow visualization.

Flow Visualization of Oscillation Characteristics of Liquid and Vapor Flow in the Oscillating Capillary Tube Heat Pipe

Kim, Jong-Soo,Kim, Ju-Won,Jung, Hyun-Seok The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.10

The two-phase flow patterns for both non-loop and loop type oscillating capillary tube heat pipes (OCHPs) were presented in this study. The detailed flow patterns were recorded by a high-speed digital camera for each experimental condition to understand exactly the operation mechanism of the OCHP. The design and operation conditions of the OCHP such as turn number, working fluid, and heat flux were varied. The experimental results showed that the representative flow pattern in the evaporating section of the OCHP was the oscillation of liquid slugs and vapor plugs based on the generation and growth of bubbles by nucleate boiling. As the oscillation of liquid slugs and vapor plugs was very speedy, the flow pattern changed from the capillary slug flow to a pseudo slug flow near the annular flow. The flow of short vapor-liquid slug-train units was the flow pattern in the adiabatic section. In the condensing section, it was the oscillation of liquid slugs and vapor plugs and the circulation of working fluid. The oscillation flow in the loop type OCHP was more active than that in the non-loop type OCHP due to the circulation of working fluid in the OCHP. When the turn number of the OCHP was increased, the oscillation and circulation of working fluid was more active as well as forming the oscillation wave of long liquid slugs and vapor plugs in the OCHP. The oscillation flow of R-142b as the working fluid was more active than that of ethanol and the high efficiency of the heat transfer performance of R -142b was achieved.

Effects of plate angle on flow bifurcations and heat transfer characteristics in a channel with inclined plates

Zhan, Yinxiao,Park, Tae Seon Elsevier 2016 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.97 No.-

<P><B>Abstract</B></P> <P>Oscillatory flows and heat transfer characteristics in a channel with inclined plates have been numerically investigated. For the fully developed channel flow of 10 ⩽ Re ⩽ 800 , the inclined plates as a vortex generator are installed at the upper wall. To examine the effects of inclined plates on flow bifurcation and attendant heat transfer rates, unsteady simulations are performed for various plate conditions. The resulting flows are classified into three vortical structures of recirculation bubble (RB), standing vortex (SV), and traveling vortices (TV) depending on the Reynolds number and geometrical conditions. The variation of flow pattern is closely related to the spectral characteristics of steady state, periodic state, and quasi-periodic state. Based on these flow patterns and unsteady features, the transition scenario is proposed with increasing the plate angle. The flow is evolved from the steady state to the periodic and quasi-periodic state, and the frequency-locking phenomenon is observed for specific Reynolds numbers at a certain range of plate angle. In addition, the heat transfer enhancement is discussed with flow patterns and unsteady characteristics. The Nusselt numbers continuously increases from the steady state of RB to the periodic state of SV, while their variations are discontinuous when the periodic state of SV is changed into the quasi-periodic state of TV. The flow analyses show that these discontinuities are related to the supercritical Hopf bifurcation and the additional appearances of fundamental frequency. Also, the frequency-locking state before the development of quasi-periodic state with multiple frequencies brings about a jump increase of heat transfer. The disturbed flows by the inclined plates exhibit the logarithmic variation and Nusselt number correlation similar to the transition flow.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oscillatory flows are characterized by three vortical structures. </LI> <LI> The discontinuous variation of <I>Nu</I> is strongly related to the quasi-periodic state. </LI> <LI> The frequency-locking phenomenon depends on the flow development with multiple frequencies. </LI> <LI> The disturbed flows exhibit Nusselt number correlations similar to the transition flow. </LI> </UL> </P>

조선시대 직물의 곡수문(曲水紋) 유래와 전개 양상

강서영,안보연 한국의류학회 2023 한국의류학회지 Vol.47 No.2

Patterns abstractly depicting flowing water with Chinese characters such as gong, wan(man), or wang con- tinued endlessly and curved water patterns began appearing on textiles during the Song Dynasty. Though Song curved water patterns encompassed poetic sentiments such as “falling flowers and flowing water,” the meaning faded with time, and these patterns were depicted in backgrounds with flowers added to brocade (Geum-sang-cheom-hwa). During the Ming and Qing Dynasties, combinations of diverse patterns, including flowers, butterflies, dragons, and auspicious treasures became fashionable, rather than the gong- and wan-shaped curved water patterns. Likewise, during the Joseon Dynasty, curved water patterns were preferred as background rather than as primary patterns. They were overlaid with flowers and clouds. The overlaid flow- er patterns included four-season flower patterns (17th-18th centuries), round flower patterns (19th century), and large flower patterns (20th century), which were identical to flower patterns fashionable at the time and ar- ranged at intervals on complex curved water pattern backgrounds. In contrast, simple Ruyi types were more numerous than the four-Ruyi types fashionable at the time with regard to cloud patterns. Added here were Taiji (great ultimate symbol) or crane patterns, thus seeking to depict diverse auspicious Ruyi such as wish fulfill- ment and longevity.

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.

균일형 유로에서 기포의 거동에 관한 연구

정영관 한국수소및신에너지학회 2013 한국수소 및 신에너지학회논문집 Vol.24 No.1

The hydrogen or oxygen gas producted by electrolysis become many bubbles in the electrolyte, but exact data on the behavior of these bubbles in the separator of an electrolysis stack didn't become known. In this study, the flow visualization experiment on the behavior of bubbles in the flow pattern of the array type separator is performed by using of a visible alkaline electrolysis stack and a stereoscopic microscope. As the results, a fine size bubbles adhered to the surface of the flow pattern grow to large sized bubbles until each bubble's buoyance is lager than the sum of external force and weight. And then the large bubbles flow into the upper area of the separator. Bubbles adhered to the surface of the vertical flow pattern grow quickly than them adhered to the surface of the horizontal flow pattern. Also, he electrolysis efficiency is declined because many multi-size bubbles occupied the wide volume in the flow pattern.