• Title/Summary/Keyword: 압력강하

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Constructal study on optimizing the pressure drop of the flow channel configurations with two diameters (형상법칙을 이용한 트리구조의 압력강하 최적화 연구)

  • Cho, Kee-Hyeon;Lee, Jae-Dal;Kim, Moo-Hwan
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2652-2657
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    • 2008
  • An analytical study was carried out on the flow resistance of tree-shaped channel flow architectures, based on the principle of the constructal law of evolutionary increase of flow access through the generation of better flowing configurations with two diameters in the square domain. Two types of tree-shaped configurations are optimized. The minimized global flow resistance decreases definitely as the system size, N, increases. And the best channel configurations among the first construct and second construct as a result of regarding pressure drop was selected. We also show that the freedom to morph the design and to increase its performance can be enhanced by using tree-tree configurations with $2^{nd}$ construct when N is greater than 18.

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Experimental Investigation on the Pressure-Drop Instabilities in Boiling Channel (비등유로의 압력강하 불안정성에 대한 실험적 고찰)

  • Kim, B.J.;Shin, K.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.5 no.3
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    • pp.179-186
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    • 1993
  • The characteristics of pressure-drop oscillations(PDO) in boiling channel are studied experimentally. The effects of initial and boundary conditions on PDO are investigated in terms of oscillation period and amplitude. The period and amplitude of PDO are increased with the increase in the compressible volume in surge tank and heat input. However the amplitude of PDO is decreased with fluid temperature under low subcooling condition. Higher initial insurge flowrate resulted in almost invariant oscillation period but lower amplitude. At higher heat input the oscillation of heater wall temperature is significant, whose period is the same as that of pressure-drop instability.

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Experiments on Condensation Heat Transfer and Pressure Drop in Plate Heat Exchangers with Different Chevron Angles (판형 열교환기의 세브론각에 따른 응축열전달 및 압력강하 실험)

  • 김윤호;한동혁;이규정
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.11
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    • pp.1141-1148
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    • 2001
  • Experiments on the condensation heat transfer and pressure drop in the brazed type plate heat exchangers are performed with refrigerants R410A/R22. To investigate the geometric effect, plate heat exchangers with the same pitch and height but different $45^{\circ},\;35^{\circ}and\;20^{\circ}$ chevron angles are used. Varying the mass flux of refrigerant (13~34 kg/$m^2$), the condensing temperatures ($20^{\circ}C\;and\;30^{\circ}C$) and the vapor quality (from 0.9 to 0.15) at the same constant heat flux ($5kW/m^2$), the condensation heat transfer coefficients and pressure drops are measured. The heat transfer coefficients decrease slightly with increasing the condensing temperature at a given mass flux in all plate heat exchangers. The pressure drop increases with increasing the mass flux and the quality and decreasing the condensing temperature and the chevron angle.

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Evaluation of Air-side Heat Transfer and Friction Characteristics on Design Conditions of Condenser (응축기의 설계조건에서 공기측 열전달계수 및 압력강하 산출)

  • 김창덕;전창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.3
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    • pp.220-229
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    • 2003
  • An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150~250 kg/$m^2$s with air flows at velocity ranges from 0.6 m/s to 1.6 m/s.

Characteristics of Pressure Drops in Square Channels with Twisted Tape Inserts plus Axial Interrupted Ribs (테이프와 거칠기가 설치된 사각 채널의 압력강하 특성)

  • Ahn, S.W.;Bae, S.T.;Kang, H.K.
    • Journal of Power System Engineering
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    • v.10 no.4
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    • pp.38-42
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    • 2006
  • Pressure drops and friction factors in square channels with twisted tape inserts plus axial interrupted ribs are investigated. Tests are performed for Reynolds numbers ranging from 8,900 to 29,000. The rib height-to-channel hydraulic diameter, $e/D_h$, is kept at 0.057 and test section length-to-hydraulic diameter, $L/D_h$ is 30. The pressure drops and friction factor values are enhanced with axial interrupted ribs and twisted tape inserts. Square channels with twisted tape inserts plus axial interrupted ribs show the greatest pressure loss penalty in the present work. Friction factor data obtained for the square channel with twisted tape inserts plus axial interrupted ribs are less than those in the past publications for circular tubes with axial interrupted ribs and twisted tape inserts.

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Two-phase Pressure Drop in a Horizontal Rectangular Microchannel (수평 사각 마이크로채널 내에서의 2상 유동 압력강하)

  • Huh, Cheol;Kim, Moo-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.11 s.254
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    • pp.1035-1042
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    • 2006
  • An experimental investigation was performed to study two-phase pressure drop of deionized water in a microchannel. Measurement and evaluation of two-phase frictional pressure gradient were carried out using a single horizontal rectangular microchanne1 having a hydraulic diameter of $100{\mu}m$. Tests were performed for mass fluxes of 90, 169, and 267 $kg/m^2$s and heat fluxes of 200-700 $kW/m^2$. Test results showed that the measured two-phase frictional pressure gradient increased with the mass flux and vapor quality. Most macro-channel correlations of two-phase frictional pressure gradient did not provide reliable predictions except under certain limited conditions.

Characteristics on Evaporating Pressure Drop of HCs Refrigerants inside a horizontal tube (수평관내 HC계 냉매의 증발 압력강하 특성)

  • Choi, Jun-Hyuk;Lee, Ho-Saeng;Kim, Jae-Dol;Yoon, Jung-In
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2006.06a
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    • pp.63-64
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    • 2006
  • Chracteristics on evaporating pressure drop of HCs refrigerants inside a horizontal tube were studied experimentally. Experimental results were presented for pressure drops of hydrocarbon refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 inside a horizontal double pipe heat exchanger. Three tubes with a tube diameter of 12.70mm, 9.52mm and 6.35mm were used for this study. Hydrocarbon refrigerants showed higher evaporating pressure drop than that of R-22 in all tubes. The highest pressure drop was founded in R-600a. The highest evaporating perssure drop of all refrigerants was shown in a tube diameter of 6.35mm with same mass flux. The results can be used as the basic data for the design of heat exchanger using hydrocarbon refrigerants as an alternatives.

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Pressure Drop and Heat Transfer Characteristics of Multi-Layer Screen (적층 스크린의 압력강하 및 열전달 특성)

  • Song, Tae-Ho;Ahn, Cheol-Woo;Kim, Chang-Kee;Ko, Hyun-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.3
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    • pp.419-425
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    • 2000
  • Multiple layer of wire screen is widely used in many compact devices to filter particulates and to heat or cool fluids. However, data of flow resistance and heat transfer through such layers are rare to find and thus they are experimentally investigated in this study. Compressed air is made to flow through it to find the Ergun constants over a wide range of the Reynolds number. Also, unsteady heating of the wire screen is performed to find the equivalent heat transfer coefficient between the screen and the air by fitting the unsteady air temperature. The obtained coefficients are expressed in terms of the Reynolds number and the Prandtl number.

The pressure drop characteristics in LNG heat exchanger of cryogenic cascade refrigeration cycle (초저온 캐스케이드 냉동사이클의 LNG 열교환기 압력강하 특성)

  • Yoon, J.I.;Choi, K.H.;Kwag, J.W.;Son, C.H.;Baek, S.M.
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.376-381
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    • 2012
  • Natural gas is converted in to LNG by chilling and liquefying the gas to the temperature of $-162^{\circ}C$, when liquefied, the volume of natural gas is reduced to 1/600th of its standard volume. This gives LNG the advantage in transportation. The pressure dorp of the cascade liquefaction cycle was investigated and simulated using HYSYS software. The simulation results showed that the pressure drop in the LNG heat exchanger is set to 50 kPa considering the increase in the compressor work of cryogenic cascade liquefaction cycle.

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Experimental Study on Flow Patterns and Pressure Drop Characteristics of Ice Slurry in Small Size Pipe (2) (소구경 배관내 아이스슬러리의 유동형상 및 압력강하 특성에 관한 실험적 연구(2))

  • 이동원;윤찬일;주문창
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.5
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    • pp.391-397
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    • 2002
  • Pressure drop were experimentally investigated for ice slurry flowing in the acrylic pipes with inner diameter of 24 mm. Ice slurry was made from 6.5% ethylene glycol-water solution, and the pipes is consisted of horizontal, vertical (upward and downward) and $90^{\circ}$ elbow pipe. The ice Packing factor (IPF) and the flow rate of the experiments were varied from 0 to 30% and from 5 to 70kg/min respectively The measured pressure drop in various pipe positions were compared with those for the solution flow (IPF=0). The pressure drop was larder than that for solution flows as the IPF increased when the flow rate was low or very high. Sharp increases in pressure drop were observed for the cases when IPF is more than 70% in horizontal and vertical pipes, whereas the pressure drop increased with the IPF simultaneously in an elbow pipe.