• Title/Summary/Keyword: 압력강하

Search Result 779, Processing Time 0.2 seconds

Pressure Drop in a Helical Square Duct (나선형 사각덕트 내의 압력강하)

  • Ryu, Seung-Yeob;Yoon, Juh-Yeon;Lee, Doo-Jeong
    • Proceedings of the KSME Conference
    • /
    • 2001.06e
    • /
    • pp.398-403
    • /
    • 2001
  • Pressure drop at a helical square duct orifice is numerically evaluated. The orifice is installed at the entrance of a once-through steam generator tube to suppress flow instabilities. The calculated results are compared with the available experimental correlations, and showed good agreement. Effects of curvature ratio and characteristics of the secondary flow with Reynolds number are reported. Through the numerical simulations, pressure drop mechanisms were well understood inside the compact and complicated orifice geometry.

  • PDF

Study on Evaporation Pressure Drop of Hydrocarbon Refrigerants (탄화수소계 냉매의 증발 압력강하 특성에 관한 실험적 연구)

  • Lee Kwang-Bae;Lee Ho-Saeng;Kim Jae-Dol;Yoon Jung-In
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.29 no.5
    • /
    • pp.533-539
    • /
    • 2005
  • Experimental results are presented for heat transfer and pressure gradients of HCs refrigerants R-290, R-600a, R-1270 and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers. Two tubes with a tube diameter of 12.70mm and 9.52mm are used for this investigation. Hydrocarbon refrigerants have higher pressure drop than R-22 in 12.7mm and 9.52mm. The results from the investigation can be used in the design of heat transfer exchangers using hydrocarbons as the refrigerant for the air-conditioning systems.

A Study on Heat Transfer and Pressure drop Characteristics in Plate Heat Exchange (판형 열교환기의 열전달 및 압력강하 특성에 관한 연구)

  • 서무교;박재홍;김영수
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.25 no.3
    • /
    • pp.581-587
    • /
    • 2001
  • Plate heat exchange(PHE) will be applied to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. The purpose of this study is the analyze the characteristics of heat transfer and pressure drop of plate heat exchanger. Numerical work was conducted using the FLUENT code k-$\varepsilon$model. Also the dependence of heat transfer coefficient and friction factor on Reynolds number was investigated. As the Reynolds number increases, it is found that heat transfer coefficient also increases, but friction factor decreases. The study examines the internal flow, thermal distribution and the pressure distribution in the channel of plate heat exchanger. The results of CFD analysis compared with experimental data, and the difference of friction factor and Nusselt number in plate heat exchanger are 10% and 20%, respectively, Therefore the CFD analysis model is effective for the performance prediction of plate heat exchanger.

  • PDF

Experimental Study on Heat Transfer and Pressure Drop Characteristics for Single-Phase Flow in Plate and Shell Heat Exchangers. (Plate and Shell 열교환기의 단상유동 열전달 및 압력강하 특성에 관한 실험적 연구)

  • 서무교;김영수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.12 no.4
    • /
    • pp.422-429
    • /
    • 2000
  • Plate and shell heat exchanger(P&SHE) is widely applied as evaporators or condensers in the refrigeration and air conditioning systems for their high efficiency and compactness. In order to set up the database for the design of the P&SHE, heat transfer and pressure drop characteristics for single phase flow of water in a plate & shell heat exchanger are experimentally investigated in this study. Single phase heat transfer coefficients were measured for turbulent water flow in a plate and shell heat exchangers by Wilson plot method. The shell side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a plate side were obtained by Wilson plot method. Single-phase heat transfer correlations based on projected heat transfer area and friction factor correlations have been proposed for single phase flow in a plate and shell heat exchanger.

  • PDF

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

  • 김창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.15 no.12
    • /
    • pp.1007-1017
    • /
    • 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 and wet 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 0.3 m/s to 0.8 m/s.

Experimental Studies on Heat Transfer and Pressure Drop Characteristics during Gas Cooling Process of Carbon Dioxide in the Supercritical Region (이산화탄소의 초임계 가스냉각 과정의 열전달 및 압력강하 특성에 관한 실험적 연구)

  • 윤석호;김주혁;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.16 no.6
    • /
    • pp.538-545
    • /
    • 2004
  • This paper presents the experimental data for the heat transfer and pressure drop characteristics obtained during the gas cooling process of carbon dioxide in a horizontal tube. The tube in which carbon dioxide flows is made of copper with an inner diameter of 7.73 mm. Experiments were conducted for various mass fluxes and inlet pressures of carbon dioxide. Mass fluxes are controlled at 225, 337 and 450 kg/$m^2$s and inlet pressures are adjust-ed from 7.5 to 8.8 ㎫. The experimental results in this study are compared with the existing correlations for the supercritical heat transfer coefficient, which generally under-predict the measured data. Pressure drop data agree very well with those calculated by the Blasius' equation. Based on the experimental data, a new empirical correlation to estimate the near-critical heat transfer coefficients has been developed.

Flow Rate-Pressure Drop Characteristics of Dispersive ER Fluid According to Change of Electric Field Strength in Clearance between Parallel Plates (평행평판 간극에서 전기장의 강도변화에 따른 분산계 ER유체의 유량-압력강하 특성)

  • 장성철;염만오;김도태
    • Transactions of the Korean Society of Machine Tool Engineers
    • /
    • v.12 no.1
    • /
    • pp.78-83
    • /
    • 2003
  • Electro-rheological(ER) fluids are suspensions in which rheological properties show an abrupt change with variation of electric fields. We modeled the parallel-plates relating to ER-Valve system and yielded shear stress according to the strength of electric field. The purpose of the present study is to examine the flow characteristics of ER fluids according to the strength of electric field between parallel-plates. Then the steady relationship between pressure drop and flow rate of the ER fluids between parallel-plates under application of an electric fields was measured. The pressure drop and flow rates of ER fluids under the application of electric fields for steady flow were measured. For the experiment, we used the ER fluids, 35w% zeolite having hydrous particles and differential pressure gauge. This test reviewed experiment for the special changes of ER fluids in the steady flow condition.

Prediction of Pressure Drop in Venturi Scrubber Using the Eulerian - Lagrangian Method (오일러-라그랑지 방법을 이용한 벤튜리 스크라버의 압력강하 계산)

  • Pak S, I.;Moon Y. W.;Chang K. S.
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2004.03a
    • /
    • pp.190-195
    • /
    • 2004
  • The pressure drop in a Venturi Scrubber is predicted using the Eulerian-Lagrangian Method, which is one of the numerical methods to solve the dispersed two-phase flow. KIVA-3V Code is modified to solve the coupled gas-liquid two-phase flow field. The liquid is assumed to be injected through the nozzles with the Rosin-Rammler drop size distribution. The computational results shows good agreement with the experimental data.

  • PDF

Evaluation of Heat Transfer Enhancement Performance for Wire Coil Inserts in Horizontal Smooth Tubes (수평 평활관 내부에 삽입한 와이어코일 인서트에 대한 전열성능평가)

  • 남상철;이주동;이상천
    • Journal of Energy Engineering
    • /
    • v.9 no.3
    • /
    • pp.202-211
    • /
    • 2000
  • 본 연구는 다양한 각도를 가지는 와이어코일을 사용하여 관내 단상 열전달 촉진 및 압력강하 특성 실험을 수행하였다. 작동유체는 순수 물과 에틸렌글리콜을 체적비율로 50% 혼합하여 사용하였으며, 시험부 관지름은 11mm와 13.88mm이고, 시험부 길이는 760mm를 사용하였다. 평활관과 와이어코일을 삽입한 열전달촉진관에 대한 관내 열전달계수와 마찰계수는 실험에서 측정한 온도, 유량, 압력강하 값을 기초로 구하였다. 와이어코일에 대한 거친표면해석을 수행하였으며, 그 결과를 거칠기 래이놀즈수에 대한 운동량전송 거칠기함수와 열전달 거칠기함수로 표현하였으며 이에 대한 상관식을 제시하였다. 이 상관식들은 거칠기 레이놀즈수, 코일 각도, 프란틀수의 함수로 표현하였다.

  • PDF

An Experimental Study on Heat Transfer and Pressure Drop of Air Side in a Plate-Louvered Fin Heat Exchanger (평판관-루버핀 열교환기의 공기측 열전달 및 압력강하 특성에 관한 실험적 연구)

  • 강병하;김석현;장혁재;박병규
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.14 no.6
    • /
    • pp.485-492
    • /
    • 2002
  • Heat transfer and pressure drop on the air side of a plate-louvered fin heat exchanger with new shape of louver fin have been investigated experimentally. Water is employed inside the flat tube to transfer heat with air for convenience. This problem is of particular interest in the design of a plate-louvered heat exchanger. The effect of air flow rate, water flow rate and water temperature on pressure drop as well as heat transfer in air side are studied in detail. The present results showed a good agreement qualitatively with the previous results in general. Based on the experimental data, f-factor and j -factor correlations of the present louvered-fin are suggested. It is also found that heat transfer could be enhanced with new shape of louver fin, compared with the conventional louvered-fin, while the f-factor remains unchanged.