• Title/Summary/Keyword: Confined Jet Flow

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A Numerical Study of Turbulent Flow and Heat Transfer due to Slot-jet impinging on a Moving flat plate (이동평판에 작용하는 슬롯 충돌제트의 유동 및 열전달에 관한 수치적 연구)

  • Lee, Jong-Seok;Kim, Dong-Keon;Kim, Moon-Kyung;Yoon, Soon-Hyun;Kim, Bong-Hwan
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2798-2803
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    • 2008
  • The confined slot air jet impinging normally on a moving flat surface has been investigated numerically by using commercial CFD code Ansys CFX-V11. Turbulent flows are modeled using k-w turbulence model. Two-dimensional turbulent flow is considered. Calculations were conducted for a nozzle-to-plate spacing of eight slot nozzle width, at three Reynolds number(Re=4500, 6700 and 10,000) and four surface-to-velocity ratios i.e. 0, 0.25, 0.5 and 1. Results are compared against corresponding cases for heat transfer from a stationary plate. Local Nusselt number is calculated under constant wall temperature condition. The analysis reveals that the average Nusselt number increases considerably with the jet exit Reynolds number, but decrease with the plate velocity.

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Numerical Analysis of Recirculating Flow of a Confined Jet in a Circular Pipe (管內噴流 에서의 循環流 에 대한 수치해석)

  • 이충구;서정윤
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.9 no.1
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    • pp.64-70
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    • 1985
  • Fully Reynolds Stress model is applied to predict recirculation pattern, velocity and Reynolds shear stress distributions in a circular jet coaxially confined in a round pipe. It is found that the generation of velocity region depends on Curtet number(Ct). It is also found that the Reynolds shear stress and velocity distributions in the inital jet region depend strongly on the Curtet number up to about X/D = 2.0 but they are almost independent of the Curtet number further downstream.

Numerical Study on the Cooling Characteristics of Pedestal Heat Source with an Confined Air Jet (제한벽이 있는 공기제트에 의한 돌출 발열체의 냉각 특성에 대한 수치 해석 연구)

  • Choi, In-Su
    • Journal of the Korean Society of Industry Convergence
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    • v.12 no.1
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    • pp.11-18
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    • 2009
  • The air flow and heat transfer characteristics of an air jet impinging on a pedestal heat source has been investigated numerically to examine the effects of geometric parameters such as nozzle-to-pedestal spacing, nozzle diameter and pedestal size. Also, the parameters of Reynolds number, air jet power, supplied heat and thermal conductivity of pedestal have been studied to reveal how these affect the average Nusselt number. Hence, a two-dimensional turbulent model has been developed and adopted to simulate the fluid flow and heat transfer phenomena numerically. The results obtained from the model show that the nozzle-to-pedestal spacing, relative size of nozzle to pedestal and Reynolds number of air jet have a significant influence on the cooling characteristics of heated pedestal. Furthermore, some useful guidelines could be given to the application of cooling the heated pedestal.

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Numerical Analysis on the Heat Transfer Characteristics of Multiple Slot Jets at the Surface of Protruding Heated Blocks (충돌제트의 간격변화에 따른 발열블록 표면에서의 열전달 특성에 관한 수치해석)

  • 박시우;정인기
    • Journal of Advanced Marine Engineering and Technology
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    • v.27 no.2
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    • pp.229-237
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    • 2003
  • The flow and heat transfer characteristics at the surface of two-dimensional protruding heated blocks using confined impingement multiple slot jets were computationally investigated Numerical predictions were made for round-edged nozzles at several nozzle-to-target plate spacings and jet-to-jet distances, with turbulent jet Reynolds numbers ranging from 2000 to 7800. The commercial finite-volume code FLUENT was used to solve the heat transfer characteristics and flow fields using a RNG $\textsc{k}-\varepsilon$ model. The computed heat transfer characteristics at the surface of heated blocks were in good qualitative agreement with previous experimental data The results of heat transfer characteristics on the surface of protruding heated blocks are important considerations in electronics Packaging design.

Experimental Study of Droplet Characteristics Related to Electrospray Mode (정전분무모드에 관한 액적특성의 실험적 연구)

  • Kim, Ji Yeop;Lee, Doe Hyun;Cho, Ju Hyung;Hong, Jung Goo
    • Journal of ILASS-Korea
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    • v.27 no.1
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    • pp.26-35
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    • 2022
  • Electrospray is a method of atomizing fluid using high voltage supply and capable of generating continuous flow and coherent size of droplets. Electrical system and properties of fluids has enabled electrospray to have various spray modes. However, its studies have been confined only in Cone jet, which is more stable and easier to manipulate droplets' size than other spraying modes. Therefore, it is necessary to investigate and compare other spraying modes based on experimental parameters and physical properties of fluids. This research paper identified nine different spray modes. It was found out that Sauter Mean Diameter (SMD) is proportional to flow rate of fluids and maximum difference among spray modes was 1.7 times. On the other hand, SMD standard deviation had low variations on specific flow rates of fluids. Pulsed jet mode recorded the largest SMD standard deviation, while Spindle recorded the lowest.

Numerical Analysis on the Flow Distribution in Ondol Flue Channel (산고래 온돌연도내의 유동분포에 관한 수치해석)

  • Man Man-Ki;Lee Seung Woo
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.12 no.4
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    • pp.264-274
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    • 1983
  • Two-dimensional jet flows into a couple of confined rectangular enclosures such as an Ondol flue channel and their flow distributions were analyzed by numerical graphics : rectangular space in one enclosure is vacated and the other has 8 rectangular small posts. Both enclosures have a protruded inlet nozzle and on outlet on its center line. Steady state incompressible laminar viscous flow was assumed. The primitive forms of Navier-Stokes equations and continuity equation in a cartesian coordinate system were solved numerically by the Marker and Cell method for Reynolds numbers of 5, 10, 20, 30 and 40. From the numerical graphics it was found that the flow regions in both enclosures were devided into tow parts ; one part was the jet flow localized in a narrow center region of the enclosure and the other part was the very slow recirculating flow occupying the rest of the flow region in the enclosures. However there were a little differences in the shapes of jet flow in both enclosures for Reynolds numbers of 5 and 10 and also in the shapes of recirculating flows in both enclosures for all Reynolds number. Also it was found that waving flow appeared right before the outlet at Reynolds number of 20 and more.

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Streamline-Upwind Numerical Simulation of Two-Dimensional Confined Impinging Slot Jets (2차원 Confined 충돌 슬롯제트의 유선상류도식을 이용한 수치 해석)

  • Park, Tae-Hyun;Choi, Hyoung-Gwon;Yoo, Jung-Yul;Kim, Sang-Joon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.12
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    • pp.1663-1673
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    • 2002
  • In the present paper, flow and heat transfer characteristics of confined impinging slot jets have been numerically investigated using a SIMPLE-based segregated SUPG finite element method. For laminar jets, it is shown that the skin friction coefficient obtained from the present SUPG formulation approaches the grid-independent Galerkin solution inducing negligible false diffusion in the flow field when a moderate number of grid points are used. For turbulent jets, the k-$\omega$turbulence model is adopted. The streamwise mean velocity and the heat transfer coefficient respectively agree very well with existing experimental data within limited ranges of parameters.

A Numerical Study on Beat Transfer from an Aluminum Foam Heat Sink by Impinging Air Jet in a Confined Channel (충돌 공기제트에서 국한 유로 내 발포 알루미늄 방열기의 열전달 수치해석)

  • Lee, Sang-Tae;Kim, Seo-Young;Lee, Kwan-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.6
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    • pp.883-892
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    • 2002
  • A numerical study has been carried out to investigate the flow and heat transfer from an aluminum foam heat sink in a confined channel. A uniform heat flux is given at the bottom of the aluminum foam heat sink, which is horizontally placed on the heated surface. The channel walls are assumed to be adiabatic. Cold air is supplied from the top opening of the channel and exhausted to the channel outlet. Comprehensive numerical solutions are acquired to the governing Wavier-Stokes and energy equations, using the Brinkman-Forchheimer extended Darcy model and the local thermal non-equilibrium model f3r the region of porous media. Details of flow and thermal fields are examined over wide ranges of the principal parameters; i.e., the Reynolds number Re, the height of heat sink h/H, porosity $\varepsilon$and pore diameter ratio $R_{H}$.

A Simple Calculational Method by using Modified Von Mises Transformation applied to the Coaxial Turbulent Jet Mixing (유동함수를 이용한 난류제트혼합유동 계산에 관한 연구)

  • Choi Dong-Whan
    • Journal of the Korean Society of Propulsion Engineers
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    • v.9 no.2
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    • pp.97-104
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    • 2005
  • A simple but efficient grid generation technique by using the modified compressible form of stream function has been formulated. Transformation of a physical plane to a streamline plane, the Von Mises Transformation, has been widely used to solve the differential equations governing flow phenomena, however, limitation arises in low velocity region of boundary layer, mixing layer and wake region where the relatively large grid spacing is inevitable. Modified Von Mises Transformation with simple mathematical adjustment for the stream function is suggested and applied to solve the confined coaxial turbulent jet mixing with simple $\kappa-\epsilon$ turbulence model. Comparison with several experimental data of axial mean velocity, turbulent kinetic energy, and Reynolds shear stress distribution shows quite good agreement in the mixing layer except in the centerline where the turbulent kinetic energy distributions were somewhat under estimated. This formulation is strongly suggested to be utilized specially for free turbulent mixing layers in axisymmetric flow conditions such as the investigation of mixing behavior, jet noise production and reduction for Turbofan engines.

NOx Emission Characteristics in Parametrically Varied Methane-Air Coflow Flames (메탄 분류 화염에서의 연소 조건에 따른 NOx 배출 특성)

  • Lee, Sang-Han;Oh, Chang-Bo;Lee, Chang-Eon
    • 한국연소학회:학술대회논문집
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    • 2000.05a
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    • pp.35-44
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    • 2000
  • It was numerically studied that NOx emission characteristics of confined $CH_{4}$ jet flames with the variation of the diameter of inner fuel nozzle, the flow rate of $CH_{4}$ and equivalence ratio. Parabolic type equations were adopted in the calculation and GRI-2.1I mechanism was used for the chemical reaction. NOx emission index (EINOx) was introduced to evaluate NOx emission quantitatively in parametrically varied flames and the contribution of Thermal and Prompt NO mechanism was discussed. The results showed that Total EINOx varied sensitively with the variation of the flow rate of$CH_{4}$ but it was not sensitive to the variation of the diameter of inner fuel nozzle. Thermal EINOx showed the similar tendency to total EINOx and Prompt EINOx showed insensitivity to the variation of the diameter of inner fuel nozzle and the flow rate of $CH_{4}$.

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