• Title/Summary/Keyword: Impinging Round Jet

Search Result 28, Processing Time 0.019 seconds

An Experimental Study on the Frequency Characteristics of Hole Tones Generated by a Circular Jet of Low Speed Impinging on a Plate with a Round Hole (저속의 원형분류가 구멍에 충돌할 때 발생한 구멍음의 주파수특성에 관한 실험적 연구)

  • 이동훈
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.6 no.2
    • /
    • pp.34-41
    • /
    • 1997
  • The objective of this study is to investigate experimentally the frequency characteristics of the hole tones generated by a circular jet of low speed impinging on a plate with a round hole. The experimental results about the sound spectrum and the time wave of the hole tone are presented and discussed in relation with the hole type, the jet velocity and the distance of the nozzle-to-plate with a round hole. From the sound spectrum and time wave measurements, it is found that the hole tone is generated not only by an interaction of convected vortices with a round hole but also by a series of vortex shedding from jets passing through a hole. The hole tones generated by a feedback mechanism consist of many frequency stages and also have a hysteresis phenomenon like an edge tone. But the hole tones generated by a series of vortex shedding have nothing with the stage characteristics. The frequencies of hole tones are influenced by the jet velocity, the distance of the nozzle-to-plate with a round hole and the hole type.

  • PDF

Experimental Study on Turbulent Characteristics of Axisymmetric Impinging Jet with a Modified Initial Condition (초기조건의 변형에 따른 축대칭 충돌분사류의 난류특성에 대한 연구)

  • 한용운;이근상
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.17 no.12
    • /
    • pp.3166-3178
    • /
    • 1993
  • The turbulent flow characteristics of impinging jet have been investigated by the hot wire anemometry with a movable impinging wall. Turbulences were generated by the meshed jet as well as the typical round jet and their characteristics were compared, of mean velocity profiles, turbulent intensities. Reynolds stresses, similarities and their centerline flow behaviors. The meshed jet tends to make shear layer wider than the normal one in the initial region and the velocity profiles of the normal jet is rather contractive being compared with those of the meshed one near the wall. The effect of meshed exit appears only within 4D at the begining of jets and the cascading process of the meshed one marches more rapidly than that of the normal jet. The wall effects appear in the downstream of about 0.85 H to the impinging wall for every case of wall positions in both nozzles.

Numerical Analysis on the Turbulent Mixing Flow Field of $45^{\circ}$ Impinging Round Jet ($45^{\circ}$ 원형충돌분류의 난류혼합유동장에 대한 수치해석)

  • Kim, J.K.;Oh, S.H.
    • Journal of Power System Engineering
    • /
    • v.15 no.3
    • /
    • pp.38-45
    • /
    • 2011
  • The computational flow numerical analysis was introduced to predict thc turbulent characteristics in the mixing flow structure of $45^{\circ}$ impinging round jet. This analysis has been carried out through the commercial fluent software. Realizable(RLZ) k-${\varepsilon}$ was used as a turbulent model. It can be known that mean velocities analysed through RLZ k-${\varepsilon}$ turbulent model comparatively predict well the experiments and show well the elliptic shape of mixing flow structure in the Y-Z plane, but analysed turbulent kinetic energies show somewhat differently from the experiments in certain regions.

Evaluation of Turbulent Models on the Mixing Flow Structure of $45^{\circ}$ Impinging Jet by Two Round Jets (두 원형분류에 의한 $45^{\circ}$ 충돌분류의 흔합유동구조에 대한 난류모델 평가)

  • Kim, J.K.;Oh, S.H.
    • Journal of Power System Engineering
    • /
    • v.13 no.5
    • /
    • pp.34-39
    • /
    • 2009
  • In this paper, the CFD analysis using various turbulent models has been performed to evaluate which type of turbulent models can predict well the mixing flow structure of $45^{\circ}$ impinging round jet. This CFD analysis has been carried out through the commercial Fluent software. As a result, any of turbulent models cannot predict the experimental results definitely all over the flow range. However, as compared with the experimental results, the turbulent model of realizable(RLZ) k-$\varepsilon$ only predicts well in the limited range between X/$X_0=1.1$ and X/$X_0=2.0$.

  • PDF

Heat Transfer on a Heated Flat Plate by an Impinging Round Jet Using Liquid Crystal (Liquid Crystal을 이용한 원형충돌분류의 전열특성 연구)

  • 오승묵;이상준
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.16 no.8
    • /
    • pp.1566-1574
    • /
    • 1992
  • Local heat transfer characteristics for a round air jet impinging normally on a heated flat plate were experimentally investigated. The problem parameters investigated were jet Reynolds number, Re=4000,10000, and 20000, and nozzle-to-plate spacing(L/D) of 2,6, and 10. The temperature variations on the flat uniform heat flux surface were mapped using a thermo-sensitive liquid crytal sheet. The isochromatic images corresponding to the characteristic temperature of liquid crystal were analyzed with the help of a digital image processing system. The local Nusselt number, Nu decreased rapidly in the impingement region and exhibited a similar profiles in the wall jet region independent of the nozzle-to-plate spacing L/D. In the case of large Reynolds number, heat transfer rate (Nu) was proportional to 0.5 power of the Reynolds number. For L/D=2, a secondary peak in the heat transfer rate was seen in the region of X/D=1.5~3 due to the transition from laminar to turbulent boundary layer.

Measurement of the Local Heat Transfer Coefficient on a Concave Surface with a Turbulent round Impinging Jet (오목표면에 분사되는 난류원형충돌제트에 대한 국소열전달계수 측정에 관한 연구)

  • Lim, K.B.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.7 no.1
    • /
    • pp.112-119
    • /
    • 1995
  • Measurements of the local heat transfer coeffcients on a spherically concave surface with a round impinging jet are presented. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystals for the measurement of the surface temperature. The Reynolds numbers used were 1,000, 23,000 and 50,000 and the nozzle-to-jet distance was L/d=2, 4, 6, 8, 10. Presented results are compared to previous measurements for flat plate. In the experiment, the local heat transfer Nusselt numbers on a concave surface are higher than those on a flat plate. Maximum Nusselt number at all region occured at L/d=6 and second maximum in the Nusselt number occured at R/d=2 for both Re=50,000 and Re=23,000 in case of L/d=2 and for only Re=50,000 in case of L/d=4. All other cases exhibit monotonically decreasing value of the Nusselt number along the curved surface.

  • PDF

The Study on the Phenomenon of Heat Transfer on a Downward Isothermal Circular Surface by an Impinging of Upward Circular Nozzle Jet (상향 원형노즐 제트에 의한 하향 등온 원형평면에서의 열전달 현상에 관한 연구)

  • Lee, In Jae;Eom, Yong Kyoon
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.28 no.11
    • /
    • pp.450-457
    • /
    • 2016
  • While many studies on the heat transfer effect of an impinging jet have been published, most studies focus on the downward impinging jet. This study investigates the impinging jet heat transfer phenomenon when water at a temperature of $24^{\circ}C$ impinges on the downward isothermal circular plate at 60, 70, and $80^{\circ}C$ and when the upward round jet nozzle is 4, 6, and 8 mm diameter with a flow rate 3.6, 4.6, and 5.6 L/min, respectively, and when the ratio of the nozzle clearance/nozzle diameter (H/D) is 1. The results showed that, as the nozzle diameter decreases, the heat transfer coefficient increases at a constant flow rate. The correlation equation of $Nu_r$, $Pr_r$, and $Re_{jg}$ is obtained in the impinging and constant velocity flow region $(Nu_r/Pr^{0.4}_r)Dr=4.6[Re_{jg}(r/R_c)Dr]^{0.8}$ at all flow rates, in the deceleration and falling flow regions $(Nu_r/Pr^{0.4}_r)Dr=42.7{\mid}Re_{jg}(r/R_c)Dr-345.7{\mid}^{0.3}$ at 3.6 L/min, $(Nu_r/Pr^{0.4}_r)Dr=92.4{\mid}Re_{jg}(r/R_c)Dr-16.8{\mid}^{0.2}$ at 4.6 L/min, and $(Nu_r/Pr^{0.4}_r)Dr=322.4{\mid}Re_{jg}(r/R_c)Dr-536.2{\mid}^{0.01}$ at 5.6 L/min.

The characteristics of laminar diffusion flame impinging on the wall (벽면 충돌 층류 확산화염의 특성)

  • Park,Yong-Yeol;Kim, Ho-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.20 no.3
    • /
    • pp.979-987
    • /
    • 1996
  • A theoretical study for the laminar round jet diffusion flame impinging on the wall was carried out to predict the characteristics and structure of impinging jet flame and heat transfer to the wall. Finite chemistry via Arrhenius equation was adopted as the combustion model. All the transport properties were considered as the variable depending on the temperature and composition. For the parametric study, the distance from nozzle to perpendicular wall and Reynolds number at nozzle exit were chosen as the major parameters. As the results of the present study, the characteristics of flow field and the distributions of temperature, density and each chemical species were obtained. The heat transfer rate from flame to the wall and the effective heating area were calculated to investigate the influence of the major parameters on the heat transfer characteristics.

Measurement of the local heat transfer coefficient on a convex hemispherical surface with round oblique impinging jet (볼록한 표면위에 분사되는 원형경사충돌제트의 국소열전달계수 측정에 관한 연구)

  • 최형철;이세균;이상훈;임경빈
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.11 no.6
    • /
    • pp.846-854
    • /
    • 1999
  • Measurements of the local heat transfer coefficients were made on a hemispherically convex surface with a round oblique impinging jet. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystal for the surface temperature measurements. The Reynolds number used was 23000 and the nozzle-to-surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was $\alpha$=$0^{\circ}\; 15^{\circ}\;30^{\circ}C\; and \;40^{\circ}C$. In the experiment, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit Secondary maxima at $0^{\circ}C\re $\alpha$\re 15^{\circ}C, L/d\le6$ for X/d<0(upstream) and at $0^{\circ}C\re $\alpha$40^{\circ}C,\;L/d\le4\;and\; at\; 30^{\circ}C\re $\alpha$$\leq$40^{\circ}C,\;L/d\le 6 $for X/d>0(downstream). The secondary maxima occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. The Y-axis Nusselt number distributions exhibit secondary maxima at Y/d=$\pm$2 for $0^{\circ}C\le a\le30^{\circ}C\; and\; L/d\le4, and \;for\;$\alpha$=40^{\circ}C$and L/d=2. The displacement of the maximum Nusselt number from the stagnation point increases as the jet angle increases or the nozzle-to-surface distance decreases and the maximum distance is about 0.67 times of the nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

  • PDF

Heat Transfer Measurements by a Round Impinging Jet on a Rib-Roughened Flat Plate (표면조도를 가진 평판에서 원형충돌제트에 의한 열전달 측정)

  • Lee, Dae-Hee;Kim, Yun-Taek;Chung, Seung-Hun;Chung, Young-Suk
    • Proceedings of the KSME Conference
    • /
    • 2000.11b
    • /
    • pp.87-92
    • /
    • 2000
  • This study is to investigate the heat transfer characteristics the for a round turbulent jet impinging on the flat plate with and without rib. Liquid crystal/transient method was used to determine the Nusselt number distributions along the surface. The temperature on the surface was measured using liquid crystal and a digital color image processing system. The experiments were made fur the jet Reynolds number (Re) 23,000, the dimensionless nozzle-to-surface distance (L/d) from 2 to 10, and the rib type [height ($d_1$) 2mm, pitch (p) from 12 to 36mm]. It was found that for $L/d{\ge}6$ the average Nusselt numbers on the flat plate with rib type C ($p/d_1=16$) are higher than those without rib, mainly due to an increase in the turbulent intensity caused by flow separation, recirculation and reattachment on the wall surface.

  • PDF