• Title/Summary/Keyword: crossflow

Search Result 176, Processing Time 0.034 seconds

Heat Transfer of Array Impinging Jet on Concave Surfaces with Rectangular Fin (사각 핀이 설치된 오목충돌면에서 배열충돌제트의 국소 열전달 특성 고찰)

  • Oh, Sang-Hyun;Lee, Won-Hee;Lee, Dong-Hyun;Cho, Hyung-Hee;Kim, Mun-Young;Lee, Sung-Ho
    • Proceedings of the SAREK Conference
    • /
    • 2008.06a
    • /
    • pp.1149-1154
    • /
    • 2008
  • The present study investigates the heat transfer characteristics on concave surface with array impinging jet and fin arrangement. The heat transfer coefficients was measured by TLC method. The Reynolds number based on jet hole diameter is 10,000 and hole diameter-to-plate distance ratio (H/d) is fixed at 2. The rectangular fins are installed in the curved channel and the width of fin varies from 1d to 3d. Without fins, the averaged heat transfer coefficients decreases as moves downstream region. While, the rectangular fins block the crossflow and higher heat transfer rates were observed compared to smooth channel.

  • PDF

A Study on the Opimization of Process and Operation Condition for Membrane System in Tap Water Treatment (분리막을 이용한 정수처리 System에서 처리공정 및 운전조건의 최적화에 관한연구)

  • 오중교
    • Membrane Journal
    • /
    • v.9 no.4
    • /
    • pp.193-201
    • /
    • 1999
  • The object of study were the development of membrane process and the optimization of operation condition for membrane system, which was used the pre-treatment system of tap water treatment in steady of conventional process such as coagulation, sedimentation. The higher steady flux is very important factor, by a suitable pre-treatment and optimization of operating condition such as fouling control, crossflow and backwashing method, in membrane system. So, we were observed the effect of flux decline for membrane used by 4 type ultrafiltration(UF) membrane pre-treatment process, and optimized the operation condition of filtration system under various MWCO(Molecular weight cut-off), operation pressure, linear velocity and temperature to maintain higher flux. From these experiment, we were identified that UF process showed a slower flux decline rate and a higher flux recovery than microfiltration(MF) membrane. The water quality of UF permeate was better than that of MF, and was not effected pre-treatment process. In the operation condition, the rate of flux decline was diminished by a higher linear velocity and operation temperature, lower pressure.

  • PDF

ASSESSMENT of CORE BYPASS FLOW IN A PRISMATIC VERY HIGH TEMPERATURE REACTOR BY USING MULTI-BLOCK EXPERIMENT and CFD ANALYSIS (다중블록실험과 전산유체해석을 통한 블록형 초고온가스로의 노심우회유량 평가)

  • Yoon, S.J.;Lee, J.H.;Kim, M.H.;Park, G.C.
    • Journal of computational fluids engineering
    • /
    • v.16 no.3
    • /
    • pp.95-103
    • /
    • 2011
  • In the block type VHTR core, there are inevitable gaps among core blocks for the installation and refueling of the fuel blocks. These gaps are called bypass gap and the bypass flow is defined as a coolant flows through the bypass gap. Distribution of core bypass flow varies according to the reactor operation since the graphite core blocks are deformed by the fast neutron irradiation and thermal expansion. Furthermore, the cross-flow through an interfacial gap between the stacked blocks causes flow mixing between the coolant holes and bypass gap, so that complicated flow distribution occurs in the core. Since the bypass flow affects core thermal margin and reactor efficiency, accurate prediction and evaluation of the core bypass flow are very important. In this regard, experimental and computational studies were carried out to evaluate the core bypass flow distribution. A multi-block experimental apparatus was constructed to measure flow and pressure distribution. Multi-block effect such as cross flow phenomenon was investigated in the experiment. The experimental data were used to validate a CFD model foranalysis of bypass flow characteristics in detail.

An Experimental Study on the Flame Dynamics in the Model Combustor with V-gutter type Flameholder (V-gutter 형 보염기가 장착된 모델 연소기 내에서 발생하는 화염 동특성 연구)

  • Song, Jin-Kwan;Jeong, Chan-Young;Yoon, Young-Bin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2010.11a
    • /
    • pp.379-385
    • /
    • 2010
  • Mechanism of combustion frequencies occurring during combustion is experimentally investigated in a model combustor with V-gutter flameholder. The combustor has a long duct shape with a cross section area of 40×40mm40×40mm. The v-gutter type flameholder with 10, 12, 14mm width is mounted at the side wall of combustor. CNG were used as fuel, and the fuel was injected transversely into air crossflow. It is found that combustion frequencies were considered as first longitudinal mode caused by combustor geometry. And it is found that flameholder length affects the flame holding range. Also, it is observed first longitudinal pressure oscillations make significant changes of flame structure.

  • PDF

Spray Characteristics of Impinging Injectors in Crossflows (횡방향 유동에서 충돌형 분사기의 액체제트 분무 특성)

  • Song, Yoonho;Lee, Woongu;Ahn, Kyubok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2017.05a
    • /
    • pp.949-952
    • /
    • 2017
  • Spray characteristics of the impinging injectors in subsonic crossflows were experimentally studied and compared with the plain-orifice injectors. By changing the impingement angle (60, 90, 120) which is the same orifice length to diameter ratio (L/d = 5), spray characteristics were investigated. In the view of the top view from the impinging injectors, as the impingement angle increases, the liquid column breakup length in the y-direction was decreased. On the other hand, when the impinging injector is viewed from the side view, the breakup length in the x direction is smaller than the previous plain-orifice injectors, which mean that the atomizing performance of the impingement-type injector is better than that of the single-hole orifice.

  • PDF

Progresses and new perspectives of integrated operations for a sustainable industrial growth

  • Drioli, Enrico
    • Proceedings of the Membrane Society of Korea Conference
    • /
    • 1998.10a
    • /
    • pp.11-14
    • /
    • 1998
  • 1. Introduction : Research progresses in Chemistry and Chemical Engineering have been made during the last decades with important contributions to the industrial development and to the quality of our life. An interesting case is related to the membrane science and technology continuous impact to innovative processes and products, particularly appropriate for a sustainable industrial growth. Membrane operations have been familiar for many years to biologists and chemists working in their laboratorier or studying biological phenomena. Only recently engineers started to operate in' this area. The preparation of asymmetric CA membranes at University of California, Los Angeles in the early 60s is generally recognized as a crucial moment for membranology (1). Loeb and Sourirajan with their discovery of how to increase significantly the permeability of polymeric membranes without significant changes in their selectivity, made realistic the possibility of their use in large scale operations for desalting brackish and sea water by reverse osmosis and for various other molecular separations in different industrial areas. Reverse osmosis is today a well recognized basic unit operations, togheter with ultrafiltration, crossflow microfiltration,. nanofiltration, all pressure driven membrane processes. Already in 1992 more than 4 milIions m33/day were the total capacity of RO desalination plants and in 1995 more than 180.000 m22 of ultrafiltration membranes were installed for the treatment of wheys and milk (2) (3).

  • PDF

Application of a Membrane Bioreactor in Denitrification of Explosives Hydrolysates (Membrane Bioreactor를 이용한 폭발성 물질의 가수분해 부산물의 탈질과정에의 적용)

  • Zoh, Kyung-Duk
    • Journal of Korean Society on Water Environment
    • /
    • v.18 no.2
    • /
    • pp.113-122
    • /
    • 2002
  • A bench-scale anoxic membrane bioreactor (MBR) system, consisting of a bioreactor coupled to a ceramic crossflow ultrafiltration module, was evaluated to treat a synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX, The wastewater was formulated the same as RDX hydrolysates, and consisted of acetate, formate, formaldehyde as carbon sources and nitrite, nitrate as electron accepters. The MBR system removed 80 to 90% of these carbon sources, and approximately 90% of the stoichiometric amount of nitrate, 60% of nitrite. The reactor was also operated over a range of transmembrane pressures, temperatures, suspended solids concentration, and organic loading rate in order to maximize treatment efficiency and permeate flux. Increasing transmembrane pressure and temperature did not improve membrane flux significantly. Increasing biomass concentration in the bioreactor decreased the permeate flux significantly. The maximum volumetric organic loading rate was 0.72kgCOD/m3/day0.72kgCOD/m3/day, and the maximum F/M ratio was 0.50 kg N/kg MLSS/day and 1.82 kg COD/kg MLSS/day. Membrane permeate was clear and essentially free of bacteria, as indicated by heterotrophic plate count. Permeate flux ranged between 0.15 and 2.0m3/m2/day2.0m3/m2/day and was maintained by routine backwashing every 3 to 4 day. Backwashing with 2% NaOCl solution every fourth or fifth backwashing cycle was able to restore membrane flux to its original value.

The Review of Studies on Heat Transfer in Impinging Jet

  • Hong, Sung-Kook;Cho, Hyung-Hee
    • International Journal of Air-Conditioning and Refrigeration
    • /
    • v.13 no.4
    • /
    • pp.196-205
    • /
    • 2005
  • In this paper, recent research trend on heat transfer in impinging jet is reviewed. We focused on submerged jet that air issued into air or liquid issued into liquid. To control and enhance the heat transfer in single jet, researchers have performed a lot of experiments by considering the nozzle geometry, impinging surface and active method such as jet vibration, secondary injection and suction flow. The studies on multiple jet have been mainly focused on finding out the optimum condition and on investigating many different factors concerned with application condition (crossflow, rotation and geometry etc.) and combined techniques (rib turbulator, pin fin, dimple and effusion hole etc.). All most experiments showed the detailed heat transfer data by using liquid crystal method, infrared camera technique and naphthalene sublimation method. Many numerical calculations have been performed to investigate the flow and heat transfer characteristics in laminar jet region. Various turbulence models such as kε¯ν2kε¯ν2, modified kεfμkεfμ were applied to the calculation for turbulent jet and the predicted results showed a good agreement with the experimental data. Although a lot of studies on impinging jet have performed consistently up to recently, further studies are still required to understand the flow and heat transfer characteristics more accurately, and to give a guideline for optimum impinging jet design in various applications.

Experimental characterization of the lateral and near-wake flow for the BARC configuration

  • Pasqualetto, Elena;Lunghi, Gianmarco;Rocchio, Benedetto;Mariotti, Alessandro;Salvetti, Maria Vittoria
    • Wind and Structures
    • /
    • v.34 no.1
    • /
    • pp.101-113
    • /
    • 2022
  • We experimentally investigate the high-Reynolds flow around a rectangular cylinder of aspect ratio 5:1. This configuration is the object of the international BARC benchmark. Wind tunnel tests have been carried out for the flow at zero angle of attack and a Reynolds number, based on the crossflow cylinder length and on the freestream velocity, equal, to 40 000. Velocity measurements are obtained by using hot-wire anemometry along 50 different cross-flow traverses on the cylinder side and in the near wake. Differential pressure measurements are acquired on multiple streamwise sections of the model. The obtained measurements are in a good agreement with the state-of-the-art experiments. For the first time among the several contributions to the BARC benchmark, detailed flow measurements are acquired in the region near the cylinder side and in the near-wake flow. The edges and the thickness of the shear layers detaching from the upstream edges are derived from velocity measurements. Furthermore, we compute the flow frequencies characterizing the roll-up of the shear layers, the evolution of vortical structures near the cylinder side and the vortex shedding in the wake.

Degradation analysis of horizontal steam generator tube bundles through crack growth due to two-phase flow induced vibration

  • Amir Hossein Kamalinia;Ataollah Rabiee
    • Nuclear Engineering and Technology
    • /
    • v.55 no.12
    • /
    • pp.4561-4569
    • /
    • 2023
  • A correct understanding of vibration-based degradation is crucial from the standpoint of maintenance for Steam Generators (SG) as crucial mechanical equipment in nuclear power plants. This study has established a novel approach to developing a model for investigating tube bundle degradation according to crack growth caused by two-phase Flow-Induced Vibration (FIV). An important step in the approach is to calculate the two-phase flow field parameters between the SG tube bundles in various zones using the porous media model to determine the velocity and vapor volume fraction. Afterward, to determine the vibration properties of the tube bundles, the Fluid-Solid Interaction (FSI) analysis is performed in eighteen thermal-hydraulic zones. Tube bundle degradation based on crack growth using the sixteen most probable initial cracks and within each SG thermal-hydraulic zone is performed to calculate useful lifetime. Large Eddy Simulation (LES) model, Paris law, and Wiener process model are considered to model the turbulent crossflow around the tube bundles, simulation of elliptical crack growth due to the vibration characteristics, and estimation of SG tube bundles degradation, respectively. The analysis shows that the tube deforms most noticeably in the zone with the highest velocity. As a result, cracks propagate more quickly in the tube with a higher height. In all simulations based on different initial crack sizes, it was observed that zone 16 experiences the greatest deformation and, subsequently, the fastest degradation, with a velocity and vapor volume fraction of 0.5 m/s and 0.4, respectively.