Experimental Study on Fluid Mixing for Evaluation of Thermal Striping in T-Pipe Junction

2002 ◽  
Author(s):  
Minoru Igarashi ◽  
Masaaki Tanaka ◽  
Shigeyo Kawashima ◽  
Hideki Kamide
Keyword(s):  
Temperature Fluctuation ◽  
Velocity Ratio ◽  
Impinging Jet ◽  
Fluid Mixing ◽  
Cold Spot ◽  
Wall Jet ◽  
Fluid Temperature ◽  
Thermochromic Liquid Crystal ◽  
Inflow Condition ◽  
Thermal Striping

A water experiment is performed to investigate thermal striping phenomena in a T-pipe junction which is a typical geometry of fluid mixing. The flow velocity ratio and temperature difference were experimental parameters. The jet form was classified into four patterns; (1) impinging jet, (2) deflecting jet, (3) re-attachment jet and (4) wall jet according to the inflow condition. The parameter experiments showed that the jet form could be predicted by a momentum ratio between the two pipes. The thermochromic liquid crystal sheet showed that a cold spot was formed at the wall surface in the main pipe in the cases of the impinging jet and the wall jet. From the temperature measurement in the fluid, temperature fluctuation intensity was high along the edge of the jet exiting from branch piping. A database of temperature fluctuation and frequency characteristics was established for an evaluation rule of thermal striping in a T-pipe junction.

Stress Response Functions to Multi-Dimensional Spatial Fluctuations of Fluid Temperature

2002 ◽  
Author(s):  
Naoto Kasahara ◽  
Hideki Takasho
Keyword(s):  
Thermal Stress ◽  
Temperature Fluctuation ◽  
Thermal Stratification ◽  
Thermal Stresses ◽  
Fluid Mixing ◽  
Cold Spot ◽  
Fluid Temperature ◽  
Response Functions ◽  
Spatial Fluctuations ◽  
Stress Functions

Temperature fluctuation from incomplete fluid mixing induces fatigue damages on structures of nuclear components, which should be prevented. For rational analyses of this phenomenon, the authors have developed a frequency response function of thermal stress and extended to multi-dimensional spatial fluctuations of fluid temperature. This function is formulated by a product of the effective heat transfer and the effective thermal stress functions, and enables us to quickly calculate the thermal stresses induced by both local and global temperature distributions in structures. Furthermore, it can evaluate sensitivities of thermal stress to frequencies of temperature fluctuation, Biot number and constraint conditions of structures. Applicability of this function was verified for multi-dimensional problems such as thermal stratification problems and hot/cold spot ones.

Numerical Investigations of Arched Vortex Characteristics Generated at T-Junction Piping Systems

2004 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Stokes Equations ◽  
Velocity Ratio ◽  
Navier Stokes ◽  
Fluid Temperature ◽  
Simulation Code ◽  
Navier Stokes Equations ◽  
Downstream Region ◽  
Piping Systems ◽  
Frequency Components ◽  
Thermal Striping

Thermohydraulic analyses for a fundamental water experiment simulating thermal striping phenomena at T-junction piping systems were carried out using a quasi-direct numerical simulation code DINUS-3, which is represented by instantaneous Navier-Stokes equations and deals with a modified third-order upwind scheme for convection terms. Calculated results were compared with experimental results on the flow patterns in the downstream region of the systems, the arched vortex structures under a deflecting jet condition, the generation frequency of the arched vortex, etc. in the various conditions; i.e., diameter ratio α, flow velocity ratio β and Reynolds number Re. From the comparisons, it was confirmed that (1) the DINUS-3 code is applicable to the flow pattern classifications in the downstream region of the T-junction piping systems, (2) the arched vortex characteristics with lower frequency components and their generation possibilities can be estimated numerically by the DINUS-3 code, and (3) special attentions should be paid to the arched vortex generations with lower frequency components of fluid temperature fluctuations in the design of T-junction systems from the viewpoints of the avoidances for the thermal striping.

scholarly journals Studies on the Flow of Axisymmetric Radialwise Wall Jet on the Impinged Wall by the Annular Impinging Jet

1980 ◽  
Vol 23 (176) ◽  
pp. 217-223 ◽  
Author(s):  
Hiroshi MAKI ◽  
Hikoaki ITO ◽  
Fumitaka SAIGO
Keyword(s):  
Impinging Jet ◽  
Wall Jet

Application of the Transient Heat Transfer Measurement Technique Using TLC in a Network Configuration With Intersecting Circular Passages

2018 ◽  
Author(s):  
Anika Steurer ◽  
Rico Poser ◽  
Jens von Wolfersdorf ◽  
Stefan Retzko
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Mass Flow ◽  
Fluid Temperature ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Flow Rates ◽  
Flow Network ◽  
Mass Flow Rates ◽  
Time Information

The present study deals with the application of the transient thermochromic liquid crystal (TLC) technique in a flow network of intersecting circular passages as a potential internal turbine component cooling geometry. The investigated network consists of six circular passages with a diameter d = 20mm that intersect coplanar at an angle θ = 40°, the innermost in three, the outermost in one intersection level. Two additional non-intersecting passages serve as references. Such a flow network entails specific characteristics associated with the transient TLC method that have to be accounted for in the evaluation process: the strongly curved surfaces, the mixing and mass flow redistribution at each intersection point, and the resulting gradients between the wall and passage centerline temperatures. All this impedes the choice of a representative fluid reference temperature, which results in deviations using established evaluation methods. An alternative evaluation approach is introduced, which is supported by computational results obtained from steady-state three-dimensional RANS simulations using the SST turbulence model. The presented analysis uncouples local heat transfer coefficients from actually measured local temperatures but uses the time information of the thermocouples instead that represents the fluid temperature step change and evolution along the passages. This experimental time information is transferred to the steady-state numerical bulk temperatures, which are finally used as local references to evaluate the transient TLC experiments. As effective local mass flow rates in the passage sections are considered, the approach eventually allows for a conclusion whether heat transfer is locally enhanced due to higher mass flow rates or the intersection effects.

scholarly journals Study on Mechanism of Series-Flow of Pollutants between Consecutive Tunnels by Numerical Simulation

2019 ◽  
Vol 9 (19) ◽  
pp. 4125
Author(s):  
Honghu Zhang ◽  
Yunge Hou ◽  
Kaijie Wu ◽  
Tianhang Zhang ◽  
Ke Wu ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Wall Jet ◽  
Air Velocity ◽  
Pressure Area ◽  
Computational Fluid Dynamics Cfd ◽  
Jet Theory ◽  
Jet Characteristics ◽  
Tunnel Entrance

The characteristics of series-flow between two consecutive tunnels with distance ranging from 20 m to 250 m are explored by computational fluid dynamics (CFD) parametric simulations of structure and operation parameters. The research indicates that series-flow can be considered the three-dimensional wall jet diffusion of upstream tunnel pollutants under the effects of the negative pressure area of the downstream tunnel entrance. The jet characteristics are primarily related to the tunnel distance between upstream and downstream tunnels and hydraulic diameters, and only influenced by the negative pressure in the area very close to downstream entrance where the tunnel air velocity ratio, i.e., the velocity of upstream tunnel air divided by the velocity of downstream tunnel air, decides the degree of the influence. If ignoring the effects of ambient wind and traffic flow, the series-flow ratio decreases with the increasing of parameters of the normalized tunnel distance, i.e., the tunnel distance divided by tunnel hydraulic diameter, and the tunnel air velocity ratio. Based on the three-dimensional wall jet theory, a series-flow model covering all jet characteristic sections is built. The experiment results indicate that the model applies to consecutive tunnels with any spacing and exhibits higher prediction accuracy.

Performance analysis of different turbulence models in impinging jet cooling

2020 ◽  
Vol 31 (04) ◽  
pp. 2050051
Author(s):  
Shashikant Pawar ◽  
Devendra Kumar Patel
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Transfer Problem ◽  
Impinging Jet ◽  
Experimental Results ◽  
Wall Jet ◽  
Quadratic Formula ◽  
Upward Direction ◽  
Number Formula ◽  
Text Model

The characteristics of heat transfer from a hot wall surface for the oblique impingement of a free turbulent slot jet have been investigated numerically. Different turbulent models — the [Formula: see text]-[Formula: see text], [Formula: see text]-[Formula: see text], SST [Formula: see text]-[Formula: see text], cubic [Formula: see text]-[Formula: see text] and quadratic [Formula: see text]-[Formula: see text] models — are used for the prediction of heat transfer and their results were compared with experimental results reported in the literature. The comparison shows that the [Formula: see text]-[Formula: see text], quadratic [Formula: see text]-[Formula: see text] and SST [Formula: see text]-[Formula: see text] models give more unsatisfactory results for the investigated configuration, while the cubic [Formula: see text]-[Formula: see text] model is capable of predicting the local Nusselt number in wall-jet region only. The [Formula: see text]-[Formula: see text] model exhibits the best agreement with the experimental results in both stagnation and wall-jet regions. Further, the [Formula: see text]-[Formula: see text] model is applied to analyze the obliquely impinging jet heat transfer problem. The parametric effects of the jet inclination ([Formula: see text], [Formula: see text] and [Formula: see text]), jet-to-surface distance ([Formula: see text], 6 and 8), Reynolds number ([Formula: see text], 15[Formula: see text]000 and 20[Formula: see text]000), and turbulent intensity ([Formula: see text], [Formula: see text] and [Formula: see text]) have been presented. The heat transfer on the upward direction is seen to decrease, while that on the downward direction it rises for the increasing angle. It is to be noted that as the value of [Formula: see text] decreases, the point of maximum Nusselt number ([Formula: see text]) displaces toward the upward direction from the geometric center point as well as its value reduces. The shifting of the [Formula: see text] is found to be independent of Re and [Formula: see text] within the range considered for the study.

Numerical Investigations of a Turbulence Mixing Process Related to Thermal Striping Phenomena at a T-Junction of Liquid Metal Fast Reactor Piping Systems

2002 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Liquid Metal ◽  
Fast Reactor ◽  
Evaluation System ◽  
Velocity Ratio ◽  
Piping System ◽  
Mixing Process ◽  
Downstream Region ◽  
Piping Systems ◽  
Turbulence Mixing ◽  
Thermal Striping

Fluid-structure thermal interaction phenomena characterized by stationary random temperature fluctuations, namely thermal striping are observed in the downstream region of a T-junction piping system of liquid metal fast reactor (LMFR). Therefore the piping walls located in the downstream region must be protected against the stationary random thermal process which might induced high-cycle fatigue. This paper describes the evaluation system based on numerical simulation methods for the thermal striping, and numerical results of the thermal striping at a T-junction piping system under the various parameters, i.e., velocity ratio and diameter ratio between both the pipes and Reynolds number. Then detailed turbulence mixing process at the T-junction piping region due to arched vortexes generating lower frequency fluctuations are evaluated through a separate numerical analysis of a fundamental water experiment.

Numerical Simulation of Thermal Striping Phenomena in T-Junction Piping System Using Large Eddy Simulation

2008 ◽  
Author(s):  
Masa-Aki Tanaka ◽  
Hiroyuki Ohshima ◽  
Hideaki Monji
Keyword(s):  
Numerical Simulation ◽  
Heat Conduction ◽  
Three Dimensional ◽  
Piping System ◽  
Fluid Temperature ◽  
Numerical Schemes ◽  
Simulation Code ◽  
Simple Method ◽  
Thermal Striping ◽  
Les Model

In Japan Atomic Energy Agency (JAEA), simulation code “MUGTHES (MUlti Geometry simulation code for THErmal-hydraulic and Structure heat conduction analysis in boundary fitted coordinate)” has been developed to evaluate thermal striping phenomena that are caused by turbulence mixing of fluids in different temperature. MUGTHES employs Boundary Fitted Coordinate (BFC) system to treat complex geometries in power plants. And MUGTHES can deal with three-dimensional transient thermal-hydraulic problem coupled with three-dimensional transient heat conduction in the surrounding structure in consideration of conjugated heat transfer. In this paper, numerical schemes for thermal-hydraulic simulation employed in MUGTHES are described including LES model. A simple method to limit numerical oscillation is adopted in energy equation solving process. A new iterative method to solve Poisson equation in BFC system is developed for effective transient calculations. This method is based on BiCGSTAB method and SOR technique. As the code validation of MUGTHES, a numerical simulation in a T-junction piping system with LES approach was conducted. Numerical results related to velocity and fluid temperature distributions were compared with an existing water experimental data and the applicability of numerical schemes with LES model in MUGTHES to the thermal striping phenomenon was confirmed.

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