Numerical Investigation of a Heated Sodium Jet in a Co-Flow

2007 ◽  
Author(s):  
I. Otic´ ◽  
A. G. Class
Keyword(s):  
Heat Transfer ◽  
Pipe Wall ◽  
Experimental Studies ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Velocity ◽  
Temperature Variance ◽  
Physical Mechanisms ◽  
Insight Into ◽  
Good Agreement

Results of a numerical simulation of turbulent heated sodium jet in a co-flow using a combined LES-DNS approach are presented. The calculations correspond to the experiment of Knebel, Krebs, Muller and Axcell [1]. In agreement with the experimental results co-flow suppresses flow reversal along the outlet pipe wall. Comparisons of mean velocity, mean temperature, and temperature variance between experimental and numerical results show fairly good agreement. The results support the applicability of the combined LES-DNS approach for this type of flows. Simulations using this approach may complement experimental studies, allowing for better insight into the physical mechanisms of liquid metal turbulent heat transfer.

Numerical Simulations on Turbulent Heat Transfer Characteristics of Supercritical Pressure Fluids

2009 ◽  
Author(s):  
Toru Nakatsuka ◽  
Kazuyuki Takase ◽  
Hiroyuki Yoshida ◽  
Takeharu Misawa
Keyword(s):  
Heat Transfer ◽  
Prediction Accuracy ◽  
Experimental Studies ◽  
Supercritical Pressure ◽  
Turbulent Heat Transfer ◽  
High Heat Flux ◽  
Turbulent Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Annular Channels

As one of next generation nuclear reactors, development of a supercritical pressure water reactor (SCWR) has been performed. In order to design the SCWR, it is necessary to investigate thermal-hydraulic characteristics in the SCWR core precisely. As for those characteristics, many experimental studies have been conducted from the former in each country using circular tubes, annular channels, and the simulated fuel bundles. An objective of this study is to clarify the prediction accuracy of the turbulent heat transfer characteristics in the supercritical pressure fluids for the SCWR design. From the experimental results of the supercritical pressure fluids flowing upward in a vertical circular tube, it was confirmed that the turbulent heat transfer coefficient suddenly decreases under the high heat flux condition. Although many numerical studies have been done in order to confirm the deterioration of turbulent heat transfer in supercritical pressure fluids, it is important to choose a suitable turbulence model to obtain high prediction accuracy. Then, the present study was performed to investigate numerically the effect of turbulent models on the deteriorated turbulent heat transfer.

Modified Algebraical Cebeci --- Smith Turbulent Viscosity Model for the Entire Surface of a Blunted Cone

2020 ◽  
pp. 28-41
Author(s):  
V.V. Gorskiy ◽  
A.G. Loktionova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Experimental Studies ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Entire Surface ◽  
Wide Range ◽  
Semi Empirical ◽  
Transfer Properties ◽  
Turbulent Pulsations

In order to compute the intensity of laminar-turbulent heat transfer, algebraic or differential models are commonly used, which are designed to compute the contribution of turbulent pulsations to the transfer properties of the gas. This, in turn, dictates the necessity of validating these semi-empirical models against experimental data obtained under conditions simulating the gas dynamics inherent to the phenomenon as observed in practice. The gas dynamic patterns observed during gradient flow around fragments of aircraft structure (such as a sphere or a cylinder) differs qualitatively from the patterns revealed by the flow around the lateral surfaces of these fragments, which necessitates using various semi-empirical approaches in this case, followed by mandatory validation against the results of respective experimental studies. In recent years, there appeared scientific publications dealing with modifying one of the algebraic models designed to compute the contribution of turbulent pulsations in the boundary layer to the transfer properties of the gas; this was accomplished by making use of experimental data obtained for a hemisphere at extremely high Reynolds numbers. The paper proposes a similar modification of the same turbulence model, based on fitting a wide range of experimental data obtained for lateral surfaces of spherically blunted cones. As a result of the investigations conducted, we stated a method for computing laminar-to-turbulent heat transfer over the entire surface of a blunted cone; the accuracy of the method is acceptable in terms of most practical applications. We show that the computational method presented is characterised by minimum error as compared to the most widely spread methods for solving this problem

Simulation of Circular Tubes Fitted with V Cut and Square Cut Rotors

2013 ◽  
Vol 561 ◽  
pp. 547-552
Author(s):  
Peng Jiang ◽  
Hua Yan ◽  
Zhen Zhang ◽  
Yu Mei Ding ◽  
Wei Min Yang
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Turbulent Heat Transfer ◽  
Cfd Modeling ◽  
Turbulent Heat ◽  
Circular Tubes ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

This work presents the effect of V cut and square cut rotors in circular tubes for turbulent heat transfer using computational fluid dynamics (CFD) modeling. The computational results are in good agreement with experimental data. The obtained results reveal that the use of square cut rotors leads to higher Nusselt number than use of V cut rotors. The results also show that the heat transfer rate, friction factor and thermal performance factor of rotors with square cut increase with the increase of width (a) and depth (b) of rotors’ cut. Square cut rotors with a=b=3 yields higher mean thermal performance factor than those with other width and depth, a=b=1, 2 and the highest thermal performance factor of square cut rotors at a=b=1, 2, 3 are found to be 2.08, 2.11 and 2.13.

STEADY STATE HEAT TRANSFER TO FULLY DEVELOPED TURBULENT FLOW IN A CURVED CHANNEL

1957 ◽  
Vol 35 (4) ◽  
pp. 410-434
Author(s):  
A. W. Marris
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Flow ◽  
Curved Channel ◽  
Mean Velocity ◽  
Fully Developed Turbulent Flow ◽  
Angular Velocities ◽  
The Mean

A vorticity transfer analogy theory of turbulent heat transfer is developed first for the case of fully developed turbulent flow under zero transverse pressure and temperature gradients such as that in the annulus between concentric cylinders rotating with different angular velocities or in a "free vortex". The mean flow is assumed to be two-dimensional. The theory, which requires that the turbulence be statistically isotropic, yields a temperature distribution in agreement with experiment except in narrow regions immediately adjacent to the boundaries. An argument is given to show that the boundary layer thickness should be of the order of the reciprocal of the square root of the mean velocity, these boundaries are introduced, and Nusselt moduli are defined and their dependence on Reynolds and Prandtl numbers is investigated.The temperature distributions for the case of non-zero transverse temperature and pressure gradients, i.e. for the case of flow in a curved channel in which the fluid does not flow back into itself, are then obtained and the applicability of the simpler equations for zero transverse gradients to this case is investigated.

Numerical and Experimental Studies of Turbulent Heat Transfer in Inclined Pin-Fin Channels With a Wavy Endwall

2010 ◽  
Author(s):  
Yutaka Oda ◽  
Kenichiro Takeishi ◽  
Yoshiaki Miyake ◽  
Hideki Moriai ◽  
Yusuke Motoda
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Experimental Studies ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Pin Fin ◽  
Naphthalene Sublimation Technique ◽  
Large Eddy ◽  
Naphthalene Sublimation ◽  
The Hill

Endwall heat transfer characteristics of inclined pin-fin channels have been investigated to improve the cooling efficiency of gas turbine’s combustor liners. The time-mean local Nusselt number profiles were obtained in high spatial resolution by naphthalene sublimation technique based on the heat/mass transfer analogy and large eddy simulations. Inclined pin-fin channels with a flat or wavy endwall were tested and compared with each other. As a result, the time-averaged heat transfer coefficient of the wavy endwall was found to be higher than that of the flat endwall due to flow separation and reattachment from the hill of wavy endwall. Surprisingly, the wavy endwall case shows less or at least the same pressure loss compared to the flat endwall case. Therefore, it can be concluded that wavy endwalls can realize better heat transfer with less pressure loss as long as the aim consists in enhancing the endwall heat transfer in inclined pin-fin channels.

Hybrid RANS-LES Simulation of Turbulent Heat Transfer in a Channel Flow With Imposed Spanwise and Streamwise Mean Temperature Gradient

2019 ◽  
Author(s):  
Olalekan O. Shobayo ◽  
D. Keith Walters
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Channel Flow ◽  
Plane Channel ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Mean Temperature ◽  
The Mean

Abstract Computational fluid dynamics (CFD) results for turbulent flow and heat transfer in a plane channel are presented. This study presents an idealized fully-developed planar channel flow case for which the mean velocity gradient is non-zero only in the wall-normal direction, and the mean temperature gradient is imposed to be uniform and non-zero in the streamwise or spanwise direction. Previous studies have documented direct numerical simulation results for periodic channel flow with mean temperature gradient in both the streamwise and wall-normal directions, but limited investigations exist documenting the effect of imposed spanwise gradient. The objective of this study is to evaluate turbulent heat flux predictions for three different classes of modeling approach: Reynolds-averaged Navier-Stokes (RANS), large-eddy simulation (LES), and hybrid RANS-LES. Results are compared to available DNS data at Prandtl number of 0.71 and Reynolds number of 180 based on friction velocity and channel half-width. Specific models evaluated include the k-ω SST RANS model, monotonically integrated LES (MILES), improved delayed detached eddy simulation (IDDES), and dynamic hybrid RANS-LES (DHRL). The DHRL model includes both the standard formulation that has been previously documented in the literature as well as a modified version developed specifically to improve predictive capability for flows in which the primary mean velocity and mean temperature gradients are not closely aligned. The modification consists of using separate RANS-to-LES blending parameters in the momentum and energy equations. Results are interrogated to evaluate the performance of the three different model types and specifically to evaluate the performance of the new modified DHRL variant compared with the baseline version.

Turbulent Heat Transfer Over a Moving Plate Due to Impinging Slot Jets

2010 ◽  
Author(s):  
Himadri Chattopadhyay ◽  
Ali Cemal Benim
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Vertical Direction ◽  
Surface Velocity ◽  
Plate Motion ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Velocity ◽  
Surface Motion ◽  
Surface Movement

In the present paper, turbulent heat transfer characteristics of slot jets impinging on a moving surface up to a Reynolds number of 50,000 have been studied. The turbulent flow field was resolved using the realizable k-ε model due to Shi et al. (1995) after rigorously establishing the adequacy of the model by comparison with large-eddy simulation data. A periodic element from a jet-bank configuration was chosen in the direction of the surface movement. The distribution of heat transfer on impinging surface is found to be significantly affected by the plate motion. However, the mean velocity distribution along vertical direction in the stagnation region is not affected by the plate motion. With increasing surface motion, the initial symmetric distribution changes to an inclined-S type pattern in the direction of the surface movement up to a certain level of surface velocity and the average heat transfer reduces. When the surface motion crosses this level, the net heat transfer starts increasing. The amount of heat transfer was found to be linked with the level of turbulent kinetic energy near the impingement region. The surface velocity at which the heat transfer reaches the value corresponding to the fixed surface value increases with increasing Reynolds number.

scholarly journals Modeling and Simulations of Deteriorated Turbulent Heat Transfer in Wall Heated Cylindrical Tube

2019 ◽  
Author(s):  
Prasad Vegendla ◽  
Rui Hu
Keyword(s):  
Heat Transfer ◽  
Nuclear Power ◽  
Cylindrical Tube ◽  
Fluid Flows ◽  
Turbulent Heat Transfer ◽  
Wall Region ◽  
Turbulent Heat ◽  
Modeling And Simulations ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Abstract The paper discusses the modeling and simulations of Deteriorated Turbulent Heat Transfer (DTHT) for a wall-heated fluid flows, which can be observed in gas-cooled nuclear power reactors during Pressurized Conduction Cooldown (PCC) event due to loss of force circulation flow. The DTHT regime is defined as the deterioration of normal turbulent heat transport due to increase of acceleration and buoyancy forces. The Computational Fluid Dynamics (CFD) tools such as Nek5000 and STAR-CCM+ can help to analyze the DTHT phenomena in reactors for efficient thermal-fluid designs. 3D CFD non-isothermal modeling and simulations were performed in a wall-heated circular tube. The simulation results were verified with two different CFD tools, Nek5000 and STAR-CCM+, and validated with an experimental data. The predicted bulk temperatures were identical in both CFD tools, as expected. Good agreement between simulated results and measured data were obtained for wall temperatures along the tube axis using Nek5000. In STAR-CCM+, the under-predicted wall temperatures were mainly due to higher turbulence in the wall region. In STAR-CCM+, the predicted DTHT was over 48% at outlet when compared to inlet heat transfer values.

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