Swirl Flow Investigations on the Enhancement of Heat Transfer Processes in Cyclone Cooling Ducts

2012 ◽  
Author(s):  
Florian Wassermann ◽  
Sven Grundmann ◽  
Michael Kloss ◽  
Heinz-Peter Schiffer
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Complex Structure ◽  
Three Dimensional ◽  
Swirl Flow ◽  
Flow Structures ◽  
Stable Complex ◽  
Reynolds Analogy ◽  
Transfer Processes ◽  
Cooling Ducts

Cyclone cooling is a promising method to enhance heat-transfer processes in future internal turbine-blade leading-edge cooling-ducts. The basic component of such cooling channels is the swirl generator, which induces a swirling movement of the coolant. The angular momentum generates stable, complex and three-dimensional flow structures of helical shape with alternating axial flow directions. Full three-dimensional and three-component velocity measurements using magnetic resonance velocimetry (3D3C-MRV) were conducted, with the aim to understand the complex structure of pipe flows with strong swirl. In order to mimic the effect of different installation concepts of the cyclone-cooling ducts an idealized bend-duct swirl-tube configuration with variable exit orifices has been investigated. Pronounced helical flow structures and distinct velocity zones could be found in this swirl flow. One substantial result is the identification of stationary helix-shaped streaks of high axial velocity in the direct vicinity of the wall. These findings are in good agreement with mass-transfer measurements that also show helix-shaped structures with increased mass transfer at the inner surface of the tube. According to the Reynolds analogy between heat and mass transfer, augmented heat-transfer processes in these areas are to be expected.

Local Heat Transfer Characteristics in Simulated Electronic Modules

2003 ◽  
Vol 125 (3) ◽  
pp. 362-368 ◽  
Author(s):  
Seong-Yeon Yoo ◽  
Jong-Hark Park ◽  
Min-Ho Chung
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Dimensional Array ◽  
Transfer Characteristics

When heat is released by forced convection from electronic modules in a narrow printed circuit board channel, complex flow phenomena—such as stagnation and acceleration on the front surface, separation and reattachment on the top surface, wake or cavity flow near the rear surface—affect the heat transfer characteristics. The purpose of this study is to investigate how these flow conditions influence the local heat transfer from electronic modules. Experiments are performed on a three-dimensional array of hexahedral elements as well as on a two-dimensional array of rectangular elements. Naphthalene sublimation technique is employed to measure three-dimensional local mass transfer, and the mass transfer data are converted to their counterparts of the heat transfer process using the analogy equation between heat and mass transfer. Module location and streamwise module spacing are varied, and the effect of vortex generators on heat transfer enhancement is also examined. Dramatic change of local heat transfer coefficients is found on each surface of the module, and three-dimensional modules have a little higher heat transfer value than two-dimensional modules because of bypass flow. Longitudinal vortices formed by vortex generator enhance the mixing of fluids and thereby heat transfer, and the rectangular wing type vortex generator is found to be more effective than the delta wing type vortex generator.

Research Needs: Industrial Spray Processes, Spray Drying, and Heat Transfer

1988 ◽  
Vol 41 (10) ◽  
pp. 365-370 ◽  
Author(s):  
William S. Janna
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
High Pressure ◽  
Spray Drying ◽  
Research Needs ◽  
Comprehensive Model ◽  
Research Topics ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Enhance Mass

A survey of researchers and of manufacturers of spraying, drying, and spray heat transfer equipment was conducted. Those that responded provided descriptions of processes and devices that need developmental attention. Several of these problems are described here (eg, a unifying theory of how atomization takes place; a method of evaluating the performance of a spray used to dissolve air in water to enhance mass transfer processes; a comprehensive model for predicting heat transfer from high pressure sprays; etc). It is concluded that many research topics can be gleaned from industry as needs develop and innovative ways are found for sprays to replace conventional methods.

Very-Large Eddy Simulations of Disk Heat Transfer in a Rotating Cavity Using Lattice-Boltzmann Method

2018 ◽  
Author(s):  
J. Kouwa ◽  
Y. Iso ◽  
F. Polidoro ◽  
S. Gautier
Keyword(s):  
Heat Transfer ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Three Dimensional ◽  
Flow Structures ◽  
Physical Parameters ◽  
Transfer Coefficients ◽  
Experimental Heat ◽  
Large Eddy ◽  
Boltzmann Method

Convective heat transfer in the cavity between two corotating disks is of great importance for turbomachinery applications. The complex three dimensional and unsteady flow structures induced by the Coriolis forces inside the cavity, and therefore the resulting heat transfer, are challenging to be measured in an experiment or predicted by simulation. In this paper a simplified cavity geometry, characterized experimentally by Long at al., has been chosen. The results obtained with a Very Large Eddy Simulation using Lattice-Boltzmann Method for two operating point with different rotation speeds are compared to the experimental heat transfer coefficients at the wall. The simulation results show the characteristic flow structures and behavior induced by the different regimes. A sensitivity analysis of the results is presented, both for numerical parameters such as grid resolution and for physical parameters, namely the throughflow velocity profile and shroud temperature.

Heat and Mass Transfer Processes and the Performance Evaluation in Single-Slope Solar Stills

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
David A. Aderibigbe
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat And Mass Transfer ◽  
Glass Cover ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Basin Water ◽  
The Heat Transfer Coefficient

The paper reviews the present understanding of the analysis of the heat and mass transfer processes in single-slope solar stills. By using the results of published experiments, it is proposed that the heat and mass transfer phenomena from the basin water to the glass cover are coupled. This coupling makes it possible to derive the dependence of the heat transfer coefficient for condensation on the inclination of the glass cover of the still. The derived relation, i.e., Nucon = 0.738 (Grcon*Prcon*sin β/Ja*)¼ A−1 where A is the aspect ratio, has been demonstrated to be an important expression for predicting the heat transfer coefficient for condensation hcon necessary for a more realistic evaluation of the overall efficiency of single-slope solar still of a given cover angle β.

scholarly journals TWO-PHASE MODELLING OF THERMAL DISSIPATION IN A NATURAL BASIN

2004 ◽  
Vol 12 (3) ◽  
pp. 103-107 ◽  
Author(s):  
Pranas Baltrenas ◽  
Petras Vaitiekūnas ◽  
Vladislovas Katinas ◽  
Antanas Markevičius
Keyword(s):  
Heat Transfer ◽  
Wind Velocity ◽  
Three Dimensional ◽  
Viscosity Coefficient ◽  
Thermal Dissipation ◽  
Stream Velocity ◽  
Mixing Rate ◽  
Two Phase ◽  
Transfer Processes ◽  
The Mean

The state of two‐phase flow ‘liquid‐gas’ has been modeled numerically by the three‐dimensional method of complex research of heat and mass transfer. This allows examining the interaction of some transfer processes in a natural cooling basin (the Drūkšiai lake): the wind power and direction, variable water density, the coefficient of heat conduction and heat transfer of the water‐air interface. Combined effect of these natural actions determines the heat amount that the basin is able to dissipate to the surrounding atmospheric media in thermal equilibrium (without changes in the mean water temperature). This paper presents a number of the most widely used expressions for the coefficients of vertical and horizontal heat transfer. On the basis of stream velocity and mean temperature profiles measured in the cooling pond as well as on that of their time variations suggestions are made that the mixing rate at the water surface is caused by natural space ‐ time variation of the wind, and can be described by the value of eddy viscosity coefficient ‐ 1 m2/s (numerical modeling with 0,9–1,3 m2/s). The wind influences the surface of the lake according to the experimental data, i e 1–3 % of the mean wind velocity. The model applies to the weakly wind, approximately 1–5 m/s of the mean wind velocity. Comparison of experimental and numerical results showed a qualitative agreement. For a better quantitative approximation, it is necessary to have more boundary conditions variable with time and to solve unsteady set equations for transfer processes.

scholarly journals RANDOMIZATION OF EXPERIMENTS IN CHEMICAL TECHNOLOGY

2021 ◽  
Vol 1 (1) ◽  
pp. 5-6
Author(s):  
Aleksey Bal'chugov
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Chemical Technology ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Experi Mental Study

It is shown that randomization allows obtaining more reliable results in the experi mental study of hydrodynamic, heat transfer and mass transfer processes.

scholarly journals Molecular interaction mechanism of a 14-3-3 protein with a phosphorylated peptide elucidated by enhanced conformational sampling

2020 ◽  
Author(s):  
Junichi Higo ◽  
Takeshi Kawabata ◽  
Ayumi Kusaka ◽  
Kota Kasahara ◽  
Narutoshi Kamiya ◽  
...  
Keyword(s):  
Complex Structure ◽  
Three Dimensional ◽  
Interaction Mechanism ◽  
Salt Bridge ◽  
High Density ◽  
Receptor Protein ◽  
Stable Complex ◽  
Conformational Sampling ◽  
Stable Clusters ◽  
Phosphorylated Peptide

ABSTRACTEnhanced conformational sampling, a genetic-algorithm-guided multi-dimensional virtual-system coupled molecular dynamics, can provide equilibrated conformational distributions of a receptor protein and a flexible ligand at room temperature. The distributions provide not only the most stable but also semi-stable complex structures, and propose a ligand–receptor binding process. This method was applied to a system consisting of a receptor protein, 14-3-3ε, and a flexible peptide, phosphorylated Myeloid leukemia factor 1 (pMLF1). The results present comprehensive binding pathways of pMLF1 to 14-3-3ε. We identified four thermodynamically stable clusters of MLF1 on the 14-3-3ε surface, and free-energy barriers among some clusters. The most stable cluster includes two high-density spots connected by a narrow corridor. When pMLF1 passes the corridor, a salt-bridge relay (switching) related to the phosphorylated residue of pMLF1 occurs. Conformations in one high-density spots are similar to the experimentally determined complex structure. Three-dimensional distributions of residues in the intermolecular interface rationally explain the binding-constant changes resultant from alanine–mutation experiment for the residues. We performed a simulation of non-phosphorylated peptide and 14-3-3ε, which demonstrated that the complex structure was unstable, suggesting that phosphorylation of the peptide is crucially important for binding to 14-3-3ε.

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