Local Heat Transfer Process for a Gas–Liquid System in a Wall Region of an Agitated Vessel Equipped with the System of CD6-RT Impellers

2014 ◽  
Vol 53 (42) ◽  
pp. 16539-16549 ◽  
Author(s):  
Iwona Bielka ◽  
Magdalena Cudak ◽  
Joanna Karcz
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Liquid System ◽  
Heat Transfer Process ◽  
Wall Region ◽  
Agitated Vessel

Distribution of local heat transfer coefficient values in the wall region of an agitated vessel

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Magdalena Cudak ◽  
Joanna Karcz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Regime ◽  
Transfer Coefficients ◽  
Measuring Point ◽  
Agitated Vessel ◽  
Heat Transfer Coefficients

AbstractExperimentally found local heat transfer coefficients are analyzed as a function of the measuring point on the heat transfer surface area of the agitated vessel wall and of the impeller eccentricity. Eccentric Rushton turbine and A 315 impeller are considered. Local heat transfer coefficients were measured by means of the computer-aided electrochemical method. The measurements were performed in an agitated vessel with inner diameter 0.3 m, filled with liquid up to the height equal to the vessel diameter. The experiments were carried out within the turbulent regime of the Newtonian liquid flow in the agitated vessel. The results were compared with the data obtained for the agitated vessel equipped with an eccentrically located axial flow propeller or an HE 3 impeller. Experimental studies show that the distributions of the heat transfer coefficient values depend on the impeller eccentricity, impeller type and the direction of the liquid circulation in the agitated vessel.

Vortical structures and heat transfer in a round impinging jet

2008 ◽  
Vol 596 ◽  
pp. 221-260 ◽  
Author(s):  
M. HADŽIABDIĆ ◽  
K. HANJALIĆ
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Impinging Jet ◽  
Local Heat ◽  
Temperature Fields ◽  
Turbulence Energy ◽  
Wall Region ◽  
Turbulence Structure ◽  
Stagnation Region ◽  
Impinging Flows

In order to gain a better insight into flow, vortical and turbulence structure and their correlation with the local heat transfer in impinging flows, we performed large-eddy simulations (LES) of a round normally impinging jet issuing from a long pipe at Reynolds number Re = 20000 at the orifice-to-plate distance H = 2D, where D is the jet-nozzle diameter. This configuration was chosen to match previous experiments in which several phenomena have been detected, but the underlying physics remained obscure because of limitations in the measuring techniques applied. The instantaneous velocity and temperature fields, generated by the LES, revealed interesting time and spatial dynamics of the vorticity and eddy structures and their imprints on the target wall, characterized by tilting and breaking of the edge ring vortices before impingement, flapping, precessing, splitting and pairing of the stagnation point/line, local unsteady separation and flow reversal at the onset of radial jet spreading, streaks pairing and branching in the near-wall region of the radial jets, and others. The LES data provided also a basis for plausible explanations of some of the experimentally detected statistically-averaged flow features such as double peaks in the Nusselt number and the negative production of turbulence energy in the stagnation region. The simulations, performed with an in-house unstructured finite-volume code T-FlowS, using second-order-accuracy discretization schemes for space and time and the dynamic subgrid-scale stress/flux model for unresolved motion, showed large sensitivity of the results to the grid resolution especially in the wall vicinity, suggesting care must be taken in interpreting LES results in impinging flows.

scholarly journals Influence of the Gap Size Between Side Walls and Ribs on the Heat Transfer in a Stationary and Rotating Straight Rib-roughened Duct

2000 ◽  
Vol 6 (4) ◽  
pp. 253-263 ◽  
Author(s):  
R. Kiml ◽  
S. Mochizuki ◽  
A. Murata
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Flow Direction ◽  
Three Dimensional ◽  
Side Wall ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Wall Region ◽  
Side Walls ◽  
Cooling Passage

The objective of this study is to investigate a heat transfer phenomenon in a straight ribroughened duct which represents a cooling passage of a modern gas turbine blade. Experiments were performed for ribs mounted perpendicularly to the main flow direction on two opposite sides of the duct for the following cases: (1) with no gaps, (2) with gaps=0.33hand (3) with gaps=1hbetween the side walls and ribs (wherehis the rib height). The heat transfer results revealed significant differences among these three cases, showing that the existence of gaps increases the heat transfer. Particularly, the local heat transfer on the wall between the consecutive ribs is higher in the near-side wall region than in the central region. To shed some light on this phenomenon, flow visualization was conducted using the particle tracer method. The flow visualization results revealed the effect of gaps on the three-dimensional flow structure between the ribs. It was concluded that this structure caused the heat transfer enhancement in the near-side wall region.

Investigation of the Heat Transfer Process in a PCM During Melting Phase

2014 ◽  
Author(s):  
Mohammad Bashar ◽  
Kamran Siddiqui
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Energy ◽  
Transfer Process ◽  
Phase Change Materials ◽  
Waste Heat ◽  
Liquid Fraction ◽  
Local Heat Transfer ◽  
Heat Transfer Process ◽  
Interface Temperature

Thermal energy storage systems are gaining significance due to their potential use to store renewable energy and waste heat. Phase change materials (PCMs) are considered to be an efficient way to store thermal energy. However, the heat transfer process during the phase change is not well understood. We report on an experimental study conducted to investigate the heat transfer process in a PCM during melting phase. A PCM storage system subjected to bottom heating from a horizontal heated cylinder was considered using wax as the PCM. An imaging technique was used to capture the movement of the solid-liquid interface. Temperature was measured at multiple locations to quantify the heat transfer process. The interface was found to move with a relatively uniform velocity throughout the melting process however, the heat transfer rate was significantly enhanced in the melted (liquid) phase. The local heat transfer coefficient was found to decrease with an increase in the liquid fraction.

A General Heat Transfer Correlation for Annular Flow Condensation

1968 ◽  
Vol 90 (2) ◽  
pp. 267-274 ◽  
Author(s):  
M. Soliman ◽  
J. R. Schuster ◽  
P. J. Berenson
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Annular Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Process ◽  
Heat Transfer Correlation ◽  
Wide Range ◽  
Prandtl Numbers ◽  
Flow Condensation

The interaction between friction, momentum, and gravity, as they affect the heat transfer process during annular flow condensation inside tubes, is studied. Analytical forms for each of these forces are derived and incorporated in a correlation that predicts the local heat transfer coefficient. The predictions agree well with the available experimental data over a wide range of vapor velocities and over a range of Prandtl numbers from 1 to 10. The analysis also yields a means for predicting the onset of liquid run-back in the presence of an adverse gravitational field.

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