scholarly journals An analytical study on the entropy generation in flow of a generalized Newtonian fluid

2019 ◽  
Vol 23 (Suppl. 6) ◽  
pp. 1959-1969
Author(s):  
Yigit Aksoy ◽  
Necmi Gurkan ◽  
Ayse Aksoy ◽  
Derya Durgun ◽  
Ali Yurddas
Keyword(s):  
Heat Transfer ◽  
Viscous Friction ◽  
Analytical Investigation ◽  
Heat Fluxes ◽  
Variable Step Size ◽  
Parallel Plates ◽  
Step Size ◽  
Generalized Newtonian Fluid ◽  
Dissipation Term ◽  
Pressure Driven Flow

In this study, an analytical investigation on pressure driven flow of Powell-Eyring fluid is conducted to understand the irreversibilities due to heat transfer and viscous heating. The flow between infinitely long parallel plates is considered as fully developed and laminar with constant properties and subjected to symmetrical heat fluxes from solid boundaries. The internal heating due to viscous friction accompanies external heat transfer, that is, viscous dissipation term is to be involved in the energy equation. As a cross-check, accuracy of analytical solutions is confirmed by a predictor-corrector numerical scheme with variable step size.

Experimental and Analytical Investigation of Compact Liquid Cooled Heat Sinks

2004 ◽  
Author(s):  
M. Zugic ◽  
J. R. Culham ◽  
P. Teertstra ◽  
Y. Muzychka ◽  
K. Horne ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Tests ◽  
Reynolds Numbers ◽  
High Heat ◽  
Analytical Investigation ◽  
Boundary Resistance ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Air Cooling ◽  
Design Tools

Compact, liquid cooled heat sinks are used in applications where high heat fluxes and boundary resistance preclude the use of more traditional air cooling techniques. Four different liquid cooled heat sink designs, whose core geometry is formed by overlapped ribbed plates, are examined. The objective of this analysis is to develop models that can be used as design tools for the prediction of overall heat transfer and pressure drop of heat sinks. Models are validated for Reynolds numbers between 300 and 5000 using experimental tests. The agreement between the experiments and the models ranges from 2.35% to 15.3% RMS.

Turbine Tip and Shroud Heat Transfer

1991 ◽  
Vol 113 (3) ◽  
pp. 502-507 ◽  
Author(s):  
D. E. Metzger ◽  
M. G. Dunn ◽  
C. Hah
Keyword(s):  
Heat Transfer ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Leakage Flow ◽  
Turbine Cooling ◽  
Structural Durability ◽  
Close Proximity ◽  
Turbine Housing ◽  
Blade Tip ◽  
Pressure Driven Flow

Unshrouded blades of axial turbine stages move in close proximity to the stationary outer seal, or shroud, of the turbine housing. The pressure difference between the concave and convex sides of the blade drives a leakage flow through the gap between the moving blade tip and adjacent wall. This clearance leakage flow and accompanying heat transfer are of interest because of long obvious effects on aerodynamic performance and structural durability, but understanding of its nature and influences has been elusive. Previous studies indicate that the leakage through the gap is mainly a pressure-driven flow whose magnitude is related strongly to the airfoil pressure loading distribution and only weakly, if at all, to the relative motion between blade tip and shroud. A simple flow and heat transfer model incorporating these features can be used to estimate both tip and shroud heat transfer provided that reasonable estimates of the clearance gap size and clearance leakage flow can be made. The present work uses a numerical computation of the leakage flow to link the model to a specific turbine geometry and operating point for which a unique set of measured local tip and shroud heat fluxes is available. The resulting comparisons between the model estimates and measured heat transfer are good. The model should thus prove useful in the understanding and interpretation of future measurements, and should additionally prove useful for providing early design estimates of the levels of tip and shroud heat transfer that need to be compensated for by active turbine cooling.

Introduction of a novel electric field-based plate heat sink for heat transfer enhancement of thermal systems

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nader Nourdanesh ◽  
Faramarz Ranjbar
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Thermal Management ◽  
High Voltage ◽  
Heat Sink ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Parallel Plates ◽  
Thermal Systems ◽  
Content Type

Purpose The purpose of this study is to use an electric field technique to design novel heat sinks capable of rejecting as much heat as possible in a limited space. Configuration of electrodes in this study can be used for increasing the efficiency of heat sinks. Design/methodology/approach This study investigates a novel electrohydrodynamic (EHD)-based heat sink for thermal management of electronic devices and thermal systems. The significant part of designing an EHD heat sink is the arrangement of the electrodes. A numerical simulation is performed for a heat sink with two parallel plates to determine the optimum dimensional configuration of electrodes. The upper plate of this heat sink is the ground electrode with a constant atmosphere temperature, and the lower plate of it with flush-mounted high-voltage electrodes has uniform heat flux. Findings The results show that heat transfer changes by the size of the vortices and the number of them. These vortices are emerged by the electric field, and the number of them increases with increasing the number of electrodes. The interaction of vortices size and number leads to having the lowest average temperature in the optimum case by two high voltage electrodes with widths of 7.5 mm and a 17.5 mm gap between them. In comparison with the case without the electric field, with increasing the applied voltage to 30 kV, the efficiency of this EHD heat sink increases up to 37%. Originality/value Improvements in electrical equipment make them more compact with higher heat fluxes. Hence, the amount of heat to be dissipated per area increases and needs thermal management to operate at their design temperatures. Therefore, to improve the performance and life span of electronic components and increase their efficiency, it is necessary to design heat sinks to decrease their maximum (peak) temperature.

Turbine Tip and Shroud Heat Transfer

1990 ◽  
Author(s):  
D. E. Metzger ◽  
M. G. Dunn ◽  
C. Hah
Keyword(s):  
Heat Transfer ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Leakage Flow ◽  
Turbine Cooling ◽  
Structural Durability ◽  
Close Proximity ◽  
Turbine Housing ◽  
Blade Tip ◽  
Pressure Driven Flow

Unshrouded blades of axial turbine stages move in close proximity to the stationary outer seal, or shroud, of the turbine housing. The pressure difference between the concave and convex sides of the blade drives a leakage flow through the gap between the moving blade tip and adjacent wall. This clearance leakage flow and accompanying heat-transfer are of interest because of long obvious effects on aerodynamic performance and structural durability, but understanding of its nature and influences has been elusive. Previous studies indicate that the leakage through the gap is mainly a pressure-driven flow whose magnitude is related strongly to the airfoil pressure loading distribution and only weakly, if at all, to the relative motion between blade tip and shroud. A simple flow and heat-transfer model incorporating these features can be used to estimate both tip and shroud heat transfer provided that reasonable estimates of the clearance gap size and clearance leakage flow can be made. The present work uses a numerical computation of the leakage flow to link the model to a specific turbine geometry and operating point for which a unique set of measured local tip and shroud heat fluxes are available. The resulting comparisons between the model estimates and measured heat-transfer are good. The model should thus prove useful in the understanding and interpretation of future measurements, and should additionally prove useful for providing early design estimates of the levels of tip and shroud heat transfer that need to be compensated for by active turbine cooling.

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