Numerical Analysis of Heat Transfer and Flow Stability in an Open Rotating Cavity Using the Maximum Entropy Production Principle

2010 ◽  
Author(s):  
D. Bohn ◽  
R. Krewinkel ◽  
A. Wolff
Keyword(s):  
Heat Transfer ◽  
Entropy Production ◽  
Maximum Entropy ◽  
Gas Turbines ◽  
Cooling System ◽  
Numerical Study ◽  
Internal Cooling ◽  
Maximum Entropy Production ◽  
Nusselt Numbers ◽  
Rotating Cavity

The flow field and heat transfer in the internal cooling system of gas turbines can be modelled using rotating-disc systems with axial throughflow. Because of the complexity of these flows, in which buoyancy-induced phenomena are of the utmost importance, numerical studies are notoriously difficult to perform and need extensive experimental validation. J.M. Owen proposed using the Maximum Entropy Production (MEP) Principle as a possible means of simplifying numerical computations for these complex flows. This theory is based on the heat flux out of the cavity. In this numerical study, the Nusselt numbers on the disc walls inside an open rotating cavity with a Rayleigh number of approximately 4.97×108 are evaluated with regard to the computed Nusselt numbers on the disc walls. These can be considered to be representative of the flow inside the cavity. It is shown that, as predicted by Owen, the flow is stable when the heat transfer out of the cavity is maximised, or, conversely, the system is unstable when the heat transfer is minimised. Furthermore, it is proven that the level of the Nusselt number plays an important role for the change between the number of vortex pairs in the flow as well.

Numerical Analysis of Heat Transfer and Flow Stability in an Open Rotating Cavity Using the Maximum Entropy Production Principle

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
D. Bohn ◽  
R. Krewinkel ◽  
A. Wolff
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Entropy Production ◽  
Maximum Entropy ◽  
Gas Turbines ◽  
Cooling System ◽  
Numerical Study ◽  
Internal Cooling ◽  
Maximum Entropy Production ◽  
Rotating Cavity

The flow field and heat transfer in the internal cooling system of gas turbines can be modeled using rotating-disk systems with axial throughflow. Because of the complexity of these flows, in which buoyancy-induced phenomena are of the utmost importance, numerical studies are notoriously difficult to perform and need extensive experimental validation. J.M. Owen proposed using the maximum entropy production (MEP) principle as a possible means of simplifying numerical computations for these complex flows since this would enable us to use stationary numerical calculations to predict the flow field. Simply said, this theory is based on the heat flux out of the cavity. In this numerical study, the computed Nusselt numbers on the disk walls inside an open rotating cavity with a Rayleigh number of approximately 4.97 × 108. This is representative of the lower values encountered in the flow inside rotating cavities. It is shown that, as predicted by Owen, the flow is stable when the heat transfer out of the cavity is maximized, or, conversely, the system is unstable when the heat transfer is minimized. Furthermore, it is proven that the level of the Nusselt number plays an important role for the change between the number of vortex pairs in the flow as well.

ICAS-GT: A European Collaborative Research Programme on Internal Cooling Air Systems for Gas Turbines

2002 ◽  
Author(s):  
Peter D. Smout ◽  
John W. Chew ◽  
Peter R. N. Childs
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Research Programme ◽  
Cavity Flow ◽  
Internal Cooling ◽  
Manufacturing Companies ◽  
Flow And Heat Transfer ◽  
Rotating Cavity ◽  
Internal Fluid Flow ◽  
Cooling Air

The Internal Cooling Air Systems for Gas Turbines (ICAS-GT) research programme, sponsored by the European Commission, ran from January 1998 to December 2000, and was undertaken by a consortium of ten gas turbine manufacturing companies and four universities. Research was concentrated in five discrete but related areas of the air system including turbine rim seals, rotating cavity flow and heat transfer, and turbine pre-swirl system effectiveness. In each case, experiments were conducted to extend the database of pressure, temperature, flow and heat transfer measurements to engine representative non-dimensional conditions. The data was used to develop correlations, and to validate CFD and FE calculation methods, for internal fluid flow and heat transfer. This paper summarises the outcome of the project by presenting a sample of experimental results from each technical work package. Examples of the associated CFD calculations are included to illustrate the progress made in developing validated tools for predicting rotating cavity flow and heat transfer over an engine representative range of flow conditions.

scholarly journals Análisis térmico e hidráulico de diferentes geometrías de tubos para mejorar el desempeño de un radiador de automóvil

2020 ◽  
pp. 13-23
Author(s):  
José Luis ZUÑIGA-CERROBLANCO ◽  
Juan Gregorio HORTELANO-CAPETILLO ◽  
Juan Carlos COLLAZO-BARRIENTOS ◽  
Abel HERNANDEZ-GUERRERO
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Automotive Industry ◽  
New Technologies ◽  
Cooling System ◽  
Numerical Study ◽  
Hydraulic Performance ◽  
Cooling Systems ◽  
Cooling Fluid ◽  
Nusselt Numbers

Nowadays the automotive industry requires more powerful and compact engines, which demand that the cooling systems must be improved using new technologies to attend the aim to maintain the engine working at optimum temperature, the cooling system must be adjusted to the dimensions and weight set to avoid the increase of fuel expense. In the present work a numerical study to analyze the thermal and hydraulic performance of a car radiator is carried out. The research focuses on analyzing different geometries for the tubes that make up the radiator, inside of tubes a mixture of 80% water and 20% ethylene glycol is used as the cooling fluid. On the results the global Nusselt numbers for the different geometries, as well as the total pressure drop along the radiator tube are reported. A comparison of the thermal and hydraulic performance for the different geometries analyzed is made. From the results the best geometry to increase heat transfer is chosen, as well as the geometry with the best balance between entropy generation due to heat transfer and pressure drop is chosen.

Effects of Boot-Shaped Rib On Heat Transfer Characteristics of Internal Cooling Turbine Blades

2020 ◽  
Author(s):  
Ky-Quang Pham ◽  
Quang-Hai Nguyen ◽  
Tai-Duy Vu ◽  
Cong-Truong Dinh
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Wall Friction ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Toe Angle

Abstract Gas turbine engine has been widely applied to many heavy industries, such as marine propulsion and aerospace fields. Increasing turbine inlet temperature is one of the major ways to improve the thermal efficiency of gas turbines. Internal cooling for gas turbine cooling system is one of the most commonly used approaches to reduce the temperature of blades by casting various kinds of ribs in serpentine passages to enhance the heat transfer between the coolant and hot surface of gas turbine blades. This paper presents an investigation of boot-shaped rib design to increase the heat transfer performances in the internal cooling turbine blades for gas turbine engines. By varying the design parameter configuration, the airflow is taken with higher momentum, and the minor vortex being at the front rib is relatively removed. The object of this investigation is increasing the reattachment airflow to wall and reducing the vortex occurring near the rib for improving the performances of heat transfer using three-dimensional Reynolds-averaged Navier-Stokes with the SST model. A parametric study of the boot-shaped rib design was performed using various geometric parameters related to the heel-angle, toe-angle, slope-height and rib-width to find their effect on the Nusselt number, temperature on the ribbed wall, friction factor ratio of the channel and thermal performance factor. The numerical results showed that the heat transfer performances are significantly increased with the heel-angle, toe-angle, slope-height, while that remained relatively constant with the rib-width.

Prediction of the Influence of Upstream Wake Passing on Downstream Blade Row External Heat Transfer Coefficient: A New Physically-Based Method

2010 ◽  
Author(s):  
K. S. Chana ◽  
B. R. Haller
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Cooling System ◽  
Guide Vane ◽  
External Heat ◽  
Test Facility ◽  
Internal Cooling ◽  
External Heat Transfer

For gas turbines, accurate prediction of the external heat transfer coefficient on the high pressure (HP) turbine rotor blades is of immense importance, as this component is critical and operates at material limits. Furthermore the external heat load is the governing boundary condition for the design of the internal cooling system of the blade. There is a continuous drive to increase the turbine entry temperature to increase the cycle efficiency, whilst developing blade cooling systems with higher efficiency (i.e. using less cooling air). A new systematic procedure has been developed and validated to predict the external heat transfer to a blade surface. The procedure allows for the unsteady effects caused by the passing of upstream nozzle guide vane (NGV) wakes. The early part of the suction surface was shown to have a pessimistic prediction of external heat transfer coefficient which resulted in unnecessary over-cooling of the blade in this region. The heat transfer aspect is found from the well-known TEXSTAN differential boundary layer method, developed by Mike Crawford at Texas University from the original approach of Spalding & Patankar. The method is validated against the MT1 turbine tested in the QinetiQ Turbine Test Facility. Predictions and comparisons have also been carried out on the VKI turbine stage. The level of agreement with the test data is shown to be good.

scholarly journals Heat Transfer From Low Aspect Ratio Pin Fins

2007 ◽  
Author(s):  
Michael E. Lyall ◽  
Alan A. Thrift ◽  
Atul Kohli ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbines ◽  
Channel Height ◽  
Internal Cooling ◽  
Number Range ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Low Aspect Ratio ◽  
Pin Fins

The performance of many engineering devices from power electronics to gas turbines is limited by thermal management. Heat transfer augmentation in internal flows is commonly achieved through the use of pin fins, which increase both surface area and turbulence. The present research is focused on internal cooling of turbine airfoils using a single row of circular pin fins that is oriented perpendicular to the flow. Low aspect ratio pin fins were studied whereby the channel height to pin diameter was unity. A number of spanwise spacings were investigated for a Reynolds number range between 5000 to 30,000. Both pressure drop and spatially-resolved heat transfer measurements were taken. The heat transfer measurements were made on the endwall of the pin fin array using infrared thermography and on the pin surface using discrete thermocouples. The results show that the heat transfer augmentation relative to open channel flow is the highest for smallest spanwise spacings and lowest Reynolds numbers. The results also indicate that the pin fin heat transfer is higher than the endwall heat transfer.

Combined Experimental and CFD Study of a HP Blade Multi-Pass Cooling System

2009 ◽  
Author(s):  
D. Jackson ◽  
P. Ireland ◽  
B. Cheong
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Cooling System ◽  
Detailed Comparison ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
3 Dimensional ◽  
Turbine Cooling ◽  
Cooling Hole ◽  
The Difference

Progress in the computing power available for CFD predictions now means that full geometry, 3 dimensional predictions are now routinely used in internal cooling system design. This paper reports recent work at Rolls-Royce which has compared the flow and htc predictions in a modern HP turbine cooling system to experiments. The triple pass cooling system includes film cooling vents and inclined ribs. The high resolution heat transfer experiments show that different cooling performance features are predicted with different levels of fidelity by the CFD. The research also revealed the sensitivity of the prediction to accurate modelling of the film cooling hole discharge coefficients and a detailed comparison of the authors’ computer predictions to data available in the literature is reported. Mixed bulk temperature is frequently used in the determination of heat transfer coefficient from experimental data. The current CFD data is used to compare the mixed bulk temperature to the duct centreline temperature. The latter is measured experimentally and the effect of the difference between mixed bulk and centreline temperature is considered in detail.

The mechanics of granitoid systems and maximum entropy production rates

2010 ◽  
Vol 368 (1910) ◽  
pp. 53-93 ◽  
Author(s):  
Bruce E. Hobbs ◽  
Alison Ord
Keyword(s):  
Entropy Production ◽  
Maximum Entropy ◽  
Melt Inclusions ◽  
Selection Process ◽  
Finite Thickness ◽  
Control Valve ◽  
Entropy Production Rate ◽  
Constitutive Behaviour ◽  
Maximum Entropy Production ◽  
Physical Height

A model for the formation of granitoid systems is developed involving melt production spatially below a rising isotherm that defines melt initiation. Production of the melt volumes necessary to form granitoid complexes within 10 4 –10 7 years demands control of the isotherm velocity by melt advection. This velocity is one control on the melt flux generated spatially just above the melt isotherm, which is the control valve for the behaviour of the complete granitoid system. Melt transport occurs in conduits initiated as sheets or tubes comprising melt inclusions arising from Gurson–Tvergaard constitutive behaviour. Such conduits appear as leucosomes parallel to lineations and foliations, and ductile and brittle dykes. The melt flux generated at the melt isotherm controls the position of the melt solidus isotherm and hence the physical height of the Transport/Emplacement Zone. A conduit width-selection process, driven by changes in melt viscosity and constitutive behaviour, operates within the Transport Zone to progressively increase the width of apertures upwards. Melt can also be driven horizontally by gradients in topography; these horizontal fluxes can be similar in magnitude to vertical fluxes. Fluxes induced by deformation can compete with both buoyancy and topographic-driven flow over all length scales and results locally in transient ‘ponds’ of melt. Pluton emplacement is controlled by the transition in constitutive behaviour of the melt/magma from elastic–viscous at high temperatures to elastic–plastic–viscous approaching the melt solidus enabling finite thickness plutons to develop. The system involves coupled feedback processes that grow at the expense of heat supplied to the system and compete with melt advection. The result is that limits are placed on the size and time scale of the system. Optimal characteristics of the system coincide with a state of maximum entropy production rate.

scholarly journals Relaxation Processes and the Maximum Entropy Production Principle

Entropy ◽  
2010 ◽  
Vol 12 (3) ◽  
pp. 473-479 ◽  
Author(s):  
Paško Županović ◽  
Srećko Botrić ◽  
Davor Juretić ◽  
Domagoj Kuić
Keyword(s):  
Entropy Production ◽  
Maximum Entropy ◽  
Relaxation Processes ◽  
Maximum Entropy Production
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