The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Sandra K. S. Boetcher - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Shroud Geometry to Passively Improve Heat Transfer in a Solar Thermal Storage Tank
Journal of Solar Energy Engineering-transactions of The Asme, 2013Co-Authors: Matthew K. Zemler, Sandra K. S. BoetcherAbstract:A Shroud and baffle configuration is used to passively increase heat transfer in a thermal store. The Shroud and baffle are used to create a vena contracta near the surface of the heat exchanger, which will speed up the flow locally and thereby increasing heat transfer. The goal of this study is to investigate the geometry of the Shroud in optimizing heat transfer by locally increasing the velocity near the surface of the heat exchanger. Two-dimensional transient simulations are conducted. The immersed heat exchanger is modeled as an isothermal cylinder, which is situated at the top of a solar thermal storage tank containing water (Pr = 3) with adiabatic walls. The Shroud and baffle are modeled as adiabatic, and the geometry of the Shroud and baffle are parametrically varied. Nusselt numbers and fractional energy discharge rates are obtained for a range of Rayleigh numbers, 105 ≤ RaD ≤ 107 in order to determine optimal Shroud and baffle configurations. It was found that a baffle width of 75% of the width of the heat exchanger provided the best heat transfer performance.
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Investigation of Shroud Geometry to Passively Improve Heat Transfer in a Solar Thermal Storage Tank
Volume 1: Heat Transfer in Energy Systems; Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Transport Phenomena in, 2012Co-Authors: Matthew K. Zemler, Sandra K. S. BoetcherAbstract:A Shroud and baffle configuration is used to passively increase heat transfer in a thermal store. The Shroud and baffle are used to create a vena contracta near the surface of the heat exchanger which will speed up the flow locally and thereby increasing heat transfer. The goal of this study is to investigate the geometry of the Shroud in optimizing heat transfer by locally increasing the velocity near the surface of the heat exchanger. Two-dimensional transient simulations are conducted. The immersed heat exchanger is modeled as an isothermal cylinder which is situated at the top of a solar thermal storage tank containing water (Pr = 3) with adiabatic walls. The Shroud and baffle are modeled as adiabatic and the geometry of the Shroud and baffle are parametrically varied. Nusselt numbers are obtained for a range of Rayleigh numbers, 105 ≤ RaD ≤ 107 in order to determine optimal Shroud and baffle configurations.Copyright © 2012 by ASME
Matthew K. Zemler - One of the best experts on this subject based on the ideXlab platform.
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Investigation of Shroud Geometry to Passively Improve Heat Transfer in a Solar Thermal Storage Tank
Journal of Solar Energy Engineering-transactions of The Asme, 2013Co-Authors: Matthew K. Zemler, Sandra K. S. BoetcherAbstract:A Shroud and baffle configuration is used to passively increase heat transfer in a thermal store. The Shroud and baffle are used to create a vena contracta near the surface of the heat exchanger, which will speed up the flow locally and thereby increasing heat transfer. The goal of this study is to investigate the geometry of the Shroud in optimizing heat transfer by locally increasing the velocity near the surface of the heat exchanger. Two-dimensional transient simulations are conducted. The immersed heat exchanger is modeled as an isothermal cylinder, which is situated at the top of a solar thermal storage tank containing water (Pr = 3) with adiabatic walls. The Shroud and baffle are modeled as adiabatic, and the geometry of the Shroud and baffle are parametrically varied. Nusselt numbers and fractional energy discharge rates are obtained for a range of Rayleigh numbers, 105 ≤ RaD ≤ 107 in order to determine optimal Shroud and baffle configurations. It was found that a baffle width of 75% of the width of the heat exchanger provided the best heat transfer performance.
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Investigation of Shroud Geometry to Passively Improve Heat Transfer in a Solar Thermal Storage Tank
Volume 1: Heat Transfer in Energy Systems; Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Transport Phenomena in, 2012Co-Authors: Matthew K. Zemler, Sandra K. S. BoetcherAbstract:A Shroud and baffle configuration is used to passively increase heat transfer in a thermal store. The Shroud and baffle are used to create a vena contracta near the surface of the heat exchanger which will speed up the flow locally and thereby increasing heat transfer. The goal of this study is to investigate the geometry of the Shroud in optimizing heat transfer by locally increasing the velocity near the surface of the heat exchanger. Two-dimensional transient simulations are conducted. The immersed heat exchanger is modeled as an isothermal cylinder which is situated at the top of a solar thermal storage tank containing water (Pr = 3) with adiabatic walls. The Shroud and baffle are modeled as adiabatic and the geometry of the Shroud and baffle are parametrically varied. Nusselt numbers are obtained for a range of Rayleigh numbers, 105 ≤ RaD ≤ 107 in order to determine optimal Shroud and baffle configurations.Copyright © 2012 by ASME
William R. Bond - One of the best experts on this subject based on the ideXlab platform.
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Cleaning of a thermal vacuum chamber with Shrouds in place
1992Co-Authors: William R. BondAbstract:In February, 1991, a failure of a rotary booster pump caused the diffusion pumps to backstream into a 10 ft x 15 ft thermal vacuum chamber. Concerns existed about the difficulty of removing and reinstalling the Shrouds without causing leaks. The time required for the Shroud removal was also of concern. These concerns prompted us to attempt to clean the chamber without removing the Shrouds.
Budimir Rosic - One of the best experts on this subject based on the ideXlab platform.
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The Influence of Shroud and Cavity Geometry on Turbine Performance: An Experimental and Computational Study—Part I: Shroud Geometry
Journal of Turbomachinery, 2008Co-Authors: Budimir Rosic, John D. Denton, Eric M. CurtisAbstract:Imperfections in the turbine annulus geometry, caused by the presence of the Shroud and associated cavity, have a significant influence on the aerodynamics of the main passage flow path. In this paper, the datum Shroud geometry, representative of steam turbine industrial practice, was systematically varied and numerically tested. The study was carried out using a three-dimensional multiblock solver, which modeled the flow in a 1.5 stage turbine. The following geometry parameters were varied: inlet and exit cavity length, Shroud overhang upstream of the rotor leading edge and downstream of the trailing edge, Shroud thickness for fixed casing geometry and Shroud cavity depth, and Shroud cavity depth for the fixed Shroud thickness. The aim of this study was to investigate the influence of the above geometric modifications on mainstream aerodynamics and to obtain a map of the possible turbine efficiency changes caused by different Shroud geometries. The paper then focuses on the influence of different leakage flow fractions on the mainstream aerodynamics. This work highlighted the main mechanisms through which leakage flow affects the mainstream flow and how the two interact for different geometrical variations and leakage flow mass fractions.
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control of Shroud leakage loss by reducing circumferential mixing
Journal of Turbomachinery-transactions of The Asme, 2008Co-Authors: Budimir Rosic, J D DentonAbstract:Shroud leakage flow undergoes little change in the tangential velocity as it passes over the Shroud. Mixing due to the difference in tangential velocity between the main stream flow and the leakage flow creates a significant proportion of the total loss associated with Shroud leakage flow. The unturned leakage flow also causes negative incidence and intensifies the secondary flows in the downstream blade row. This paper describes the experimental results of a concept to turn the rotor Shroud leakage flow in the direction of the main blade passage flow in order to reduce the aerodynamic mixing losses. A three-stage air model turbine with low aspect ratio blading was used in this study. A series of different stationary turning vane geometries placed into the rotor Shroud exit cavity downstream of each rotor blade row was tested. A significant improvement in flow angle and loss in the downstream stator blade rows was measured together with an increase in turbine brake efficiency of 0.4 %.
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The Influence of Shroud and Cavity Geometry on Turbine Performance — An Experimental and Computational Study: Part I — Shroud Geometry
Volume 6: Turbo Expo 2007 Parts A and B, 2007Co-Authors: Budimir Rosic, John D. Denton, Eric CurtisAbstract:The geometry of the exit Shroud cavity where the rotor Shroud leakage flow re-enters the main passage flow is very important due to the dominant influence of the leakage flow on the aerodynamics of low aspect ratio turbines. The work presented in this paper investigates, both experimentally and numerically, possibilities for the control of Shroud leakage flow by modifications to the exit Shroud cavity. The processes through which the leakage flow affects the mainstream aerodynamics identified in the first part of this study were used to develop promising strategies for reducing the influence of Shroud leakage flow. The experimental program of this study was conducted on a three-stage model air turbine, which was extensively supported by CFD analysis. Three different concepts for Shroud leakage flow control in the exit cavity were analysed and tested: a) profiled exit cavity downstream end-wall, b) axial deflector, and c) radial deflector concept. Reductions in aerodynamic losses associated with Shroud leakage were achieved by controlling the position and direction at which the leakage jet re-enters the mainstream when it leaves the exit Shroud cavity. Suggestions are made for an optimum Shroud and cavity geometry.Copyright © 2007 by ASME
J D Denton - One of the best experts on this subject based on the ideXlab platform.
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control of Shroud leakage loss by reducing circumferential mixing
Journal of Turbomachinery-transactions of The Asme, 2008Co-Authors: Budimir Rosic, J D DentonAbstract:Shroud leakage flow undergoes little change in the tangential velocity as it passes over the Shroud. Mixing due to the difference in tangential velocity between the main stream flow and the leakage flow creates a significant proportion of the total loss associated with Shroud leakage flow. The unturned leakage flow also causes negative incidence and intensifies the secondary flows in the downstream blade row. This paper describes the experimental results of a concept to turn the rotor Shroud leakage flow in the direction of the main blade passage flow in order to reduce the aerodynamic mixing losses. A three-stage air model turbine with low aspect ratio blading was used in this study. A series of different stationary turning vane geometries placed into the rotor Shroud exit cavity downstream of each rotor blade row was tested. A significant improvement in flow angle and loss in the downstream stator blade rows was measured together with an increase in turbine brake efficiency of 0.4 %.
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the control of Shroud leakage flows to reduce aerodynamic losses in a low aspect ratio Shrouded axial flow turbine
Journal of Turbomachinery-transactions of The Asme, 2001Co-Authors: A M Wallis, J D Denton, A A J DemargneAbstract:The losses generated by fluid leaking across the Shrouds of turbine blade rows are known to form a significant proportion of the overall loss generated in low aspect ratio turbines. The use of Shrouds to encase the tips of turbine blades has encouraged the development of many innovative sealing arrangements, all of which are intended to reduce the quantity of fluid (the leakage fraction) leaking across the Shroud. Modern sealing arrangements have reduced leakage fractions considerably, meaning that further improvements can only be obtained by controlling the leakage flow in such a way so as to minimize the aerodynamic losses incurred by the extraction and re-injection of the leakage flow into the mainstream. There are few published experimental investigations on the interaction between mainstream and leakage flows to provide guidance on the best means of managing the leakage flows to do this. This paper describes the development and testing of a strategy to turn the fluid leaking over Shrouded turbine rotor blade rows with the aim of reducing the aerodynamic losses associated with its re-injection into the mainstream flow. The intent was to extract work from the leakage flow in the process. A four stage research turbine was used to test in detail the sealing design resulting from this strategy. A reduction in brake efficiency of 3.5 percent was measured. Further investigation suggested that much of the increase in loss could be attributed to the presence of axial gaps upstream and downstream of the Shroud cavity which facilitated the periodic ingress and egress of mainstream fluid into the Shroud cavity under the influence of the rotor potential field. This process was exacerbated by reductions in the leakage fraction.
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the control of Shroud leakage flows to reduce aerodynamic losses in a low aspect ratio Shrouded axial flow turbine
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2000Co-Authors: A M Wallis, J D Denton, A A J DemargneAbstract:The losses generated by fluid leaking across the Shrouds of turbine blade rows are known to form a significant proportion of the overall loss generated in low aspect ratio turbines. The use of Shrouds to encase the tips of turbine blades has encouraged the development of many innovative sealing arrangements, all of which are intended to reduce the quantity of fluid (the leakage fraction) leaking across the Shroud. Modern sealing arrangements have reduced leakage fractions considerably, meaning that further improvements can only be obtained by controlling the leakage flow in such a way so as to minimise the aerodynamic losses incurred by the extraction and re-injection of the leakage flow into the mainstream. There are few published experimental investigations on the interaction between mainstream and leakage flows to provide guidance on the best means of managing the leakage flows to do this. This paper describes the development and testing of a strategy to turn the fluid leaking over Shrouded turbine rotor blade rows with the aim of reducing the aerodynamic losses associated with its re-injection into the mainstream flow. The intent was to extract work from the leakage flow in the process. A four stage research turbine was used to test in detail the sealing design resulting from this strategy. A reduction in brake efficiency of 3.5% was measured. Further investigation suggested that much of the increase in loss could be attributed to the presence of axial gaps upstream and downstream of the Shroud cavity which facilitated the periodic ingress and egress of mainstream fluid into the Shroud cavity under the influence of the rotor potential field. This process was exacerbated by reductions in the leakage fraction.Copyright © 2000 by ASME
