Turbulent Film Condensation on a Horizontal Elliptical Tube

2003 ◽  
Vol 125 (6) ◽  
pp. 1194-1197 ◽  
Author(s):  
Cha’o-Kuang Chen ◽  
Hai-Ping Hu
Keyword(s):  
Boundary Layer ◽  
High Velocity ◽  
Potential Flow ◽  
Tangential Velocity ◽  
Flow Theory ◽  
Interfacial Shear ◽  
Experimental Results ◽  
Film Condensation ◽  
Vapor Flow ◽  
Tube Surface

This is an investigation of turbulent film condensation on a horizontal elliptical tube. The high tangential velocity of the vapor flow at the boundary layer is determined from potential flow theory. The Colburn analogy is used to define the local liquid-vapor interfacial shear which occurs for high velocity vapor flow across an elliptical tube surface. The results developed in this study are compared with those generated by previous theoretical and experimental results.

Flow Separation

2009 ◽  
Author(s):  
Ahmad Fakheri
Keyword(s):  
Boundary Layer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Numerical Solution ◽  
Flow Separation ◽  
Potential Flow ◽  
Experimental Results ◽  
Science Courses ◽  
Boundary Layer Equations ◽  
Solution Of Equations

In thermal science courses, flow over curved objects, like cylinders or spheres are generally discussed qualitatively, followed by the presentation of numerical or experimental results for the drag coefficient, Nusselt number, and flow separation. Rarely, there is much discussion of how solutions are obtained. In this paper the flow separation is first introduced by solving the Falkner-Skan flow. The process for numerical solution of equations is presented to show that the flow separates at a plate angle of about −18°. Comparisons are drawn between this and flow over a cylinder. The non-similar boundary layer equations are then solved flow over a cylinder, using potential flow results for the velocity outside of the boundary layer. This solution shows that the flow separates at 103.5°, which is significantly more than the experimental value of 80°. Using a more realistic velocity for flow outside of the boundary layer, the numerical solution obtained predicts flow separation at an angle of 79°, which is close to the experimental results. All the solutions are obtained using spreadsheets that greatly simplify the analysis.

Modeling of Interfacial Shear for Gas Liquid Flows in Annular Film Condensation

1996 ◽  
Vol 63 (2) ◽  
pp. 529-538 ◽  
Author(s):  
A. Narain
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Internal Flow ◽  
Admissible Solution ◽  
Interfacial Shear ◽  
Film Condensation ◽  
Vapor Flow ◽  
Pressure Drops ◽  
Transfer Rates ◽  
Stability Type

Internal flow of pure vapor experiencing film condensation on the walls of a straight horizontal duct is studied. The commonly occurring annular case of turbulent (or laminar) vapor flow in the core and laminar flow of the liquid condensate—with or without waves on the interface—is emphasized. We present a new methodology which models interfacial shear with the help of theory, computations, and reliable experimental data on heat transfer rates. The theory—at the point of onset of condensation—deals with issues of asymptotic form of interfacial shear, nonuniqueness of solutions, and selection of the physically admissible solution by a stability type criteria. Other details of the flow are predicted with the help of the proposed modeling approach. These predictions are shown to be in agreement with relevant experimental data. The trends for film thickness, heat transfer rates, and pressure drops are also made available in the form of power-law correlations.

Forced Condensation in a Tube With Suction at the Wall for Microgravitational Applications

1988 ◽  
Vol 110 (4a) ◽  
pp. 982-985 ◽  
Author(s):  
A. Faghri ◽  
L. C. Chow
Keyword(s):  
Boundary Layer ◽  
Constant Temperature ◽  
Flow Rate ◽  
Tube Wall ◽  
Interfacial Shear ◽  
Continuous Operation ◽  
Vapor Flow ◽  
Uniform Suction ◽  
Inertial Terms ◽  
Energy Equations

The condensation of vapor within a tube is examined for a tube wall that has a constant temperature and uniform suction in a microgravitational environment. The motion of the condensate is due to the interfacial shear between the vapor and the liquid as well as the suction at the wall. The decrease in the vapor flow rate due to condensation has been taken into account. The governing boundary layer momentum and energy equations have been solved by approximating the convective and inertial terms. It is concluded that simultaneous suction and vapor shear can effectively drain the condensate to ensure the continuous operation of space condensers.

Vortex Formation near the Intakes to Turbomachinery and Duct Systems

1974 ◽  
Vol 188 (1) ◽  
pp. 597-605 ◽  
Author(s):  
M. J. C. Swainston
Keyword(s):  
Boundary Layer ◽  
Gas Turbine ◽  
Potential Flow ◽  
Vortex Formation ◽  
Experimental Results ◽  
Formation Mechanisms ◽  
Layer Potential ◽  
Vortex Strength ◽  
Duct Systems ◽  
Experimental Findings

Experimental results are presented which show vortex formations occurring within a model marine gas-turbine downtake. The basic phenomenon of vortex formation is discussed and the boundary-layer-potential-flow interaction identified as the cause. Further experiments on a model gas-turbine test stand are reported in which the vortex strength was assessed. On this basis, a simplified theory for the occurrence and strength of vortex formations is presented which agrees qualitatively with the principal experimental findings. The formation of air-entraining vortices in hydraulic installations is briefly examined in the light of the explanations previously advanced. Although a number of possible vortex formation mechanisms are identified, it is concluded that further research is required in this area.

scholarly journals Comparison of Predicted and Measured Velocities in a Compressor Disk Drum Model

1987 ◽  
Author(s):  
D. G. Alberga ◽  
G. E. Stephens ◽  
B. V. Johnson
Keyword(s):  
Boundary Layer ◽  
Tangential Velocity ◽  
Experimental Results ◽  
Low Flow ◽  
Working Fluid ◽  
Laser Doppler Velocimeter ◽  
Flow Rates ◽  
Flow Equations ◽  
The Core ◽  
Momentum Integral

The tangential velocity distributions in the bleed and the trapped cavities of an eleven-cavity, compresor drum model were measured and predicted. The measurements were obtained with a Laser Doppler Velocimeter (LDV) in experiments using Freon-113 as the working fluid. The experiments were conducted at disk tangential Reynolds numbers of approximately 2 × 106 over a range of inward bleed flow rates through the center cavity. The experimental results show that the tangential velocity profiles in the bleed cavity vary from near-solid-body at low flow rates to near-free-vortex at the highest flow rate. The experimental results also showed a decrease in tangential velocity strength in the trapped flow cavities with distance from the bleed cavity. The flow in the bleed and trapped cavities were predicted using an analysis coupling the flow in a core region with the flow in the disk boundary layers. The secondary flow in the boundary layer was modeled using momentum integral equations. The core flow was determined by coupling the total flow with the boundary layer flow through the continuity equation, and the core tangential velocity was modeled with one dimensional viscous flow equations. Predicted results are presented for a range of flow conditions and cavity locations. The analytical model accurately predicted the tangential velocity distribution, and hence pressure drop, in both classes of cavities when the appropriate core turbulence model and boundary conditions were applied.

A Method for Designing Wind Tunnel Contractions

1951 ◽  
Vol 55 (483) ◽  
pp. 169-180 ◽  
Author(s):  
R. Harrop
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Pressure Gradient ◽  
Cross Section ◽  
Incompressible Flow ◽  
Circular Cross Section ◽  
Flow Theory ◽  
Boundary Layer Separation ◽  
Experimental Results ◽  
Pressure Gradients

SummaryThe contraction of a wind tunnel should be free from adverse pressure gradients, since this might cause boundary layer separation.A wall contour has been designed for a circular cross-section contraction using incompressible flow theory. This gave a favourable pressure gradient at the beginning of the contraction where separation is likely to occur.Appendix I compares the theory with experimental results obtained from a model of a proposed supersonic tunnel of which the contraction is rectangular in cross-section and which has been based on the results obtained in this report.

Quantification of added-mass effects using particle image velocimetry data for a translating and rotating flat plate

2019 ◽  
Vol 870 ◽  
pp. 492-518 ◽  
Author(s):  
S. J. Corkery ◽  
H. Babinsky ◽  
W. R. Graham
Keyword(s):  
Boundary Layer ◽  
Particle Image Velocimetry ◽  
Flow Field ◽  
Flat Plate ◽  
Potential Flow ◽  
Particle Image ◽  
Flow Theory ◽  
Added Mass ◽  
Flow Topology ◽  
Image Velocimetry

Added mass characterises the additional force required to accelerate a body when immersed in an ideal fluid. It originates from an asymmetric change to the surrounding pressure field so the fluid velocity satisfies the no-through-flow condition. This is intrinsically linked with the production of boundary vorticity. A body in potential flow may be represented by an inviscid vortex sheet and added-mass forces determined using impulse methods. However, most fluids are not inviscid. It has been theorised that viscosity causes the ‘added-mass vorticity’ to form in an intensely concentrated boundary layer region, equivalent to the inviscid distribution. Experimentally this is difficult to confirm due to limited measurement resolution and the presence of additional boundary layer vorticity, some the result of induced velocities from free vorticity in the flow field. The aim of this paper is to propose a methodology to isolate the added-mass vorticity experimentally with particle image velocimetry, and confirm that it agrees with potential flow theory even in separated flows. Experiments on a flat-plate wing undergoing linear and angular acceleration show close agreement between the theoretical and measured added-mass vorticity distributions. This is demonstrated to be independent of changes to flow topology due to flow separation. Flow field impulse and net force are also consistent with theory. This paper provides missing experimental evidence coupling added mass and the production of boundary layer vorticity, as well as confirmation that inviscid unsteady flow theory describes the added-mass effect correctly even in well-developed viscous flows.

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