Manufacturing Influences on Pressure Losses of Channel Fed Holes

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Michael Barringer ◽  
Karen A. Thole ◽  
Vaidyanathan Krishnan ◽  
Evan Landrum
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Cross Sectional Area ◽  
Channel Inlet ◽  
Sectional Area ◽  
Exit Hole ◽  
Cross Sectional ◽  
Flow Rates ◽  
Channel Exit ◽  
Loss Coefficients

Variations from manufacturing can influence the overall pressure drop and subsequent flow rates through supply holes in such applications as film-cooling, transpiration cooling, and impingement cooling that are supplied by microchannels, pipe-flow systems, or secondary air systems. The inability to accurately predict flow rates has profound effects on engine operations. The objective of this study was to investigate the influence of several relevant manufacturing features that might occur for a cooling supply hole being fed by a range of channel configurations. The manufacturing variances included the ratio of the hole diameter to the channel width, the number of channel feeds (segments), the effect of hole overlap with respect to the channel sidewalls, and the channel Reynolds number. The results showed that the friction factors for the typically long channels in this study were independent of the tested inlet and exit hole configurations. The results also showed that the nondimensional pressure loss coefficients for the flow passing through the channel inlet holes and through the channel exit holes were found to be independent of the channel flow Reynolds number over the tested range. The geometric scaling ratio of the hole cross-sectional area to the channel cross-sectional area collapsed the pressure loss coefficients the best for both one and two flow segments for both the channel inlet and channel exit hole.

Manufacturing Influences on Pressure Losses of Channel Fed Holes

2013 ◽  
Author(s):  
Michael Barringer ◽  
Karen A. Thole ◽  
Vaidyanathan Krishnan ◽  
Evan Landrum
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Cross Sectional Area ◽  
Channel Inlet ◽  
Sectional Area ◽  
Exit Hole ◽  
Cross Sectional ◽  
Flow Rates ◽  
Channel Exit ◽  
Loss Coefficients

Variations from manufacturing can influence the overall pressure drop and subsequent flow rates through supply holes in such applications as film-cooling, transpiration cooling, and impingement cooling that are supplied by micro-channels, pipe-flow systems, or secondary air systems. The inability to accurately predict flow rates has profound effects on engine operations. The objective of this study was to investigate the influence of several relevant manufacturing features that might occur for a cooling supply hole being fed by a range of channel configurations. The manufacturing variances included the ratio of hole diameter to channel width, the number of channel feeds (segments), the effect of hole overlap with respect to the channel sidewalls, and channel Reynolds number. Results showed that the friction factors for the typically long channels in this study, were independent of the inlet and exit hole configurations tested. Results also showed that the non-dimensional pressure loss coefficients for the flow passing through the channel inlet holes and through the channel exit holes were found to be independent of the channel flow Reynolds number over the range tested. The geometric scaling ratio of the hole cross-sectional area to the channel cross-sectional area collapsed the pressure loss coefficients the best for both one and two flow segments for both the channel inlet and channel exit hole.

scholarly journals Hydrology of a segment of a glacier situated in an overdeepening, Storglaciären, Sweden

1994 ◽  
Vol 40 (134) ◽  
pp. 140-148 ◽  
Author(s):  
Roger Leb. Hooke ◽  
Veijo A. Pohjola
Keyword(s):  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Video Observations ◽  
Pressure Melting ◽  
Bed Slope ◽  
Energy Dissipated ◽  
Total Discharge ◽  
Tracer Experiments

AbstractTracer experiments, and water-level observations made while drilling 47 boreholes in an overdeepened section of Storglaciären, have demonstrated that nearly all of the water passing through this part of the glacier moves in englacial conduits. Much of the viscous energy dissipated by subglacial water flowing up an adverse bed slope out of such an overdeepening may be needed to warm the water to keep it at the pressure-melting point. If the adverse slope is sufficiently steep, freezing may occur within the conduits. The possibility for enlargement of conduits by melting is thus limited and water pressures become high. We infer that this, combined with possible blocking of conduits by freezing, forces the water to seek englacial pathways.The frequency with which englacial conduits are encountered during drilling suggests that there are several hundred of them in any given cross-section of the glacier. Consequently, each must carry a small fraction of the total discharge, say ∼ 10−3 m3 s−1. Tracer experiments suggest that flow rates in these conduits are < 10− m s−1, so conduit cross-sectional areas must be ∼10−2 m2, a size that is consistent with video observations in boreholes. The observed mean hydraulic gradient through the overdeepening is ∼0.04. If the conduits were of uniform cross-sectional area, the roughness implied by these figures would be unreasonably high and water pressures in them would be lower than observed. Thus, we hypothesize that conduits are locally constricted to only a small fraction of their average cross-sectional area.

scholarly journals Hydrology of a segment of a glacier situated in an overdeepening, Storglaciären, Sweden

1994 ◽  
Vol 40 (134) ◽  
pp. 140-148 ◽  
Author(s):  
Roger Leb. Hooke ◽  
Veijo A. Pohjola
Keyword(s):  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Video Observations ◽  
Pressure Melting ◽  
Bed Slope ◽  
Energy Dissipated ◽  
Total Discharge ◽  
Tracer Experiments

AbstractTracer experiments, and water-level observations made while drilling 47 boreholes in an overdeepened section of Storglaciären, have demonstrated that nearly all of the water passing through this part of the glacier moves in englacial conduits. Much of the viscous energy dissipated by subglacial water flowing up an adverse bed slope out of such an overdeepening may be needed to warm the water to keep it at the pressure-melting point. If the adverse slope is sufficiently steep, freezing may occur within the conduits. The possibility for enlargement of conduits by melting is thus limited and water pressures become high. We infer that this, combined with possible blocking of conduits by freezing, forces the water to seek englacial pathways.The frequency with which englacial conduits are encountered during drilling suggests that there are several hundred of them in any given cross-section of the glacier. Consequently, each must carry a small fraction of the total discharge, say ∼ 10−3m3s−1. Tracer experiments suggest that flow rates in these conduits are &lt; 10−m s−1, so conduit cross-sectional areas must be ∼10−2m2, a size that is consistent with video observations in boreholes. The observed mean hydraulic gradient through the overdeepening is ∼0.04. If the conduits were of uniform cross-sectional area, the roughness implied by these figures would be unreasonably high and water pressures in them would be lower than observed. Thus, we hypothesize that conduits are locally constricted to only a small fraction of their average cross-sectional area.

Enhanced Flow Boiling Heat Transfer Using Radial Microchannels

2016 ◽  
Author(s):  
Alyssa Recinella ◽  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Cross Sectional Area ◽  
Working Fluid ◽  
Transfer Performance ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Flow Cross

Flow boiling has the ability to remove high heat fluxes while maintaining a low wall superheat. Various researchers have developed enhanced microchannel geometries to improve the heat transfer performance of the system. Recently, a number of new studies have used the increasing flow cross-sectional area concept to overcome flow instabilities and record high CHF. In this work, a new geometry is experimentally investigated utilizing a radial cross-section, which provides the increasing fluid flow cross-sectional area in the flow direction. The flow boiling performance is studied using radial microchannels and water as the working fluid. Four different flow rates ranging from 120–400 mL/min are studied for this new geometry. Heat transfer performance (boiling curve and heat transfer coefficient) and pressure drop characteristics are discussed for all flow rates. Furthermore, the work is supported by high speed visualization of the bubble dynamics. The boiling performance obtained is compared to the existing data in the literature.

Numerical Study on the Flow Past a Twisted Elliptic Cylinder With Subcritical Reynolds Number

2011 ◽  
Author(s):  
Min Ho Kim ◽  
Jin Woog Lee ◽  
Hyun Sik Yoon ◽  
Man Yeong Ha
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Elliptic Cylinder ◽  
Cross Sectional Area ◽  
Stream Velocity ◽  
Spanwise Direction ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Past ◽  
Smooth Cylinder

Large eddy simulation of flow past a torsional cylinder has been carried out at a Reynolds number of 3900 based on the cylinder diameter and the free stream velocity using finite volume method. The torsional cylinder has been formed by rotating the elliptic cross sectional area along the spanwise direction. For an ellipse, different eccentricities are considered to observe the effect of eccentricity on the flow fields. The excellent comparisons with previous studies for the cases of a smooth cylinder and a wavy cylinder having sinusoidal variation in cross sectional area along the spanwise direction guarantee the accuracy of present numerical methods. The effect of eccentricity on the drag and lift coefficients representing the fluid flow characteristics has been investigated by comparing with those of the smooth cylinder, resulting in enhancement of drag reduction and suppression of vortex-induced vibration. The isosurface of swirling strength has been adopted to identify the vortical structures in the turbulent wake.

Heat Transfer and Pressure Loss in a Two-Pass, Rectangular Channel Featuring a Reduced Cross-Sectional Area After the 180- Degree Tip Turn with Different Turning Vane Configurations

2021 ◽  
pp. 1-44
Author(s):  
Sulaiman Alsaleem ◽  
Lesley Wright ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Cross Section ◽  
Pressure Loss ◽  
Guide Vane ◽  
Circular Cross Section ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Number Range

Abstract Serpentine, multi-pass cooling passages, are used in cooling advanced gas turbine blades. In open literature, most internal cooling studies use a fixed cross-sectional area for multi-pass channels. Studies that use varying aspect ratio channels, along with a guide vane to direct the flow with turning, are scarce. Therefore, this study investigates the effect of using different guide vane designs on both detailed heat transfer distribution and pressure loss in a multi-pass channel with an aspect ratio of (4:1) in the entry passage and (2:1) in the second passage downstream of the vane (s). The first vane configuration is one solid-vane with a semi-circular cross-section connecting the two flow passages. The second configuration has three broken-vanes with a quarter-circular cross-section; two broken vanes are located downstream in the first passage, and one broken vane is upstream in the second passage. Detailed heat transfer distributions were obtained on all surfaces within the flow passages by using a transient liquid crystal method. Results show that including the semi-circular vane in the turning region enhanced the overall heat transfer by around 29% with a reduction in pressure loss by around 20%. Moreover, results show the quarter-circular vane design provides higher overall averaged heat transfer enhancement than the semi-circular vane design by around 9% with penalty of higher pressure drop by 6%, which yields higher thermal performance by 7%, over a Reynolds number range from 15,000 to 45,000.

scholarly journals Mass of different snow crystal shapes derived from fall speed measurements

2021 ◽  
Vol 21 (24) ◽  
pp. 18669-18688
Author(s):  
Sandra Vázquez-Martín ◽  
Thomas Kuhn ◽  
Salomon Eliasson
Keyword(s):  
Particle Size ◽  
Reynolds Number ◽  
Empirical Relationship ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Maximum Dimension ◽  
Cross Sectional ◽  
Microphysical Properties ◽  
Ice Particles ◽  
Fall Speed

Abstract. Meteorological forecast and climate models require good knowledge of the microphysical properties of hydrometeors and the atmospheric snow and ice crystals in clouds, for instance, their size, cross-sectional area, shape, mass, and fall speed. Especially shape is an important parameter in that it strongly affects the scattering properties of ice particles and consequently their response to remote sensing techniques. The fall speed and mass of ice particles are other important parameters for both numerical forecast models and the representation of snow and ice clouds in climate models. In the case of fall speed, it is responsible for the rate of removal of ice from these models. The particle mass is a key quantity that connects the cloud microphysical properties to radiative properties. Using an empirical relationship between the dimensionless Reynolds and Best numbers, fall speed and mass can be derived from each other if particle size and cross-sectional area are also known. In this study, ground-based in situ measurements of snow particle microphysical properties are used to analyse mass as a function of shape and the other properties particle size, cross-sectional area, and fall speed. The measurements for this study were done in Kiruna, Sweden, during snowfall seasons of 2014 to 2019 and using the ground-based in situ Dual Ice Crystal Imager (D-ICI) instrument, which takes high-resolution side- and top-view images of natural hydrometeors. From these images, particle size (maximum dimension), cross-sectional area, and fall speed of individual particles are determined. The particles are shape-classified according to the scheme presented in our previous study, in which particles sort into 15 different shape groups depending on their shape and morphology. Particle masses of individual ice particles are estimated from measured particle size, cross-sectional area, and fall speed. The selected dataset covers sizes from about 0.1 to 3.2 mm, fall speeds from 0.1 to 1.6 m s−1, and masses from 0.2 to 450 µg. In our previous study, the fall speed relationships between particle size and cross-sectional area were studied. In this study, the same dataset is used to determine the particle mass, and consequently, the mass relationships between particle size, cross-sectional area, and fall speed are studied for these 15 shape groups. Furthermore, the mass relationships presented in this study are compared with the previous studies. For certain crystal habits, in particular columnar shapes, the maximum dimension is unsuitable for determining Reynolds number. Using a selection of columns, for which the simple geometry allows the verification of an empirical Best-number-to-Reynolds-number relationship, we show that Reynolds number and fall speed are more closely related to the diameter of the basal facet than the maximum dimension. The agreement with the empirical relationship is further improved using a modified Best number, a function of an area ratio based on the falling particle seen in the vertical direction.

scholarly journals Mass transfer in 3D printed electrolyzers: The importance of inlet effects

2020 ◽  
Author(s):  
Stéphane Weusten ◽  
Luc Murrer ◽  
Matheus de Groot ◽  
John van der Schaaf
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Cross Sectional Area ◽  
Transfer Performance ◽  
Sectional Area ◽  
Entrance Length ◽  
Cross Sectional ◽  
3D Printed ◽  
The Cross

This paper investigates the effect of inlet shape, entrance length and turbulence promoters on mass transfer by using 3D printed electrolyzers. Our results show that the inlet design can promote turbulence and lead to an earlier transition to turbulent flow. The Reynolds number at which the transition occurs can be predicted by the ratio of the cross-sectional area of the inlet to the cross-sectional area of the electrolyzer channel. A longer entrance length results in more laminar behavior and a later transition to turbulent flow. With an entrance length of 550mm, the inlet design did no longer affect the mass transfer performance significantly. The addition of gyroid type turbulence promoters resulted in a factor 2 to 4 increase in mass transfer depending on inlet design, entrance length and the type of promoter. From one configuration to another, there was a minimal variation in pressure drop (<16 mbar).

Maximal Expiratory Flow and Lung Volume Changes Associated with Exercise-Induced Asthma in Children and the Effect of Breathing a Low-Density Gas Mixture

1974 ◽  
Vol 46 (3) ◽  
pp. 317-329 ◽  
Author(s):  
S. R. Benatar ◽  
P. König
Keyword(s):  
Flow Rate ◽  
Vital Capacity ◽  
Forced Expiratory Volume ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Lung Volumes ◽  
Flow Rates ◽  
Before And After ◽  
Expiratory Flow

1. Lung volumes and maximum expiratory flow volume (MEFV) curves were measured before and after exercise and after a bronchodilator in eight asthmatic children. 2. Exercise produced significant changes in all volumes and flow rates measured, but the most sensitive measurement was of flow rate at an absolute volume in the terminal portion of the forced vital capacity. Of the more simply obtained measurements maximal flow at 50% of the exhaled vital capacity was the most sensitive, but reductions in forced expiratory volume at 1 s and peak flow rate were almost as marked. 3. The marked reductions in flow rates at low lung volumes after exercise were accompanied by large increases in residual volume and a reduction in the slope of the MEFV curve. These changes suggest functional closure of some lung units and an increase in the time-constant of emptying of other units. 4. The response of flow to breathing helium—oxygen (79:21, v/v) was assessed in the dilated state (before exercise or after bronchodilator) and the constricted state (after exercise) in five of the subjects. 5. An increase in density-dependence of flow rates at all lung volumes during constriction is evidence that, despite the reduction in flow rates, convective acceleration and turbulent flow constitute a greater proportion of the total upstream resistance after exercise than before exercise. The implication is that the cross-sectional area at equal pressure points (EPP) is smaller after exercise than before exercise. This could result from either bronchoconstriction with no change in the location of EPP, or from progression of the EPP further upstream to a region where loss of airways or reduction in their diameter has rendered the total cross-sectional area considerably smaller than under normal circumstances.

Heat Transfer and Pressure Loss in a Two-Pass, Rectangular Channel Featuring a Reduced Cross-Sectional Area After the 180-Degree Tip Turn With Different Turning Vane Configurations

2020 ◽  
Author(s):  
Sulaiman M. Alsaleem ◽  
Lesley M. Wright ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Cross Section ◽  
Pressure Loss ◽  
Circular Cross Section ◽  
Sectional Area ◽  
Cross Sectional ◽  
Number Range

Abstract Serpentine, varying aspect ratio cooling passages, are typically used in cooling advanced gas turbine blades. These passages are usually connected by sharp, 180-deg bends. In the open literature, most of the internal cooling studies use a fixed cross-sectional area for multi-pass channels. Studies that use varying aspect ratio channels, along with a guide (turn) vane to direct the flow with turning, are scarce. In general, studies show that the incorporation of turning vanes in the bend region of a multi-pass channel keeps the heat transfer rate high while reducing pressure loss. Therefore, the current study investigates the effect of using different guide (turn) vane designs on both the detailed heat transfer distribution and pressure loss in a multi-pass channel with an aspect ratio of (4:1) in the entry passage and (2:1) in the second passage downstream of the vane (s). The first vane configuration is one solid-vane with a semi-circular cross-section connecting the two flow passages. The second configuration has three broken-vanes with a quarter-circular cross-section; two broken vanes are located downstream in the first passage (entering the turn), and one broken vane is upstream in the second passage (exiting the turn). For a Reynolds number range 15,000 to 45,000, detailed heat transfer distributions were obtained on all surfaces within the flow passages by using a transient liquid crystal method. The results show that the turning vane configurations have large effects on the heat transfer, in the turning bend and second passage, and the overall pressure drop. Results show that including the semi-circular vane in the turning region of a multi-pass channel enhanced the overall heat transfer by around 29% with a reduction in pressure loss by around 20%. Moreover, results show that the quarter-circular vane design provides higher overall averaged heat transfer enhancement than the semi-circular vane design by around 9% with penalty of higher pressure drop by 6%, which yields higher thermal performance by 7%, over the Reynolds number range.

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