[PDF] Flow And Heat Transfers Associated With Impinging Jets In Crossflows eBook

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Page : pages
File Size : 27,75 MB
Release : 1911
Category :
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This thesis reports the results of an experimental study into the flow and heat transfers associated with both inclined and orthogonally impinging axisymmetric air jets. The majority of previously reported studies have been mainly confined to orthogonally impinging jets in stagnant surroundings. In this investigation, free jets as well as the effects of crossflows are considered. This investigation is Primarily concerned with local heat transfer variations. The experimental tests were. conducted with a single 12.7 mm diameter jet impinging on a flat surface, and heat transfers were evaluated using a heat-mass transfer analogy (t e Chilton-Colburn analogy). The sublimation of naphthalene was employed as the mass transfer technique. The flowfield associated with impinging jets has a significant influence on their heat transfer characteristics., In view of the present limited level of understanding of this 'complex' flowfield, extensive flow visualisation techniques were employed in this present investigation. Those were primarily intended to aid interpretation of the experimental heat transfer results, and also to provide further physical understanding of the flowfields resulting from the interactions between impinging jets and crossflowing streams. The flow and heat transfer tests conducted in the programme of work reported in this thesis covered typical ranges of flow parameters of interest in many practical applications of jet impingement systems. Jet inclinations of 45°, 600, and 90°, nozzle to target spacings of 2,11, and 8 nozzle diameters were studied. The Reynolds nuinbers were 30,200,32,700 and 55,100 and mass velocity ratios In the range 4.0 to 3.8 were studied. The effects of these parameters on the flow and heal transfers associated with impinging jets are reported. Comparisons were drawn between the heat transfer results and those of previously reported studies where appropriate.

Author : L. W. Florschuetz
Publisher :
Page : 180 pages
File Size : 17,4 MB
Release : 1985
Category : Gas-turbines
ISBN :

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Spanwise average heat fluxes, resolved in the streamwise direction to one stream-wise hole spacing were measured for two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate. The jet flow, after impingement, was constrained to exit in a single direction along the channel formed by the jet orifice plate and heat transfer surface. The crossflow originated from the jets following impingement and an initial crossflow was present that approached the array through an upstream extension of the channel. The regional average heat fluxes are considered as a function of parameters associated with corresponding individual spanwise rows within the array. A linear superposition model was employed to formulate appropriate governing parameters for the individual row domain. The effects of flow history upstream of an individual row domain are also considered. The results are formulated in terms of individual spanwise row parameters. A corresponding set of streamwise resolved heat transfer characteristics formulated in terms of flow and geometric parameters characterizing the overall arrays is described.

Author : L. W. Florschuetz
Publisher :
Page : 68 pages
File Size : 36,98 MB
Release : 1981
Category : Aerofoils
ISBN :

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Correlations for heat transfer coefficients for jets of circular offices and impinging on a surface parallel to the jet orifice plate are presented. The air, following impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer (impingement) surface. The downstream jets are subjected to a crossflow originating from the upstream jets. Impingement surface heat transfer coefficients resolved to one streamwise jet orifice spacing, averaged across the channel span, are correlated with the associated individual spanwise orifice row jet and crossflow velocities, and with the geometric parameters. (NTRL site)

Author : Ernst Heinrich Hirschel
Publisher : Springer Science & Business Media
Page : 396 pages
File Size : 46,18 MB
Release : 2013-10-29
Category : Technology & Engineering
ISBN : 3642413781

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Viscous flow is treated usually in the frame of boundary-layer theory and as two-dimensional flow. Books on boundary layers give at most the describing equations for three-dimensional boundary layers, and solutions often only for some special cases. This book provides basic principles and theoretical foundations regarding three-dimensional attached viscous flow. Emphasis is put on general three-dimensional attached viscous flows and not on three-dimensional boundary layers. This wider scope is necessary in view of the theoretical and practical problems to be mastered in practice. The topics are weak, strong, and global interaction, the locality principle, properties of three-dimensional viscous flow, thermal surface effects, characteristic properties, wall compatibility conditions, connections between inviscid and viscous flow, flow topology, quasi-one- and two-dimensional flows, laminar-turbulent transition and turbulence. Though the primary flight speed range is that of civil air transport vehicles, flows past other flying vehicles up to hypersonic speeds are also considered. Emphasis is put on general three-dimensional attached viscous flows and not on three-dimensional boundary layers, as this wider scope is necessary in view of the theoretical and practical problems that have to be overcome in practice. The specific topics covered include weak, strong, and global interaction; the locality principle; properties of three-dimensional viscous flows; thermal surface effects; characteristic properties; wall compatibility conditions; connections between inviscid and viscous flows; flow topology; quasi-one- and two-dimensional flows; laminar-turbulent transition; and turbulence. Detailed discussions of examples illustrate these topics and the relevant phenomena encountered in three-dimensional viscous flows. The full governing equations, reference-temperature relations for qualitative considerations and estimations of flow properties, and coordinates for fuselages and wings are also provided. Sample problems with solutions allow readers to test their understanding.

Author : R.S. Amano
Publisher : WIT Press
Page : 253 pages
File Size : 34,82 MB
Release : 2014-05-28
Category : Science
ISBN : 1845649060

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Due to the requirement for enhanced cooling technologies on modern gas turbine engines, advanced research and development has had to take place in field of thermal engineering. Among the gas turbine cooling technologies, impingement jet cooling is one of the most effective in terms of cooling effectiveness, manufacturability and cost. The chapters contained in this book describe research on state-of-the-art and advanced cooling technologies that have been developed, or that are being researched, with a variety of approaches from theoretical, experimental, and CFD studies. The authors of the chapters have been selected from some of the most active researchers and scientists on the subject. This is the first to book published on the topics of gas turbines and heat transfer to focus on impingement cooling alone.