Download or read book Investigation of the Flow Field and Associated Heat Transfer Within an Asymmetrical Leading Edge Jet Impingement Array written by Jorge S. Torres and published by . This book was released on 2019 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two different geometries, varied by H/d, were investigated at various Reynolds numbers ranging from 20,000 to 80,000. The geometry consisted of an array of 9 identical jets impinging on a leading edge of diameter D/d = 2, with an asymmetrical sidewall configuration to better represent the pressure side (PS) and suction side (SS) of a turbine blade.
Download or read book Multiple Jet Impingement Heat Transfer Characteristic written by and published by . This book was released on 1980 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow and Heat Transfers Associated with Impinging Jets in Crossflows written by and published by . This book was released on 1911 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Heat Transfer Study of a Triple Row Impingement Channel at Large Impingement Heights written by Roberto Claretti and published by . This book was released on 2011 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced cooling techniques are required to increase the Brayton cycle temperature ratio necessary for the increase of the overall cycle's efficiency. Current turbine components are cooled with an array of internal cooling channels in the midchord section of the blade, pin fin arrays at the trailing edge and impingement channels in the leading edge. Impingement channels provide the designer with high convective coefficients on the target surface. Increasing the heat transfer coefficient of these channels has been a subject of research for the past 20 years. In the current study, a triple row impingement channel is studied with a jet to target spacing of 6, 8 and 10. The effects of sidewalls are also analyzed. Temperature sensitive paint alongside thin foil heaters are used to obtain heat transfer distributions throughout the target and side walls of the three different channels. Thermal performances were also calculated for the two largest channels. It was found that the side walls provide a significant amount of cooling especially when the channels are mounted side by side so that their sidewalls behave as fins. Similar to literature it was found that an increase in Z/D decreases heat transfer coefficient and provides a more uniform profile. It was also found that the Z/D = 6 and 8 target wall heat transfer profiles are very similar, hinting to the fact that successful potential core impingement may have occurred at height of eight diameters. A Computational Fluid Dynamics, or CFD, study was also performed to provide better insight into the flow field that creates such characteristic heat transfer profiles. The Realizable k-μ solution with enhanced wall functions gave surface heat transfer coefficients 30% off from the experimental data.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1985 with total page 864 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Heat Transfer in Gas Turbines written by Bengt Sundén and published by Witpress. This book was released on 2001 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: This title presents and reflects current active research on various heat transfer topics and related phenomena in gas turbine systems. It begins with a general introduction to gas turbine heat transfer, before moving on to specific areas.
Download or read book Investigation on the Interaction of an Impinging Jet with Cylinder Wakes written by Karthik Krishna and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jet impingement cooling is a widely used cooling method due to the high heat transfer rates associated with it. Research for improving heat transfer rates for this cooling is still being carried out due to its broad application in various fields like gas turbine blade cooling, electronic component cooling, and paper drying. The unsteady jet oscillation effectively enhances the stagnation region and the time-averaged heat transfer rates. It is shown that a novel passive jet oscillation technique can be achieved using the vortices periodically shed from a cylinder placed upstream in a channel with an initial crossflow. Preliminary CFD results prove the hypothesis of jet oscillation induced by the cylinder vortices and that the lateral jet oscillation is an efficient method for uniform distribution of heat transfer. The statistical analysis concluded jet oscillation is most sensitive to cylinder vortex strength. A frequency spectral analysis is performed to classify oscillating and non-oscillating cases. Finally, unsteady numerical and experimental research is carried out to determine the effect of cylinder-jet distance, cylinder diameter, and velocity ratio on jet oscillation and heat transfer rate. The range of cylinder-jet distance and velocity ratio tested are S/d = 2 – 4 and VR = 4 – 12, respectively. The flow interaction mechanism leading the jet oscillation is analyzed using TKE, vorticity, and velocity contours in time. The flow feature analysis concluded the cylinder wakes deformed the jet core inducing lateral and angular oscillations. The heat transfer results showed the Nusselt number is proportional to the velocity ratio for oscillating jet cases. The non-oscillating jet enhances the heat transfer rate by 94% in the wall jet region due to crossflow interaction. And the optimum oscillating jet case improved the stagnation region Nusselt number by 19%.
Download or read book Influence of Impinging Jet Variables on Local Heat Transfer Coefficients Along a Flat Surface with Uniform Heat Flux written by David Claude McMurray and published by . This book was released on 1966 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Heat Transfer and Discharge Coefficient Effects of Jet Impingement on a Surface with Hemispherical and Teardrop Shaped Bumps written by Steven A. McKanas and published by . This book was released on 2016 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jet impingement is among the most effective methods of enhancing heat transfer in practical applications, enabling high heat transfer coefficients without the high pressure losses associated with flow through turbulated channels. The gas turbine industry is interested in combining jet impingement with dimpled and bumped plates as a method of improving heat transfer, enabling greater efficiency. This study investigates the average effects on heat transfer and discharge coefficients (Cd) created by arrays of jets impinging on target surfaces with hemispherical or teardrop shaped bumps using heated copper plates with embedded thermocouples. Reynolds number (Re) ranged from 5000 to 20,000 and 5000 to 26,000 for heat transfer and Cd tests, respectively, for all configurations. The jet pitch-to-diameter ratio x/d ranged between 3.3 and 12 and the jet exit-to-target-plate spacing ratio (z/d) ranged from 2 to 5 for all configurations. Additional Re and z/d values were tested for various configurations in order to fully quantify trends. The effects of spent air discharging in multiple directions was also analyzed. Depending on configuration, impinging on the bumped plates produced minor increases, no change, or a reduction in heat transfer compared to the baseline smooth plate depending on configuration. However, when accounting for the increase in surface area associated with the bumped plates, heat transfer was universally improved. Heat transfer was found to be quadratically related to Re and z/d and exponentially related to x/d. Spent air flow had minimal effect on heat transfer except for the x/d=12 configuration. Discharge coefficients were found to be either unaffected or only marginally affected by plate geometry. Cd was found to be independent of z/d for z/d greater than or equal to 2. Although Re and x/d have an effect on Cd, there is no clear relationship between these parameters. Overall, a jet array with x/d=6.6 and z/d=5 impinging directly on every other bump of the hemispherical target plate produced the greatest improvement in heat transfer over the baseline smooth plate, but at the expense of slightly lower Cd values. Overall, jet impingement on bumped surfaces provides an improvement in heat transfer with a small decrease in Cd.
Download or read book An Investigation of Flow Interactions and Heat Transfer Characteristics for Single Jet Impingement on Rotating Disks written by Lee Dwight Grochowsky and published by . This book was released on 1975 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulent Flows and Heat Transfer written by Chia-Ch'iao Lin and published by Princeton University Press. This book was released on 2015-12-08 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume V of the High Speed Aerodynamics and Jet Propulsion series. Topics include transition from laminar to turbulent flow; turbulent flow; statistical theories of turbulence; conduction of heat; convective heat transfer and friction in flow of liquids; convective heat transfer in gases; cooling by protective fluid films; physical basis of thermal radiation; and engineering calculations of radiant heat exchange. Originally published in 1959. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.
Download or read book A Fundamental Investigation of Jet Impingement Heat Transfer written by Frederick F. Cadek and published by . This book was released on 1968 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluid thermal structural Study of Aerodynamically Heated Leading Edges written by and published by . This book was released on 1988 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Detailed Investigation of the Fluid Dynamics and Heat Transfer Related to Injection from a Compound Angled Shaped Film Cooling Hole written by Shane Haydt and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas turbines are used around the world to provide thrust for airplanes and to generate electricity. Designers and operators are constantly chasing higher thermal efficiency, and even an incremental increase is considered an achievement. Higher thermal efficiency begets higher turbine inlet temperatures, and the parts that are exposed to these temperatures require sophisticated cooling technologies. One such cooling method is shaped film cooling, which ejects low momentum coolant with the goal of it staying attached to the wall, spreading laterally, and providing a lower driving temperature for convection.In some film cooling manufacturing processes, the meter and diffuser are created in separate steps with separate machines, and an offset can occur in that process. A study was designed to quantify the change in adiabatic effectiveness for five offset directions: fore, fore-left, left, aft-left, and aft. All offset directions caused a detriment to film cooling performance, except for the fore offset, which improved adiabatic effectiveness relative to a no offset case. CFD helped show that the fore offset created a separation in the region of the film cooling metering section where jetting occurs, which decreased the high momentum and made the cooling jet more likely to remain attached to the surface. This study resulted in a patent.A large range of area ratios and blowing ratios were examined in a study designed to isolate the effect of area ratio by lengthening the diffuser of a shaped hole. Very high area ratios were generated that resulted in significant cooling potential. It was shown that at each area ratio there is an optimal blowing ratio beyond which the effectiveness will decrease or plateau. This was reduced to an optimal effective blowing ratio, M/AR, which was shown through CFD to be the condition when the coolant jet core has similar velocity magnitude to the mainstream flow. This results in a weak shear layer and a weak counter-rotating vortex pair.In an axially oriented hole, the mainstream flows over the top of a cooling jet and around the sides, in equal measure, creating a symmetric flowfield. In a compound angled shaped hole, the mainstream flows primarily around the leeward side, creating a strong shear layer and an asymmetric streamwise vortex. Compound angled shaped holes are used commonly in gas turbines, but there has been no work examining the adiabatic effectiveness and heat transfer coefficient augmentation at a range of compound angles, and there are no flowfield measurements. A comprehensive study of the flowfield, cooling effectiveness, and heat transfer coefficient were obtained for compound angled shaped holes for compound angles ranging from 0-60 in 15 increments. It is shown that asymmetry and vorticity magnitude increase with increasing compound angle and increasing blowing ratio. Holes with high compound angles can maintain jet attachment at high blowing ratios because the streamwise component of blowing ratio is reduced, which leads to high effectiveness. The most important contribution of this work was showing that the streamwise vortex increases heat transfer coefficient in a region adjacent to the jet, where very little coolant coverage exists. For this reason, compound angled shaped holes can cause local regions of increased heat flux relative to an uncooled surface, which may be an issue for some designs if not properly accounted for. Heat transfer coefficient augmentation increases as compound angle and blowing ratio increase. Designs that promote jet interaction, such as holes with a smaller pitchwise spacing or holes with significant lateral motion, cover the entire endwall in coolant and lessen the negative effects of high heat transfer coefficient augmentation.
Download or read book Enhanced Impingement Heat Transfer Using a Self Oscillating Jet Impingement Nozzle Array written by Michael Mincen Heatly and published by . This book was released on 1995 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comparison of Measured and Calculated Turbulent Heat Transfer in a Uniform and Nonuniform Flow Field on the X 15 Upper Vertical Fin at Mach Numbers of 4 2 and 5 3 written by and published by . This book was released on 1965 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:
