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Shital Yashwant Waware, Sandeep Sadashiv Kore i Suhas Prakashrao Patil. "Heat Transfer Enhancement in Tubular Heat Exchanger with Jet Impingement: A Review". Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 101, nr 2 (20.01.2023): 8–25. http://dx.doi.org/10.37934/arfmts.101.2.825.
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Heat exchanger (HE) is a thermal device used to transfer heat from higher fluid temperatures to lower fluid temperatures. There is an increasing need to increase the efficiency of HEs, develop a wide range of investigations to increase heat transfer rate (HTR), and reduce the size and cost of industrial apparatus in accordance. The current work's goal is to review articles that discuss the main types of tubular heat HEs, factors that affect HTR, and jet impingement in tubular HEs, which are considered among the equipment used in various industries. Researchers have proposed several models of tubular HEs. Many industrial processes, cooling technology, refrigeration equipment, sustainable energy applications, and other fields use tubular HEs. Jet impingement cooling is assumed to be a very efficient method for increasing HT rate, and it has many uses in both the scientific and industrial spheres. This paper's goal is to present an overview of various techniques for improving HT in relation to jet impingement cooling and to define the area of potential future research. This study focuses on a variety of experimental and numerical studies to examine the HT and hydrodynamic behaviour of jet impingement over a range of Reynolds numbers, target surface shapes, distances from the jet plate or nozzle to the target plate, extended jet holes, and the use of nanofluids. Both single jet and multiple jet impingements cooling are included in the current work. The summary of jet impingement for various applications keeps the spotlight on new methods for enhancing HT.
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Su, Zhong-Gen, Wei Zheng i Zhen-Dong Zhang. "Study on diesel cylinder-head cooling using nanofluid coolant with jet impingement". Thermal Science 19, nr 6 (2015): 2025–37. http://dx.doi.org/10.2298/tsci140509118z.
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To improve the heat-transfer performance of a diesel-engine cylinder head, nanofluid coolant as a new fluid was investigated, and jet impingement technology was then used to study on how to better improve heat-transfer coefficient at the nose bridge area in the diesel-engine cylinder head. Computational fluid dynamic simulation and experiments results demonstrated that using the same jet impingement parameters, the different volume shares of nanofluids showed better cooling effect than traditional coolant, but the good effect of the new cooling method was unsuitable for high volume share of nanofluid. At the same volume share of nanofluid, different jet impingement parameters such as jet angles showed different heat-transfer performance. This result implies that a strong association exists between jet impingement parameters and heat-transfer coefficient. The increase in coolant viscosity of the nanofluid coolant using jet impingement requires the expense of more drive-power cost.
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Qiu, Shuxia, Peng Xu, Liping Geng, Arun Mujumdar, Zhouting Jiang i Jinghua Yang. "Enhanced heat transfer characteristics of conjugated air jet impingement on a finned heat sink". Thermal Science 21, nr 1 Part A (2017): 279–88. http://dx.doi.org/10.2298/tsci141229030q.
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Air jet impingement is one of the effective cooling techniques employed in micro-electronic industry. To enhance the heat transfer performance, a cooling system with air jet impingement on a finned heat sink is evaluated via the computational fluid dynamics method. A two-dimensional confined slot air impinging on a finned flat plate is modeled. The numerical model is validated by comparison of the computed Nusselt number distribution on the impingement target with published experimental results. The flow characteristics and heat transfer performance of jet impingement on both of smooth and finned heat sinks are compared. It is observed that jet impingement over finned target plate improves the cooling performance significantly. A dimensionless heat transfer enhancement factor is introduced to quantify the effect of jet flow Reynolds number on the finned surface. The effect of rectangular fin dimensions on impingement heat transfer rate is discussed in order to optimize the cooling system. Also, the computed flow and thermal fields of the air impingement system are examined to explore the physical mechanisms for heat transfer enhancement.
4
Popiel, C. O., i L. Boguslawski. "Local Heat Transfer From a Rotating Disk in an Impinging Round Jet". Journal of Heat Transfer 108, nr 2 (1.05.1986): 357–64. http://dx.doi.org/10.1115/1.3246929.
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The results of an experimental investigation of local convective heat transfer from the surface of a rotating disk in an impinging free round air jet, issuing from a long tube, are reported. Using a transient heat transfer method applied to the ring-shaped h-calorimeter (as a single lumped capacitance element) measurements of convective heat transfer rates were made for five impingement radius (fixed) to tube diameter ratios for a range of rotational and jet Reynolds numbers. In the pure impingement-dominated regime, where the rotation of the disk does not show an effect on heat transfer, the velocity ratio is ur/uj ≤ (1 − 2 × 10−4 Re2/3) (1 − 0.18 r/d), where ur = tangential velocity of the disk at the jet impingement radius r, uj = average exit velocity of jet, and d = jet tube diameter. In this regime, the local heat transfer on the rotating disk can be strongly enhanced by jet impingement. For ur/uj ⪞ 5, the effect of the jet impingement on heat transfer can be neglected. The discussion of the heat transfer results has been supported by smoke flow visualization.
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Hussain, Liaqat, Muhammad Mahabat Khan, Manzar Masud, Fawad Ahmed, Zabdur Rehman, Łukasz Amanowicz i Krzysztof Rajski. "Heat Transfer Augmentation through Different Jet Impingement Techniques: A State-of-the-Art Review". Energies 14, nr 20 (9.10.2021): 6458. http://dx.doi.org/10.3390/en14206458.
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Jet impingement is considered to be an effective technique to enhance the heat transfer rate, and it finds many applications in the scientific and industrial horizons. The objective of this paper is to summarize heat transfer enhancement through different jet impingement methods and provide a platform for identifying the scope for future work. This study reviews various experimental and numerical studies of jet impingement methods for thermal-hydraulic improvement of heat transfer surfaces. The jet impingement methods considered in the present work include shapes of the target surface, the jet/nozzle–target surface distance, extended jet holes, nanofluids, and the use of phase change materials (PCMs). The present work also includes both single-jet and multiple-jet impingement studies for different industrial applications.
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Wang, Longfei, Fengbo Wen, Songtao Wang, Xun Zhou i Zhongqi Wang. "Application and Design of Multi-Impingement Cooling Channel in Turbine Blade Trail Edge". International Journal of Turbo & Jet-Engines 37, nr 3 (27.08.2020): 241–56. http://dx.doi.org/10.1515/tjj-2017-0023.
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AbstractThe numerical simulations are used to conduct the comparative study of pin-fins cooling channel and multi-impingement cooling channel on the heat transfer and flow, and to design the multi-impingement channel through the parameters of impinging distance and impingement-jet-plate thickness. The Reynolds number ranges from 1e4 to 6e4. The dimensionless impinging distance is 0.60, 1.68, 2.76, respectively, and the dimensionless impinging-jet-thickness is 0.5, 1.0, 1.5, respectively. The endwall surface, pin-fins surface, impinging-jet-plate surface are the three object surfaces to investigate the channel heat transfer performance. The heat transfer coefficient $h$ and augmentation factor $Nu/N{u_0}$ are selected to measure the surface heat transfer, and the friction coefficient $f$ is chosen to evaluate the channel flow characteristics. The impinging-jet-plate surface owns higher heat transfer coefficient and larger area than pin-fins surface, which are the main reasons to improve the heat transfer performance of multi-impingement cooling channel. Reducing the impinging distance can improve the endwall surface heat transfer obviously and enhance impingement plate surface heat transfer to some extent, decreasing the thickness of impinging-jet-plate can significantly increase its own heat transfer coefficient, which both all increase the cooling air flow loss.
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Tang, Tsz Loong, Hamidon Salleh, Muhammad Imran Sadiq, Mohd Anas Mohd Sabri, Meor Iqram Meor Ahmad i Wan Aizon W. Ghopa. "Experimental and Numerical Investigation of Flow Structure and Heat Transfer Behavior of Multiple Jet Impingement Using MgO-Water Nanofluids". Materials 16, nr 11 (25.05.2023): 3942. http://dx.doi.org/10.3390/ma16113942.
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Nanofluids have attracted significant attention from researchers due to their ability to significantly enhance heat transfer, especially in jet impingement flows, which can improve their cooling performance. However, there is a lack of research on the use of nanofluids in multiple jet impingements, both in terms of experimental and numerical studies. Therefore, further investigation is necessary to fully understand the potential benefits and limitations of using nanofluids in this type of cooling system. Thus, an experimental and numerical investigation was performed to study the flow structure and heat transfer behavior of multiple jet impingement using MgO-water nanofluids with a 3 × 3 inline jet array at a nozzle-to-plate distance of 3 mm. The jet spacing was set to 3, 4.5, and 6 mm; the Reynolds number varies from 1000 to 10,000; and the particle volume fraction ranges from 0% to 0.15%. A 3D numerical analysis using ANSYS Fluent with SST k-ω turbulent model was presented. The single-phase model is adopted to predict the thermal physical nanofluid. The flow field and temperature distribution were investigated. Experimental results show that a nanofluid can provide a heat transfer enhancement at a small jet-to-jet spacing using a high particle volume fraction under a low Reynolds number; otherwise, an adverse effect on heat transfer may occur. The numerical results show that the single-phase model can predict the heat transfer trend of multiple jet impingement using nanofluids correctly but with significant deviation from experimental results because it cannot capture the effect of nanoparticles.
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Cooper, L. Y. "Heat Transfer in Compartment Fires Near Regions of Ceiling-Jet Impingement on a Wall". Journal of Heat Transfer 111, nr 2 (1.05.1989): 455–60. http://dx.doi.org/10.1115/1.3250698.
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The problem of heat transfer to walls from fire-plume-driven ceiling jets during compartment fires is introduced. Estimates are obtained for the mass, momentum, and enthalpy flux of the ceiling jet immediately upstream of the ceiling–wall junction. An analogy is drawn between the flow dynamics and heat transfer at ceiling-jet/wall impingement and at the line impingement of a wall and a two-dimensional, plane, free jet. Using the analogy, results from the literature on plane, free-jet flows and corresponding wall-stagnation heat transfer rates are recast into a ceiling-jet/wall-impingement-problem formulation. This leads to a readily usable estimate for the heat transfer from the ceiling jet as it turns downward and begins its initial descent as a negatively buoyant flow along the compartment walls. Available data from a reduced-scale experiment provide some limited verification of the heat transfer estimate. Depending on the proximity of a wall to the point of plume–ceiling impingement, the result indicates that for typical full-scale compartment fires with energy release rates in the range 200–2000 kW and fire-to-ceiling distances of 2–3 m, the rate of heat transfer to walls can be enhanced by a factor of 1.1–2.3 over the heat transfer to ceilings immediately upstream of ceiling-jet impingement.
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Zhou, Li Ming, Lei Zhu, Jing Quan Zhao i Meng Zheng. "Numerical Simulation Study of Impinging Jet Impact Fin Surface on Heat Transfer Characteristics". Advanced Materials Research 663 (luty 2013): 586–91. http://dx.doi.org/10.4028/www.scientific.net/amr.663.586.
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Three-dimensional numerical simulation was implemented to analyze the heat transfer characteristics for jet impingement impact fin surface. 60 calculation cases were simulated to investigate the effects of different fin surfaces on heat transfer characteristics, and 12 jet array impingement cases were calculated for comparison. The results shown that the fin shape, the height and the fin arrangement were the critical factors to affect the jet impingement and the best combination were existed in a certain range. The thermal resistance of cylinder fin arranged in order was34.7 percent higher than that of cylinder fin arranged staggered. The thermal resistance of square fin arranged in order was38.9 percent higher than that of square fin arranged staggered .The heat transfer coefficients of impinging jet impact fin surface were better than that of jet array impingement. The fitting correlations on heat transfer of impinging jet impact fin surface were given.
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Travnicek, Z., F. Marsik i T. Hyhlik. "SYNTHETIC JET IMPINGEMENT HEAT/MASS TRANSFER". Journal of Flow Visualization and Image Processing 13, nr 1 (2006): 67–76. http://dx.doi.org/10.1615/jflowvisimageproc.v13.i1.50.
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Wolf, D. H., F. P. Incropera i R. Viskanta. "Local jet impingement boiling heat transfer". International Journal of Heat and Mass Transfer 39, nr 7 (maj 1996): 1395–406. http://dx.doi.org/10.1016/0017-9310(95)00216-2.
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Azevedo, L. F. A., B. W. Webb i M. Queiroz. "Pulsed air jet impingement heat transfer". Experimental Thermal and Fluid Science 8, nr 3 (kwiecień 1994): 206–13. http://dx.doi.org/10.1016/0894-1777(94)90049-3.
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Liewkongsataporn, W., T. Patterson i F. Ahrens. "Pulsating Jet Impingement Heat Transfer Enhancement". Drying Technology 26, nr 4 (26.03.2008): 433–42. http://dx.doi.org/10.1080/07373930801929268.
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Yutaka, Oda, i Takeishi Kenichiro. "1179 ENHANCEMENT OF JET IMPINGEMENT HEAT TRANSFER WITH RIB TURBULATORS IN WALL JET REGION". Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2013.4 (2013): _1179–1_—_1179–6_. http://dx.doi.org/10.1299/jsmeicjwsf.2013.4._1179-1_.
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Zhang, Jing Zhou, Xiao Ming Tan, Bo Liu i Xing Dan Zhu. "Investigation for Convective Heat Transfer on Grinding Work-Piece Surface Subjected to a Mist/Air Impinging Jet". Applied Mechanics and Materials 249-250 (grudzień 2012): 434–42. http://dx.doi.org/10.4028/www.scientific.net/amm.249-250.434.
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Two objectives were outlined in the current study. The first objective aimed to assess the detailed flow and heat transfer features in the vicinity of a rotating grinding wheel with jet impingement directed at grinding zone by numerical investigation. The second objective aimed to assess the quantitative evaluation for heat transfer enhancement on a grinding work-piece surface subjected to the mist/air jet impingement by experimental investigation. The results show that the coupled action of swirl air entrainment and jet impingement is benefit somewhat for overall convective heat transfer in relative to stationary disk case whether the disk rotates in clockwise or contrary clockwise. When the jet impinging direction is consistent with the rotational direction of rotating disk, convective heat transfer enhancement is achieved near grinding region, especially at higher rotating speed. Furthermore, the increasing of water droplet in mist/air jet impingement showed significant enhancement of the cooling effect.
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Hsieh, Shou-Shing, Jung-Tai Huang i Huang-Hsiu Tsai. "Heat Transfer of Confined Circular Jet Impingement". Journal of Mechanics 17, nr 1 (marzec 2001): 29–38. http://dx.doi.org/10.1017/s1727719100002392.
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ABSTRACTExperiments for heat transfer characteristics of confined circular single jet impingement were conducted. The effect of jet Reynolds number, jet hole-to-plate spacing and heat flux levels on heat transfer characteristics of the heated target surface was examined and presented. The local heat transfer coefficient along the surface is measured and correlations of the stagnation point, local and average Nusselt number are developed and discussed. Finally, comparisons of the present data with existing results were also made.
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Vu, Duc Manh. "THE EFFECT OF JET NOZZLE DIAMETER ON HEAT TRANSFER COEFFICIENT IN AN IMPINGEMENT CROSS FLOW SYSTEM". Journal of Science and Technique 15, nr 3 (1.07.2020): 5–16. http://dx.doi.org/10.56651/lqdtu.jst.v15.n03.112.
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Jet impingement is one of effective methods adopted to enhance the local heat transfer coefficient between cooling air stream andblades. For the impingement created by multi-holes located in the blade midchord region orthe leading edge, the jet nozzle diameter D of impingement tubes is one of the parameters having significantly effects on the heat exchange coefficient. The paper uses ANSYS-CFX software to simulate the heat exchange characteristics of 3 multi-hole impingement tube taking into account the velocity ratio of jet flow and cross flow (VR = 3, 5, 7): 4 holes (2×2) with diameter D = 0.75mm, 9 holes (3×3) D=0.5mm, 25 holes (5×5) D = 0.3mm. The results showed that the smaller the jet diameter is, the more significant influence the cross flow has influence on the heat transfer coefficient, and a diameter of D=0.5mm yields the highest heat transfer coefficient.
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Mohr, J. W., J. Seyed-Yagoobi i R. H. Page. "Heat Transfer Characteristics of a Radial Jet Reattachment Flame". Journal of Heat Transfer 119, nr 2 (1.05.1997): 258–64. http://dx.doi.org/10.1115/1.2824218.
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A Radial Jet Reattachment Combustion (RJRC) nozzle forces primary combustion air to exit radially from the combustion nozzle and to mix with gaseous fuel in a highly turbulent recirculation region generated between the combustion nozzle and impingement surface. High convective heat transfer properties and improved fuel/ air mixing characterize this external mixing combustor for use in impingement flame heating processes. To understand the heat transfer characteristics of this new innovative practical RJRC nozzle, statistical design and analysis of experiments was utilized. A regression model was developed which allowed for determination of the total heat transfer to the impingement surface as well as the NOx emission index over a wide variety of operating conditions. In addition, spatially resolved flame temperatures and impingement surface temperature and heat flux profiles enabled determination of the extent of the combustion process with regards to the impingement surface. Specifically, the relative sizes of the reaction envelope, high temperature reaction zone, and low temperature recirculation zone were all determined. At the impingement surface in the reattachment zone very high local heat flux values were measured. This study provides the first detailed local heat transfer characteristics for the RJRC nozzle.
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Gudi, Abhay, i Vijaykumar Hindasageri. "Novel Method to Improve Heat Transfer Rate Through Delta Swirl Tape for a Swirl Jet Impingement Study". International Journal of Heat and Technology 40, nr 3 (30.06.2022): 715–21. http://dx.doi.org/10.18280/ijht.400308.
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With advancement of electronic equipment’s, there is a need to have an efficient method or mechanism that helps remove heat from the system. Air jet impingement is generally implied method for effective heat removal from these equipment’s. There are several types of air jet impingement techniques used and among them swirl air jet is one of most prominent and proven method. In this study, a novel method is proposed to improve heat transfer of a swirling air jet impingement. Experimental study has been performed with swirl tape and novel delta tape having twist ratio (T.R) = 2 for jet to plate distance of z/d=2 to 8 and Re varying between 1500 to 9000. This study is basically carried out to improve the heat transfer at low Re conditions. Thermal imaging technique is used to derive centerline Nu values for different jet to plate distances (z/d=2 to 8). Study shows that novel delta tape adds significant improvement in heat transfer for above mentioned conditions.
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Sun, Run Peng, Wei Bing Zhu, Hong Chen i Chang Jiang Chen. "Numerical Study on Flow and Heat Transfer Characteristics of Jet Impingement Cooling". Applied Mechanics and Materials 148-149 (grudzień 2011): 680–83. http://dx.doi.org/10.4028/www.scientific.net/amm.148-149.680.
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Three-dimensional numerical study is conducted to investigate the heat transfer characteristics for the flow impingement cooling in the narrow passage based on cooling technology of turbine blade.The effects of the jet Reynolds number, impingement distance and initial cross-flow on heat transfer characteristic are investigated.Results show that when other parameters remain unchanged local heat transfer coefficient increases with increase of jet Reynolds number；overall heat transfer effect is reduced by initial cross-flow；there is an optimal distance to the best effect of heat transfer.
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Wu, Pey Shey, Chia Yu Hsieh i Shen Ta Tsai. "Heat Transfer Enhancement of Jet Impingement on a Flat Plate Attached by a Porous Medium with a Center Cavity". Defect and Diffusion Forum 297-301 (kwiecień 2010): 427–32. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.427.
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Jet impingement heat transfer on a target plate covered with a thick porous layer with or without a cylindrical center cavity is experimentally investigated using the transient liquid crystal technique. Based on the results of jet impingement on a bare flat plate, heat transfer enhancement due to the attachment of porous medium is assessed. The varying parameters in the experiments include the nozzle-to-plate distance, jet Reynolds number, jet-to-cavity diameter ratio, and the cavity depth. Results of Nusselt number distribution, stagnation-zone Nusselt number, and averaged Nusselt number over a region of 3 times the hole diameter are documented. Experimental results show that the attachment of the porous layer with a center cavity can either hamper, or effectively enhance the jet impingement heat transfer over a flat plate. The maximum enhancement occurs at jet Reynolds number of 12400 when the cavity is a through hole and the cavity has the same diameter as the jet. The stagnation-zone Nusselt number increases 58.3% and the averaged Nusselt number increases 77.5% at the maximum enhancement condition. On the other hand, the addition of the thick porous layer without a center cavity gave rise to severe adverse effect on jet impingement heat transfer.
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Yang, Xing, Hang Wu i Zhenping Feng. "Jet Impingement Heat Transfer Characteristics with Variable Extended Jet Holes under Strong Crossflow Conditions". Aerospace 9, nr 1 (15.01.2022): 44. http://dx.doi.org/10.3390/aerospace9010044.
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In this paper, detailed flow patterns and heat transfer characteristics of a jet impingement system with extended jet holes are experimentally and numerically studied. The jet holes in the jet plate present an inline array of 16 × 5 rows in the streamwise (i.e., the crossflow direction) and spanwise directions, where the streamwise and spanwise distances between adjacent holes, which are normalized by the jet hole diameter (xn/d and yn/d), are 8 and 5, respectively. The jets impinge onto a smooth target plate with a normalized distance (zn/d) of 3.5 apart from the jet plate. The jet holes are extended by inserting stainless tubes throughout the jet holes and the extended lengths are varied in a range of 1.0d–2.5d, depending on the jet position in the streamwise direction. The experimental data is obtained by using the transient thermochromic liquid crystal (TLC) technique for wide operating jet Reynolds numbers of (1.0 × 104)–(3.0 × 104). The numerical simulations are well-validated using the experimental data and provide further insight into the flow physics within the jet impingement system. Comparisons with a traditional baseline jet impingement scheme show that the extended jet holes generate much higher local heat transfer levels and provide more uniform heat transfer distributions over the target plate, resulting in the highest improvement of approximately 36% in the Nusselt number. Although the extended jet hole configuration requires a higher pumping power to drive the flow through the impingement system, the gain of heat transfer prevails over the penalty of flow losses. At the same pumping power consumption, the extended jet hole design also has more than 10% higher heat transfer than the baseline scheme.
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Xiao, K., J. He i Z. Feng. "Effects of alternating elliptical chamber on jet impingement heat transfer in vane leading edge under different cross-flow conditions". Aeronautical Journal 125, nr 1291 (30.04.2021): 1484–500. http://dx.doi.org/10.1017/aer.2021.31.
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ABSTRACTThis paper proposes an alternating elliptical impingement chamber in the leading edge of a gas turbine to restrain the cross flow and enhance the heat transfer, and investigates the detailed flow and heat transfer characteristics. The chamber consists of straight sections and transition sections. Numerical simulations are performed by solving the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes (RANS) equations with the Shear Stress Transport (SST) k– $\omega$ turbulence model. The influences of alternating the cross section on the impingement flow and heat transfer of the chamber are studied by comparison with a smooth semi-elliptical impingement chamber at a cross-flow Velocity Ratio (VR) of 0.2 and Temperature Ratio (TR) of 1.00 in the primary study. Then, the effects of the cross-flow VR and TR are further investigated. The results reveal that, in the semi-elliptical impingement chamber, the impingement jet is deflected by the cross flow and the heat transfer performance is degraded. However, in the alternating elliptical chamber, the cross flow is transformed to a pair of longitudinal vortices, and the flow direction at the centre of the cross section is parallel to the impingement jet, thus improving the jet penetration ability and enhancing the impingement heat transfer. In addition, the heat transfer in the semi-elliptical chamber degrades rapidly away from the stagnation region, while the longitudinal vortices enhance the heat transfer further, making the heat transfer coefficient distribution more uniform. The Nusselt number decreases with increase of VR and TR for both the semi-elliptical chamber and the alternating elliptical chamber. The alternating elliptical chamber enhances the heat transfer and moves the stagnation point up for all VR and TR, and the heat transfer enhancement is more obvious at high cross-flow velocity ratio.
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SU, Lo May, Shyy Woei CHANG i Shyr Fuu CHIOU. "Impingement Heat Transfer of Reciprocating Jet Array". JSME International Journal Series B 46, nr 3 (2003): 434–50. http://dx.doi.org/10.1299/jsmeb.46.434.
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Herrero Martin, R., i J. M. Buchlin. "Jet impingement heat transfer from lobed nozzles". International Journal of Thermal Sciences 50, nr 7 (lipiec 2011): 1199–206. http://dx.doi.org/10.1016/j.ijthermalsci.2011.02.017.
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Nontula, Thantup, Natthaporn Kaewchoothong, Wacharin Kaew-apichai i Chayut Nuntadusit. "Effect of Rotation Number on Heat Transfer Characteristics of a Row of Impinging Jets in Confined Channel". Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 77, nr 1 (7.11.2020): 161–71. http://dx.doi.org/10.37934/arfmts.77.1.161171.
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Jet impingement has been applied for internal cooling in gas turbine blades. In this study, heat transfer characteristics of impinging jets from a row of circular orifices were investigated inside a flow channel with rotations. The Reynolds number (Re) based on the jet mean velocity was fixed at 6,700. Whereas, the rotation number (Ro) of a channel was varied from 0 to 0.0099. The jet-to-impingement distance ratio (L/Dj) and jet pitch ratio (P/Dj) were respective 2 and 4, Dj is a jet diameter of 5 mm. The thermochromic liquid crystals (TLCs) technique was used to measure the heat transfer coefficient distributions on an impingement surface. The results show that heat transfer enhancement on a jet impingement surface depended on the effects of crossflow and Coriolis force. The local Nusselt number at X/Dj?20 on the leading side (LS) was higher than on the trailing side (TS) while heat transfer on the LS at 20?X/Dj?40 gained the lowest, compared to on the TS. The average Nusselt number ratios ( ) on the TS at Ro = 0.0049 gave higher than on the LS of around 2.17%. On the other hand, the on the TS at Ro = 0.0099 was less than the LS of about 0.08%.
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Garimella, Suresh V., i Vincent P. Schroeder. "Local Heat Transfer Distributions in Confined Multiple Air Jet Impingement". Journal of Electronic Packaging 123, nr 3 (26.12.2000): 165–72. http://dx.doi.org/10.1115/1.1371923.
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Heat transfer from a discrete heat source to multiple, normally impinging, confined air jets was experimentally investigated. The jets issued from short, square-edged orifices with still-developing velocity profiles on to a foil heat source which produced a constant heat flux. The orifice plate and the surface containing the heat source were mounted opposite each other in a parallel-plates arrangement to effect radial outflow of the spent fluid. The local surface temperature was measured in fine increments over the entire heat source. Experiments were conducted for different jet Reynolds numbers (5000<Re<20,000), orifice-to-target spacing 0.5<H/d<4, and multiple-orifice arrangements. The results are compared to those previously obtained for single air jets. A reduction in orifice-to-target spacing was found to increase the heat transfer coefficient in multiple jets, with this effect being stronger at the higher Reynolds numbers. With a nine-jet arrangement, the heat transfer to the central jet was higher than for a corresponding single jet. For a four-jet arrangement, however, each jet was found to have stagnation-region heat transfer coefficients that were comparable to the single-jet values. The effectiveness of single and multiple jets in removing heat from a given heat source is compared at a fixed total flow rate. Predictive correlations are proposed for single and multiple jet impingement heat transfer.
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Zuckerman, Neil, i Noam Lior. "Impingement Heat Transfer: Correlations and Numerical Modeling". Journal of Heat Transfer 127, nr 5 (1.05.2005): 544–52. http://dx.doi.org/10.1115/1.1861921.
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Uses of impinging jet devices for heat transfer are described, with a focus on cooling applications within turbine systems. Numerical simulation techniques and results are described, and the relative strengths and drawbacks of the k-ε,k-ω, Reynolds stress model, algebraic stress models, shear stress transport, and v2f turbulence models for impinging jet flow and heat transfer are compared. Select model equations are provided as well as quantitative assessments of model errors and judgments of model suitability.
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Carozzo, Giovanni, Carlo Cravero, Martino Marini i Matteo Mazza. "CFD Simulation of a Temperature Control System for Galvanizing Line of Metal Band Based on Jet Cooling Heat Transfer". Applied Sciences 10, nr 15 (30.07.2020): 5248. http://dx.doi.org/10.3390/app10155248.
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The work focuses on the development of a thermo-fluid dynamic simulation model of a section of close cooling, called a jet cooler, inserted in the galvanizing line of metal band production. Two models of increasing accuracy have been tested and calibrated by experimental data. Special attention to turbulence modeling and boundary conditions has been given. A literature survey was focused on the jet impingement process (the reference heat transfer mechanism for the system component) and on available correlations to predict the heat exchange coefficient. The numerical simulation of jet impingement has been applied to a module of an actual industrial cooler for steel band production. The operation of the jet cooler was simulated in real operating conditions to get a detailed insight into the jet impingement mechanism in order to optimize the heat transfer and reduce, as far as possible, the cooling fluid mass flow rate. The comparison of heat transfer correlations, used in industrial preliminary design, with detailed CFD results is discussed.
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Kuznetsov, V. V., A. S. Shamirzaev i A. S. Mordovskoy. "Prospects for using two-phase micro-size systems for high heat flux removal". Journal of Physics: Conference Series 2057, nr 1 (1.10.2021): 012058. http://dx.doi.org/10.1088/1742-6596/2057/1/012058.
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Abstract Heat transfer in active systems for high heat removal based on the micro-channels and hybrid micro-channel/micro-jet is considered. The application of these systems allows significantly increasing the critical heat flux for a dense arrangement of the heat stressed equipment. The characteristics of heat transfer and critical heat flux during subcooled flow boiling of water in the micro-channel heat sink and during micro-jet impingement in narrow channel are obtained. The experiments are performed for the horizontal segmented microchannels with a cross section of 340×2000 μm2 made on the top of copper target and for impingement micro-jet cooling of the copper target in the gap of 1000 μm. It has been found that, compared with impingement micro-jet cooling in similar condition, the micro-channel cooling is more effective for high heat flux removal although it creates the considerably high wall temperature.
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Hollworth, B. R., i L. R. Gero. "Entrainment Effects on Impingement Heat Transfer: Part II—Local Heat Transfer Measurements". Journal of Heat Transfer 107, nr 4 (1.11.1985): 910–15. http://dx.doi.org/10.1115/1.3247520.
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Convective heat transfer was measured for a heated axisymmetric air jet impinging on a flat surface. It was found that the local heat transfer coefficient does not depend explicitly upon the temperature mismatch between the jet fluid and the ambient fluid if the convection coefficient is defined in terms of the difference between the local recovery temperature and target surface temperature. In fact, profiles of local heat transfer coefficients defined in this manner were found to be identical to those measured for isothermal impinging jets.
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Kura, Tomasz, Elżbieta Fornalik-Wajs, Jan Wajs i Sasa Kenjeres. "Heat transfer intensification by jet impingement – numerical analysis using RANS approach". E3S Web of Conferences 108 (2019): 01025. http://dx.doi.org/10.1051/e3sconf/201910801025.
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Jet impingement is a method of the heat transfer enhancement applied in the engineering systems. The idea is to generate fast-flow fluid jet which impinge on the heated (or cooled) surface, causing significantly higher heat transfer rate. Although some flat surface jet impingement cases are described in the literature, the validated data is still limited. The reason is coming from the fact, that these flows are hydrodynamically complex. Therefore the numerical analysis is necessary to understand the phenomena, especially in the range of turbulent flow. The well-known and accurate method is Reynolds Averaged Navier-Stokes (RANS) approach. However, depending on the applied turbulence model, various results can be obtained. The reason is that the jet impingement strongly depends on the complex boundary layer effects and their resolving is still challenging for RANS models and until now it is their weakest point. In the paper, the hydrodynamic and thermal, numerical results of jet impingement are presented, depending on selected RANS based models. The aim was to indicate their ability to anticipate the turbulence parameters.
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Dutta, Rabijit, Anupam Dewan i Balaji Srinivasan. "CFD study of slot jet impingement heat transfer with nanofluids". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 230, nr 2 (20.04.2015): 206–20. http://dx.doi.org/10.1177/0954406215583521.
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We present a numerical investigation of hydrodynamic and heat transfer behaviors for Al2O3–water nanofluids for laminar and turbulent confined slot jets impingement heat transfer at nanoparticle volume fractions of 3% and 6%. A comparison of the nanofluid with the base fluid has been performed for the same Reynolds number and same jet inlet velocity. A single-phase fluid approach was used to model the nanofluid. Further, the thermo-physical properties of nanofluid were calculated using a recent approach. For the same value of Reynolds number, maximum increase in the average heat transfer coefficient at the impingement plate was found to be approximately 27% and 22% for laminar and turbulent slot impingements, respectively, for 6% volume fraction of nanofluid as compared to that of water. However, the pumping power curve showed a steep increase with the volume fraction with nearly five times increase in the pumping power observed for 6% volume fraction nanofluid. Further, the energy-based performance was assessed with the help of the performance evaluation criterion (PEC). PEC values indicate that nanofluids do not necessarily represent the most efficient coolants for this type of application. Moreover, at the same jet inlet velocity, a reduction in the heat transfer coefficient of 7% and 20% was observed for nanofluid as compared to base fluid for laminar and turbulent flows, respectively.
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Kanokjaruvijit, Koonlaya, i Ricardo F. Martinez-Botas. "Parametric Effects on Heat Transfer of Impingement on Dimpled Surface". Journal of Turbomachinery 127, nr 2 (1.04.2005): 287–96. http://dx.doi.org/10.1115/1.1791292.
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Jet impingement on a dimpled surface is investigated experimentally for Reynolds numbers in the range 5000–11500, and jet-to-plate spacing from 1 to 12 jet-diameters. These include spatially resolved local Nusselt numbers with impingement both on the dimpled itself and on the flat portion between dimples. Two dimple geometries are considered: hemispherical dimples and double or cusp elliptical dimples. All experiments were carried under maximum crossflow that is the spent air exits along one way. At the narrow jet-to-plate spacing such as H/Dj=2, a vigorous recirculation occurred, which prevented the dimpled plate to enhance heat transfer. The effect of impinging jet positions meant that impinging onto dimples generated more and higher energetic vortices, and this led to better heat transfer performance. Cusped elliptical dimples increase the heat transfer compared to a flat plate less than the hemispherical geometry. The influence of dimple depth was also considered, the shallower dimple, d/Dd=0.15, improves significantly the heat transfer by 64% compared to that of the flat surface impingement at H/Dj=4; this result was 38% higher than that for a deeper dimple of d/Dd=0.25. The very significant increase in average heat transfer makes dimple surface impingement a candidate for cooling applications. Detailed pressure measurements will form a second part of this paper, however, plenum pressure measurements are illustrated here as well as a surface pressure measurement on both streamwise and spanwise directions.
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Takeishi, Ken-Ichiro, Robert Krewinkel, Yutaka Oda i Yuichi Ichikawa. "Heat Transfer Enhancement of Impingement Cooling by Adopting Circular-Ribs or Vortex Generators in the Wall Jet Region of A Round Impingement Jet". International Journal of Turbomachinery, Propulsion and Power 5, nr 3 (7.07.2020): 17. http://dx.doi.org/10.3390/ijtpp5030017.
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In the near future, when designing and using Double Wall Airfoils, which will be manufactured by 3D printers, the positional relationship between the impingement cooling nozzle and the heat transfer enhancement ribs on the target plate naturally becomes more accurate. Taking these circumstances into account, an experimental study was conducted to enhance the heat transfer of the wall jet region of a round impingement jet cooling system. This was done by installing circular ribs or vortex generators (VGs) in the impingement cooling wall jet region. The local heat transfer coefficient was measured using the naphthalene sublimation method, which utilizes the analogy between heat and mass transfer. As a result, it was clarified that, within the ranges of geometries and Reynolds numbers at which the experiments were conducted, it is possible to improve the averaged Nusselt number Nu up to 21% for circular ribs and up to 51% for VGs.
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Tang, Zhiguo, Hai Li, Feng Zhang, Xiaoteng Min i Jianping Cheng. "Numerical study of liquid jet impingement flow and heat transfer of a cone heat sink". International Journal of Numerical Methods for Heat & Fluid Flow 29, nr 11 (4.11.2019): 4074–92. http://dx.doi.org/10.1108/hff-08-2018-0451.
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Purpose The purpose of this paper is to explore the flow and heat transfer characteristics of the jet impingement onto a conical heat sink and evaluate the ability of heat transfer enhancement. Design/methodology/approach A numerical study of the flow and heat transfer of liquid impingement on cone heat sinks was conducted, and transition SST turbulence model was validated and adopted. The flow and thermal performances were investigated with the Reynolds number that ranges from 5,000 to 23,000 and cone angle that ranges from 0° to 70° in four regions. Findings Local Nusselt numbers are large, and pressure coefficients drop rapidly near the stagnation point. In the conical bottom edge, a secondary inclined jet was observed, thereby introducing a horseshoe vortex that causes drastic fluctuations in the curves of the flow and heat transfer. The average Nusselt numbers are higher in a conical protuberance than in flat plates in most cases, thus indicating that the heat transfer performance of jet impingement can be improved by a cone heat sink. The maximum increase is 13.6 per cent when the cone angle is 60°, and the Reynolds number is 23,000. Originality/value The flow and heat transfer behavior at the bottom edge of the cone heat sink is supplemented. The average heat transfer capacity of different heat transfer radii was evaluated, which provided a basis for the study of cone arrays.
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Kumar, Deepak, Mohammad Zunaid i Samsher Gautam. "Thermal Performance Exploration of Air Foil Shape of Pillars using Impinging Jet in Heat Sink". Tobacco Regulatory Science 7, nr 5 (30.09.2021): 2794–807. http://dx.doi.org/10.18001/trs.7.5.1.48.
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Objectives: The current investigation introduces the concept of heat sink with combination of jet impingement, micro – channel and air foil shaped pillars. A numerical model is designed to explore the thermal performance of jet impingement with constant heat flux. The steady state conditions are assumed for the laminar and incompressible flow. For the purpose of study dimensionless variables are formed. The performance of jet impingement was predicted in terms of different parameters like temperature rise, drop in pressure and coefficient of heat transfer. Augmentation in pitch diameter ratio, leads to increase in temperature for a particular value of height diameter ratio. Also the heat transfer coefficient gets lowered with the increase in pitch diameter ratio. So proper selection of dimensionless parameters to increase the heat dissipation is of utmost importance.
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Muthukannan, M., M. Brajesh, P. Rajeshkanna, S. Jeyakuma i N. Vikneswaran. "Experimental Investigation of Heat Transfer of Single Jet Impingement on a Aluminium Block". Advanced Materials Research 984-985 (lipiec 2014): 1115–24. http://dx.doi.org/10.4028/www.scientific.net/amr.984-985.1115.
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Jet Impingement is used in many applications where extensive heating (or) cooling is necessary to produce high heat transfer rate in a localized region. Those applications include glass production, drying of papers, annealing of metals and cooling of electronic equipments. Present work is involved with the experimental investigation of single jet impingement on Aluminium block. The effect of Reynolds number and the distance between the jet and block (H/d ratio) are considered as the interesting variable parameters. The heat transfer rate and reattachment length are reported in detailed for the various Reynolds number and various jet to block ratio. The flow physics revealed that when the Reynolds number increases the reattachment length also increases. The heat transfer rate increases with increase in Reynolds number up to critical heat flux and then further increase of Reynolds number leads to decrease in heat transfer.
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Seyed-Yagoobi, J., V. Narayanan i R. H. Page. "Comparison of Heat Transfer Characteristics of Radial Jet Reattachment Nozzle to In-Line Impinging Jet Nozzle". Journal of Heat Transfer 120, nr 2 (1.05.1998): 335–41. http://dx.doi.org/10.1115/1.2824253.
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The heat transfer characteristics of three submerged radial jet reattachment (RJR) nozzles with exit angles of +45, 0, and −10 deg are compared to the heat transfer characteristics of a conventional submerged in-line jet (ILJ) nozzle. The nozzles are compared at their favorable spacing from the impingement surface. The comparisons are based on two criteria: (1) identical fluid flow power, and (2) identical peak pressure exerted on the impingement surface. The local and area-averaged Nusselt numbers are presented. Experiments were conducted for two different flow power conditions. Comparison under identical flow power indicates that significant enhancements in local and comparable enhancements in area-averaged Nusselt numbers can be achieved with the RJR nozzles over the conventional ILJ nozzle while being able to control the net force exerted on the impingement surface. The comparison between the ILJ and RJR nozzles on the basis of the same peak pressure exerted on the impingement surface indicates that the zero degree exit angle RJR nozzle heat transfer characteristics are superior to the ILJ nozzle.
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Garimella, S. V., i R. A. Rice. "Confined and Submerged Liquid Jet Impingement Heat Transfer". Journal of Heat Transfer 117, nr 4 (1.11.1995): 871–77. http://dx.doi.org/10.1115/1.2836304.
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The local heat transfer from a small heat source to a normally impinging, axisymmetric, and submerged liquid jet, in confined and unconfined configurations, was experimentally investigated. A single jet of FC-77 issuing from a round nozzle impinged onto a square foil heater, which dissipated a constant heat flux. The nozzle and the heat source were both mounted in large round plates to ensure axisymmetric radial outflow of the spent fluid. The local surface temperature of the heat source was measured at different radial locations (r/d) from the center of the jet in fine increments. Results for the local heat transfer coefficient distribution at the heat source are presented as functions of nozzle diameter (0.79 ≤ d ≤ 6.35 mm), Reynolds number (4000 to 23,000), and nozzle-to-heat source spacing (1 ≤ Z/d ≤ 14). Secondary peaks in the local heat transfer observed at r/d ≈ 2 were more pronounced at the smaller (confined) spacings and larger nozzle diameters for a given Reynolds number, and shifted radially outward from the stagnation point as the spacing increased. The secondary-peak magnitude increased with Reynolds number, and was higher than the stagnation value in some instances. Correlations are proposed for the stagnation and average Nusselt numbers as functions of these parameters.
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ZHANG, Lixi, Gaopan CAO i Zhengyang ZHANG. "Numerical simulation on heat transfer and entropy generation of impingement cooling on boss shaped surface". Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 40, nr 2 (kwiecień 2022): 296–305. http://dx.doi.org/10.1051/jnwpu/20224020296.
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Using impingement jet to cool the external cavity of the end wall of the gas turbine guide blade is very effective for prolonging the service life of the gas turbine and ensuring its safety operation. In this paper, the numerical simulation method is used to study the impingement cooling heat transfer performance of the boss shaped surface in the external cavity of the end wall of the gas turbine guide blade, and the entropy generation of the impingement heat transfer process is analyzed. The results show that the average Nusselt number on the impingement target surface and the impingement hole surface increase with the increase of the Reynolds number of the impingement jet. When the Reynolds number is constant, the average Nusselt number of impingement target surface and impingement hole surface decrease with the increase of impingement target distance, but the cooling range on the impingement target surface increases and the heat transfer is more uniform. With the increase of the width of the boss shaped upper surface, the cooling range on the impingement target surface relatively decreases, and the average Nusselt numbers of the impingement target surface decreases and that of the impingement hole surface increases respectively. The heat transfer of the upper surface of the boss is better than that of the lower surface on both sides. The entropy generation in the process of impingement cooling mainly comes from the entropy production caused by viscous dissipation and the entropy flow caused by heat transfer. The entropy production in the flow vortex region is the main reason for the entropy generation. The research conclusions can provide basis and reference for optimizing the structural and operating parameters of boss shaped impingement cavity and improving its impingement heat transfer effect.
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Uysal, U., P. W. Li, M. K. Chyu i F. J. Cunha. "Heat Transfer on Internal Surfaces of a Duct Subjected to Impingement of a Jet Array with Varying Jet Hole-Size and Spacing". Journal of Turbomachinery 128, nr 1 (1.02.2005): 158–65. http://dx.doi.org/10.1115/1.2101859.
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One significant issue concerning the impingement heat transfer with a jet array is related to the so-called “crossflow,” where a local jet performance is influenced by the convection of the confluence from the impingement of the jet∕jets placed upstream. As a result, the heat transfer coefficient may vary along the streamwise direction and creates more or less nonuniform cooling over the component, which is undesirable from both the performance and durability standpoints. Described in this paper is an experimental investigation of the heat transfer coefficient on surfaces impinged by an array of six inline circular jets with their diameters increased monotically along the streamwise direction. The local heat transfer distributions on both the target surface and jet-issuing plate are measured using a transient liquid crystal technique. By varying the jet hole-size in a systematic manner, the actual distribution of jet flow rate and momentum within a jet array may be optimally metered and controlled against crossflow. The effects on the heat transfer coefficient distribution due to variations of jet-to-target distance and interjet spacing are investigated. The varying-diameter results are compared with those from a corresponding array of uniform jet diameter.
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Kumar, M., i D. Mukhopadhyay. "Heat transfer characterization under radial jet and falling film induced rewetting". Kerntechnik 86, nr 5 (1.10.2021): 325–37. http://dx.doi.org/10.1515/kern-2021-0013.
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Abstract Empirical correlations are developed for rewetting velocity and maximum heat transfer coefficient during rewetting phase of single hot vertical Fuel Pin Simulator (FPS) by using radial jet impingement and falling film. Emergency Core Cooling System (ECCS) has been designed for Advance Heavy water Reactor (AHWR) to rewet the hot fuel pin under the loss of coolant accident. Coolant injection takes place from a water rod which is located at the center of the fuel bundle in form of jets to rewet hot surface of fuel pin under loss of coolant accident. This kind of design to reflood the fuel bundle is different than bottom and top spray reflooding practiced in PWR and BWR type of nuclear reactors. There are two different kinds of rewetting found during radial jet induced cooling. The first one is due to radial jet impingement and the second one is due to falling film which is below the jet impingement point. Rewetting velocity has been predicted along the length of fuel pin due to radial jet impingement cooling. Temperature of FPS has been varied from 400°C to 700°C with help of different powers supply, simulating decay heat of reactor. A variation of coolant radial jet mass flow rate is from 0.5 lpm to 1.8 lpm. It is considered during ECCS injection. It has been observed from the experiments that rewetting velocity decreases with increasing the clad surface temperature and increases with increasing the coolant mass flow rate. The rewetting velocity in falling film is found to be nearly 1.8 times higher than rewetting velocity predicted in circumferential direction. Further, it is found that maximum heat transfer coefficient increases with increasing the radial jet coolant mass flow rate. The maximum heat transfer coefficient in case of radial jet impingement is found to be nearly 1.5 times the falling film rewetting. Developed correlation predicts the maximum heat transfer coefficient with experimental data well within the error band of ±10%.
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Sparrow, E. M., Z. X. Xu i L. F. A. Azevedo. "Heat (Mass) Transfer for Circular Jet Impingement on a Confined Disk With Annular Collection of the Spent Air". Journal of Heat Transfer 109, nr 2 (1.05.1987): 329–35. http://dx.doi.org/10.1115/1.3248084.
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Heat (mass) transfer experiments have been performed for a single circular jet impinging perpendicular to a confined disk, with the spent air being collected in an annulus which surrounds the jet delivery tube. This configuration provides precise control of the surface area affected by the impinging jet and also assures complete collection of the spent air. During the course of the experiments, parametric variations were made of the dimensionless separation distance between the jet origin and the impingement disk, of the ratio of disk diameter to the jet diameter, and of the Reynolds number. It was found that the heat (mass) transfer coefficient at the impingement surface increased substantially with a decrease in the jet diameter. Furthermore, for the smaller diameter jet, there was an optimum separation distance at which a maximum value of the heat (mass) transfer coefficient was achieved. For a jet of larger diameter, the transfer coefficient decreased monotonically as the separation distance increased.
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Chambers, Andrew C., David R. H. Gillespie, Peter T. Ireland i Geoffrey M. Dailey. "The Effect of Initial Cross Flow on the Cooling Performance of a Narrow Impingement Channel". Journal of Heat Transfer 127, nr 4 (30.03.2005): 358–65. http://dx.doi.org/10.1115/1.1800493.
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Impingement channels are often used in turbine blade cooling configurations. This paper examines the heat transfer performance of a typical integrally cast impingement channel. Detailed heat transfer coefficient distributions on all heat transfer surfaces were obtained in a series of low temperature experiments carried out in a large-scale model of a turbine cooling system using liquid crystal techniques. All experiments were performed on a model of a 19-hole, low aspect ratio impingement channel. The effect of flow introduced at the inlet to the channel on the impingement heat transfer within the channel was investigated. A novel test technique has been applied to determine the effect of the initial cross flow on jet penetration. The experiments were performed at an engine representative Reynolds number of 20,000 and examined the effect of additional initial cross flow up to 10 percent of the total mass flow. It was shown that initial cross flow strongly influenced the heat transfer performance with just 10 percent initial cross flow able to reduce the mean target plate jet effectiveness by 57 percent.
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Dutta, Sandip, i Prashant Singh. "Opportunities in Jet-Impingement Cooling for Gas-Turbine Engines". Energies 14, nr 20 (13.10.2021): 6587. http://dx.doi.org/10.3390/en14206587.
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Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand which of them are critical and how these heat-transfer-enhancement concepts work. The aim of this paper is to excite the thermal sciences community of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to innovative 3D printing technologies. However, the orifice shape variations show that it is hard to beat a sharp-edged round orifice in heat transfer coefficient, but it comes with a higher pressure drop across the orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number, thus giving the designer some control over thermal budgeting of a component. Reduction in crossflow has been attempted with channel modifications. The use of high-porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion is provided in the conclusion.
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Gao, Ming-Xin, Jian Yang, Yue Zhang i Hua Song. "Investigation of the transient heat transfer to a supersonic air jet impinging on a high-temperature plate based on a discrimination-experiment method". PLOS ONE 17, nr 3 (14.03.2022): e0264968. http://dx.doi.org/10.1371/journal.pone.0264968.
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A discrimination-experiment method is developed to investigate the transient heat transfer of air jet impingement by discretizing the solid domain into mutually adiabatic test cylinders. This method can not only reduce the influence of the transverse heat transfer of a solid domain on the heat transfer characteristics of the jet but can also simplify the two-dimensional or three-dimensional heat conduction problem into a one-dimensional problem. Moreover, the discrimination-experiment method eliminates the embedment of thermocouples into the solid domains, further improving the accuracy and reliability of the proposed method. The transient heat transfer characteristics of a supersonic air jet impinging on a high-temperature target (860°C) and the effects of thermo physical parameters, such as the density, specific heat capacity, thermal conductivity and nozzle-to-target distance (H/D = 3, 4, and 5) are analyzed in detail using the discrimination-experiment method. The results provide important guidance for the thermal design of supersonic air jet impingement.
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Chester, N. L., Mary A. Wells, V. Prodanovic i Matthias Militzer. "Transient Cooling of a Hot Steel Plate by an Inclined Bottom Jet". Advanced Materials Research 15-17 (luty 2006): 738–43. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.738.
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Controlled cooling on the runout table is a crucial component in the production of highly tailored steels since it has a strong influence on the final mechanical properties. High efficiency heat transfer in impinging jet cooling makes this an important method for heat transfer enhancement. The purpose of this study is to develop an experimental database for modelling of boiling heat transfer for bottom jet impingement that occurs during runout table cooling in a steel mill. Experiments have been carried out on a pilot scale runout table using stationary plates, with focus on the effect of water flow rate and nozzle inclination to the overall heat transfer rates. Volumetric flow rates and inclination angles are in the range of 35-55 l/min and 0-30º, respectively. Temperatures on the test plates are measured internally very close to the surface during cooling for the purpose of reducing thermal lag and receiving better data responsiveness. These measurements are taken at the impingement point and several streamwise distances from the impingement point. From the above measurements transient cooling data on the hot steel plate by bottom jet impingement has been analysed.
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Wang, X. S., Z. Dagan i L. M. Jiji. "Prediction of Surface Temperature and Heat Flux of a Microelectronic Chip With Jet Impingement Cooling". Journal of Electronic Packaging 112, nr 1 (1.03.1990): 57–62. http://dx.doi.org/10.1115/1.2904342.
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In this paper, a previously developed analytic solution is applied to the conjugate heat transfer problem of jet impingement cooling of a microelectronic chip. The analysis is used to predict the surface temperature and heat flux distributions of a chip cooled by a laminar impinging FC-77 liquid or water jet with uniform heat flux dissipation at the heated bottom of the chip. Results are presented for two jet diameters of 0.5 and 1 mm. It is shown that, for a constant Reynolds number, the surface temperature is lower when the jet diameter is smaller. On the other hand, when the jet diameter is increased, the surface temperature and heat flux distributions are more uniform. Water jet impingement cooling shows much lower surface temperature and much higher heat transfer coefficient than FC-77 jet cooling. The thermal resistance for FC-77 liquid jet is 6 times larger than that for a water jet.
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Mohaghegh, Mohammad Reza, Syeda Humaira Tasnim, Amir A. Aliabadi i Shohel Mahmud. "Jet Impingement Cooling Enhanced with Nano-Encapsulated PCM". Energies 15, nr 3 (29.01.2022): 1034. http://dx.doi.org/10.3390/en15031034.
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In the present study, the laminar flow and heat transfer of water jet impingement enhanced with nano-encapsulated phase change material (NEPCM) slurry on a hot plate is analytically investigated for the first time. A similarity solution approach is applied to momentum and energy equations in order to determine the flow velocity and heat transfer fields. The effect of different physical parameters such as jet velocity, Reynolds number, jet inlet temperature, and the NEPCM concentration on the cooling performance of the impinging jet are investigated. The volume fraction of NEPCM particles plays an essential role in the flow and heat transfer fields. The results show that NEPCM slurry can significantly enhance the cooling performance of the system as it improves the latent heat storage capacity of the liquid jet. However, the maximum cooling performance of the system is achieved under an optimum NEPCM concentration (15%). A further increase in NEPCM volume fraction has an unfavorable effect due to increasing the viscosity and reducing the conductivity simultaneously. The effect of adding nano-metal particles on the heat transfer performance is also investigated and compared with NEPCM slurry. NEPCM slurry shows a better result in its maximum performance. Compared with the water jet, adding nano and NEPCM particles would overall enhance the system’s thermal performance by 16% and 7%, respectively.