Heat transfer characteristics of single row of jets issuing from screw-thread nozzles impinging on a concave surface

Turbine blades are directly exposed to hot oncoming combustion gases, so their leading edges require effective cooling techniques. Here, we investigated the heat transfer characteristics in a concave duct with an array of impingement jets, including the effect of rotation. The concave duct was used to simulate the inner surface of the leading edge of a blade. The inner surface was cooled by the impingement array jet method. The jet Reynolds number (Re) based on the jet nozzle diameter was fixed at 3,000, and the ratio of the height to target surface (H/d) was set to 2.0. The injection holes (d = 5 mm) were positioned in a staggered pattern, and the rotation number was about 0.032. We focused on the effects of rotating position orientations. We investigated front, leading, and trailing orientations. Naphthalene sublimation method was used to determine the local heat/mass transfer distributions, and the flow pattern was obtained by numerical simulation. Crossflow in the jet arrays was generated by the spent air from the impingement jet. The crossflow changes the flow characteristics at the stagnation point along the streamwise direction on a concave surface. Rotation of the duct increased the flow mixing compared with the stationary case. The jet flow was deflected because of the Coriolis force in the leading and trailing orientations. However, in the front orientation, the heat transfer characteristics showed deflection in the clockwise direction in the developing flow away from the stagnation point. Overall, the averaged heat transfer values were enhanced in the rotating cases. The trailing orientation case showed the highest averaged heat transfer among all tested cases.

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Heat Transfer Characteristics of Endwall with A Single Row of Oblique Pin Fins.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.66.649_2426 ◽

2000 ◽

Vol 66 (649) ◽

pp. 2426-2434

Author(s):

Ryosuke MATSUMOTO ◽

Shinzo KIKKAWA ◽

Mamoru SENDA ◽

Masayuki SUZUKI

Keyword(s):

Heat Transfer ◽

Heat Transfer Characteristics ◽

Single Row ◽

Transfer Characteristics ◽

Pin Fins

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Heat Transfer From Combustion Gases to a Single Row of Closely Spaced Tubes in a Swirl Crossflow Stirling Engine Heater

Journal of Heat Transfer ◽

10.1115/1.3245068 ◽

1982 ◽

Vol 104 (1) ◽

pp. 55-61 ◽

Cited By ~ 3

Author(s):

C. P. Bankston ◽

L. H. Back

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Stirling Engine ◽

Operating Conditions ◽

Experimental Program ◽

Working Fluid ◽

Heat Transfer Characteristics ◽

Transfer Coefficients ◽

Single Row ◽

Transfer Characteristics

This paper describes an experimental program to determine the heat-transfer characteristics of a combustor and heat-exchanger system in a hybrid solar receiver which utilizes a Stirling engine. The system consists of a swirl combustor with a crossflow heat exchanger composed of a single row of 48 closely spaced curved tubes. In the present study, heat-transfer characteristics of the combustor/heat-exchanger system without a Stirling engine have been studied over a range of operating conditions and output levels using water as the working fluid. Non-dimensional heat-transfer coefficients based on total heat transfer have been obtained and are compared with available literature data. The results show significantly enhanced heat transfer for the present geometry and test conditions. Also, heat transfer along the length of the tubes is found to vary, the effect depending upon test condition.

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Numerical simulations and optimization of impinging jet configuration

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-01-2020-0053 ◽

2020 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Alankrita Singh ◽

Balaji Chakravarthy ◽

BVSSS Prasad

Keyword(s):

Heat Transfer ◽

Numerical Simulations ◽

Impinging Jet ◽

Forward Model ◽

Concave Surface ◽

Geometrical Parameters ◽

Heat Transfer Characteristics ◽

Curvature Ratio ◽

Content Type ◽

Transfer Characteristics

Purpose Numerical simulations are performed to determine the heat transfer characteristics of slot jet impingement of air on a concave surface. The purpose of this paper is to investigate the effect of protrusions on the heat transfer by placing semi-circular protrusions on the concave surface at several positions. After identifying appropriate locations where the heat transfer is a maximum, multiple protrusions are placed at desired locations on the plate. The gap ratio, curvature ratio (d/D) and the dimensions of the plate are varied so as to obtain heat transfer data. The curvature ratio is varied first, keeping the concave diameter (D) fixed followed by a fixed slot width (d). A surrogate model based on an artificial neural network is developed to determine optimum locations of the protrusions that maximize the heat transfer from the concave surface. Design/methodology/approach The scope and objectives of the present study are two-dimensional numerical simulations of the problem by considering all the geometrical parameters (H/d, dp, Re, θ) affecting heat transfer characteristics with the help of networking tool and numerical simulation. Development of a surrogate forward model with artificial neural networks (ANNs) with a view to explore the full parametric space. To quantitatively ascertain if protrusions hurt or help heat transfer for an impinging jet on a concave surface. Determination of the location of protrusions where higher heat transfer could be achieved by using exhaustive search with the surrogate model to replace the time consuming forward model. Findings A single protrusion has nearly no effect on the heat transfer. For a fixed diameter of concave surface, a smaller jet possesses high turbulence kinetic energy with greater heat transfer. ANN is a powerful tool to not only predict impingement heat transfer characteristics by considering multiple parameters but also to determine the optimum configuration from many thousands of candidate solutions. A maximum increase of 8 per cent in the heat transfer is obtained by the best configuration constituting of multiple protrusions, with respect to the baseline smooth configuration. Even this can be considered as marginal and so it can be concluded that first cut results for heat transfer for an impinging jet on a concave surface with protrusions can be obtained by geometrically modeling a much simpler plain concave surface without any significant loss of accuracy. Originality/value The heat transfer during impingement cooling depends on various geometrical parameters but, not all the pertinent parameters have been varied comprehensively in previous studies. It is known that a rough surface may improve or degrade the amount of heat transfer depending on their geometrical dimensions of the target and the rough geometry and the flow conditions. Furthermore, to the best of authors’ knowledge, scarce studies are available with inclusion of protrusions over a concave surface. The present study is devoted to development of a surrogate forward model with ANNs with a view to explore the full parametric space.

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