The Influence of the Recirculation Region: A Comparison of the Convective Heat Transfer Downstream of a Backward-Facing Step and Behind a Jet in a Cross Flow

Scherer, Viktor; Wittig, Sigmar

doi:10.1115/89-gt-59

Cited by 3 publications

(5 citation statements)

References 14 publications

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“…Figure 5 shows the excellent agreement of the present data with the values of Vogel and Eaton (1985) and Scherer and Wittig (1989). The experiments of Vogel and Eaton have been carried out under constant heat flux conditions, whereas we in our earlier study used a constant wall temperature technique.…”

Section: Backward-lacing Stepsupporting

confidence: 72%

“…Although considerable progress has been made in the numerical description of convective heat transfer in turbulent flows (Scherer et al, 1988;Scherer and Wittig, 1989;Waschka et al, 1991), fundamental experimental work is still of major interest: only detailed and accurate experimental data allow the improvement of numerical codes and the development of better physical models for the description of the transport processes of thermal convection.…”

Section: Introductionmentioning

confidence: 99%

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Thermographic heat transfer measurements in separated flows

Scherer

Wittig

Bittlinger

et al. 1993

Experiments in Fluids

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Abstract.A measurement technique to determine the surface heat transfer distribution in complex turbulent flows is described. For this purpose, a constant wall heat flux test surface has been designed. To measure the surface temperature of the test plate, an infrared camera was used. The instrumentation allows the determination of the heat transfer with high accuracy and detailed spatial resolution. In examining combustor-type separated flow, the capabilities of the technique are demonstrated and its accuracy is verified by appropriate conventional techniques.

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Section: Backward-lacing Stepsupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Thermographic heat transfer measurements in separated flows

Scherer

Wittig

Bittlinger

et al. 1993

Experiments in Fluids

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“…In the present context, the mixing flow patterns as found in gas turbine combustors are of interest. In a sequence of earlier studies in our institute, the flow and heat transfer characteristics downstream of a two-dimensional jet and behind a backward-facing step have been analysed Wittig, 1989, Wittig andScherer, 1987). In continuation of these investigations, the present study is directed towards the heat transfer downstream of a row of three-dimensional jets entering a crossflow employing the thermographic technique described earlier (Scherer et al, 1988, Wittig, 1990).…”

Section: Introductionmentioning

confidence: 94%

Jets in a Crossflow: Effects of Hole Spacing to Diameter Ratio on the Spatial Distribution of Heat Transfer

Scherer

Wittig

Morad

et al. 1991

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration

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Detailed measurements of local heat transfer coefficients are presented for air injection through a row of holes into a crossflow. Pitch-to-diameter ratios of 2,4, and 6 are realized and the momentum flux ratio is varied in the range from 0.25 to 4.0. The injection angle of the jets is fixed at 90°. The experimental technique developed uses an Infrared Camera to measure the temperature distribution on the constant heat flux test surface. This measurement technique allows detailed spatial resolution of the heat transfer and gives information about the three-dimensional mixing process of the jets with the mainstream. The experimental results indicate a large influence of the hole spacing to diameter ratio, (s/d), on the heat transfer coefficient. With s/d = 2.0, the spanwise heat transfer coefficients in the vicinity of the injection holes are noticed to be highly uniform. For momentum flux ratios, J, greater than 1, two regions of high heat transfer coefficient exist. The first region occurs in the vicinity of the injection holes. The second region observed some distance downstream is due to the reattachment of the jets to the surface.

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“…Recently, convective heat-transfer performance downstream of a backward-facing step was investigated by Scherer and Wittig (1989). The reattachment length predicted with the k-e model was underestimated by about 10% to 20%.…”

Section: Backward-facing Stepsmentioning

confidence: 99%

“…The reattachment length predicted with the k-e model was underestimated by about 10% to 20%. The main conclusion of Scherer and Wittig (1989) was that the two-layer wall-function approach of Chieng and Launder (1980) was superior to the standard wall functions.…”

Section: Backward-facing Stepsmentioning

confidence: 99%

Influence of Prandtl number and effects of disruption shape on the performance of enhanced tubes with the separation and reattachment mechanism

B¹,

J²

1992

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The pressure-drop and heat-transfer performance of an enhanced tube with transverse disruptions can be predicted with a numerical modeling method, an accomplishment not previously achieved. Two computer codes wet,*,employed to achieve this goal n an orthogonal code and a nonorthogonal, body-fitted code. The turbulence closure was achieved with a two-layer turbulence model. The orthogonal computer code was used to determine the influence of the Prandtl number. The numerical simulations demonstrated that six distinct regions exist and that three zones dominate the thermal performance. The nonorthogonal, body-fitted numerical code was used to determine the thermohydraulic performance of enhanced tubes with transverse, periodic sine-, semicircle-, arc-, and trapezoidshaped disruptions. The research showed that there was a trade-off between the heat-transfer and pressure-drop performances when the disruption shape becomes more contoured, and that the local heat transfer is strongly dependent on the shape in the vicinity of the disruption, but it is less dependent in the downstream recirculation region and in the boundary-layer development zone. SummaryNumerical analysis was successfully used to evaluate the single-phase thermal-hydraulic performance of internally enhanced heat-exchanger tubes. A two-dimensional, axisymmetric flow field was selected because it is an accurate representation for the internal geometry considered in this investigation (two-dimensional transverse disruptions or ribs). The flow field was considered to be fully developed because the tube length is much larger than the tube diameter for typical heat exchangers. Both laminar and turbulent flow were considered, although the work discussed in this report focuses on the more important turbulent case.Very good agreement was obtained between the predicted friction factors and mean heattransfer coefficients and the corresponding measured values. For this validation, five tube geometries with rectangular disruptions (Webb et al. 1971), two tube geometries with arc-shaped disruptions , and one tube with a semicircular disruption (Nunner 1956)'* The helixangle is definedas the angle betweenthe centerlineof thetube and the disruption.The helixanglesof transversedisruptionsand longitudinal disruptionsare90' and 0°, respectively.

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The Influence of the Recirculation Region: A Comparison of the Convective Heat Transfer Downstream of a Backward-Facing Step and Behind a Jet in a Cross Flow

Cited by 3 publications

References 14 publications

Thermographic heat transfer measurements in separated flows

Thermographic heat transfer measurements in separated flows

Jets in a Crossflow: Effects of Hole Spacing to Diameter Ratio on the Spatial Distribution of Heat Transfer

Influence of Prandtl number and effects of disruption shape on the performance of enhanced tubes with the separation and reattachment mechanism

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