Analysis of experimental data on heat and mass transfer in a boundary layer

Boyarshinov, B. F.

doi:10.1007/bf02672819

Cited by 8 publications

(5 citation statements)

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“…including those obtained at Tu0 = 18-26%, there are sections with St,t ~ Re~ ~ on tile experimental deI)endences. The stratification of" curves is described by the formula Std = ~p0.332 Re~ ~ Sc -~ where ~p = 1.2.3 ..... A similar effect was reported in [7]. The Re~ numbers at which the transition from one level to anotimr occurs vary not only with the height of the obstacle but also with the turbulence level.…”

Section: (X/m)t-~176mentioning

confidence: 68%

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Some characteristics of heat and mass transfer in a turbulent air flow over a surface

Boyarshinov¹

2000

J Appl Mech Tech Phys

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536.244It is shown that, for" a certain proportion between the rib height (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) In diffusional combustion of a condensed filel, tile intensity of heat-and mass-transfer processes can be controlled by deliberate variatioxl of the fluctuating characteristics of the reacting boundary layer. Its stability to flameout can be achieved by installing gas-dynamic obstacles. Theoretical studies of a turbulent boundary layer with local separation fiwe computational difficulties caused by the complex character of the flow [1,2]. A large body of empirical information accunmlated in tests without combustion [3] shows that the rates of heat and mass transfer behind an obstacle can significantly increase. However, there are differences in reported estimates Of the dimensions of reattaehment and relaxation flow regions and also in determined intensities of the transfer processes and their description. For a reacting boundary layer, no experinlental data are availal)le.The objective of the present work was to experinlentally study mass transfer during vai)orization of a liquid tiM (ethanol) behind ribs of wtrious heights for various turbulence levels of air streams with and without combustion.Experimental Setup and Measurement Procedure. The tests were conducted in an open-type wind tunnel described in [4]. At tim inIet of the confuser, a wire grid with a t x 1 ram-mesh or a grating with 25 threaded holes M27 x 1.5 (with a 43-ram gap between the hole centers) was installed. The confilser of length x0 = 300 mm (contoured according to Vitoshinskii's formula; contraction ratio 1 : 6.8) joiimd the test section 100 x 100 ram. There was no upper wall of the channel, the side walls were transparent, and the 1)ottom wall was made of perforate(l plates (stainless steel). The length of the first plate was 40 mm, and that of the other six plates wr 80 ram. A rib of height h = 0-15 mm was installed at the test-section entrance, across the entire width of the channel. The turbulence level Tu0 = 8, 18, or 26% was regulated by the number of oI)en holes in the grating (25, 9, or 5, respectively); the turbulence level in tests with tlm grid was Tu0 = 1%. These vahles were fi)un(l by averaging the nleasurement results over 81 points of the entrance section spaced 10 nml apart. The measurements were performed with the help of a DISA hot-wire anemometer (single-wire probe, wire diameter 8 Itm, 55M01 bridge and 55D10 linearizer). The unifbrnlity of the air stream at the channel entrance decreased with increasing degree of turbulence, an(1 tile inaxinmnl deviation from the average (across tile channel) value of tile flow velocity reached +14% for Tu0 = 26%.

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Section: (X/m)t-~176mentioning

confidence: 68%

“…This increase corresponds to tile transition from the level qlp = 2 to the le~l qJj, = 3. The dependence for the boundary-layer mass transfer with ethanol combustion [7] Std = ~p0.41 Re~ ~ is shown in Fig. 2b.…”

Section: (X/m)t-~176mentioning

confidence: 98%

Some characteristics of heat and mass transfer in a turbulent air flow over a surface

Boyarshinov¹

2000

J Appl Mech Tech Phys

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“…A model of the flow behind a recirculation zone was proposed in [1] to explain the scatter of experimental data with stratified inten- sity of heat and mass transfer. This model is based on the assumption of possible secondary separations and reattachments of the flow.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

“…Investigations of transfer processes under complicated conditions [1] showed that an anomalous increase in the burning rate can be observed during combustion in the boundary layer. Elevated turbulence and acceleration of the main flow cause a twofold or threefold local increase in heat-and mass-transfer intensity.…”

Section: Introductionmentioning

confidence: 98%

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Distribution of OH and CH Radicals in the Boundary Layer with Ethanol Combustion

Boyarshinov

Titkov

Fedorov

2005

Combust Explos Shock Waves

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The influence of free-stream turbulence on the distributions of CH and OH radicals is studied with the use of optical methods of measurements in focused beams. The data on CH concentration are obtained for the minimum level of turbulence, and the OH concentration profiles are obtained for three levels of velocity fluctuations: 1, 8, and 18%. It is shown that the regions where the OH and CH radicals are observed in the laminar boundary layer are shifted from the temperature maximum toward the oxidizer zone and toward the fuel zone, respectively. The highest level of the OH concentration is close to values typical of hydrogen combustion. The root-meansquare fluctuations of velocity and the mean values of the OH concentration vary nonmonotonically along the flame.

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