Rectangular channels/tubes

Effectively what Barnett (B3) did was to confirm the validity of Eq. (18) using burn-out data for water in round tubes. Subsequently, Eq. (18) was applied to more extensive round-tube data (M3, Tl), to annuli (B6), rectangular channels (M3), and rod-bundle arrangements (M4), using simple mathematical expressions for A and C, and a consistently high accuracy was achieved. Details of the respective correlations obtained are given in Section VIII. 

D2. De Bortoli, R. A., Green, S. J., Le Tourneau, B. W., Troy, M., and Weiss, A., Forced convection heat transfer burnout studies for water in rectangular channels and round tubes at pressure above 500 psia, WAPD-188 (1958). 

M3. Macbeth, R. V., Burnout analysis. 4. Application of a local conditions hypothesis to world data for uniformly heated round tubes and rectangular channels, AEEW-R.267 (1963). 

From the visual studies on the flow patterns for circular, trapezoidal and rectangular channels it may be concluded that as the tube diameter decreases, transitions between flow regimes occur at different combinations of superficial gas and liquid velocities. 

D Tank diameter or tube diameter or height of rectangular channel Fr n d/g, Froude number... 

The special flow conditions in circular (capillaries, tubes) or rectangular channels cause very different stresses depending on the position of the particles in the flow cross section. With laminar flow, for example the following applies to velocity gradient (see e.g. [37]) ... 

DeBortoli, R. A., S. J. Green, B. W. LeTourneau, M. Troy, and A. Weiss, 1958, Forced Convection Heat Transfer Burnout Studies for Water in Rectangular Channels and Round Tubes at Pressures above 500 psia, USAEC Rep. WAPD-188, Pittsburgh, PA. (5)... 

Macbeth, R. V., 1963a, Burnout Analysis Pt. 2, The Basic Burnout Curve, UK Rep. AEEW-R-167 Pt. 3, The Low Velocity Burnout Regime, AEEW-R-222 Pt. 4, Application of Local Conditions Hypothesis to World Data for Uniformly Heated Round Tubes and Rectangular Channels, AEEW-R-267, UK AEEW, Winfrith, England. (5)... 

For mass transfer in two-component cocurrent two-phase flow, very little work seems to have been carried on in systems analogous to those for which pressure-drops have been measured, that is, in tubes, pipes, or rectangular channels. Only two publications dealing with vertical flow (V2, V3), and two concerned with horizontal flow (A5, S6), have appeared. 

Flow in a thin rectangular channel (Figure 4.2), such as that used in field-flow fractionation, can be treated in a manner similar to that used for cylindrical capillary tubes. If the drag at the edges of the channel is neglected (infinite parallel plate model), then the force balance expression (corresponding to Eq. 4.5 for capillary tubes) becomes... 

The fully established friction factor for turbulent flow of a viscoelastic fluid in a rectangular channel is dependent on the aspect ratio, the Reynolds number, and the Weissenberg number. As in the case of the circular tube, at small values of Ws, the friction factor decreases from the newtonian value. It continues to decrease with increasing values of Ws, ultimately reaching a lower asymptotic limit. This limiting friction factor may be calculated from the following equation ... 

The behavior of a viscoelastic fluid in turbulent flow in the hydrodynamic entrance region of a rectangular channel can be estimated by assuming that the circular tube results are applicable provided that the hydraulic diameter replaces the tube diameter. 

Although the rectangular channel data are somewhat higher (5 to 10 percent) than the circular tube correlation equations, it appears that the circular tube predictions may be used for engineering estimates of the asymptotic heat transfer for rectangular ducts having an aspect ratio of approximately 0.5 to 1.0. 

The Research Center Karlsruhe has conducted combustion test series with premixed stoichiometric hydrogen-air mixtures both in a 12 m long cylindrical tube of 0.35 m diameter and in a rectangular channel with 0.1 x 0.1 m cross section and 3 - 6 m length. Different... 

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