Circumferential mixing

Cera.mic, The ceramic substrate is made from a mixture of siUcon dioxide, talc, and kaolin to make the compound cordierite [12182-53-5]. Cordierite possesses a very low coefficient of thermal expansion and is thermal-shock resistant. The manufacturing process involves extmding the starting mixture (which is mixed with water and kneaded into a sort of dough) through a complex die to form the honeycomb stmcture. The extmded piece is dried and fired in a kiln to form the cordierite. The outside or circumferential dimension is formed by the die, and the length is cut later with a ceramic saw. 

Very often the differential rolling mills are used here two horizontal cylindrical rolls rotate at different circumferential speeds (the ratio of the speeds being 1.5-2 to 1). This uneven rotation produces a shearing action which facilitates mixing. The further processes of manufacture may vary. Usually the paste is subjected to a final rolling. 

The mixer comprises two adjacent screws rotating in one direction at the same speed. The meshed screws provide for self-cleaning of the machine. The foregoing mixer incorporates sectional screws made up of screw bushes and mixing discs, which are circumferentially displayed relative to one another. 

The extruder is essentially a plug flow reactor. Although the material is being well mixed, this mixing is primarily in the radial and circumferential directions rather than axially. Due to the extreme conditions in the extruder, solids can liquefy, resulting in heterogeneous operation. 

Choi, D.K. and Choi. D.H., Dual Solution for Mixed Convection in a Horizontal Tube under Circumferentially Non-Uniform Heating . Int. J. Heat and Mass Transfer. Vol. 35, pp. 2053-2056, 1992. 

Chou, Fu Chu, Laminar Mixed Convection in the Thermal Entrance Region of Horizontal Rectangular Channels with Uniform Heat Input Axially and Uniform Wall Temperature Circumferentially , Canadian J. Chem. Eng., Vol. 68. pp. 577-584.1990. 

Longitudinal cracks Circumferential cracks Mixed orientation... 

Certain circumferential temperature differences exist on FFB regenerator from the bottom to the top. The temperature of two catalyst streams entering at the diagonal entrances may differ by as much as 200°C, resulting in a 20 to 50°C measured circumferential bed temperature difference at different elevations. The two curves in Fig. 9 show the axial temperature distribution on two sides of a commercial FFB unit with d, 5 m from 3 m upward from the bottom, indicating a circumferential temperature difference of 20°C, which is evidence of reduced mixing. 

It 15 highly necessary to keep sufficient oxygen concentration across the combustor through better mixing in the circumferential direction. 

P circumferential heat flux dimensionless group for internal mixed convection... 

Laser Dopple Velocity (LDV) measurements in the venturi premix duct outlet therefore were carried out. These tests, which were run at cold conditions at the design point with the same Reynolds number, show a very symmetric and even velocity profile at all circumferential angles in the duct outlet. The measured RMS values, 30-35% of the mean velocity, also showed that a high turbulence level exists in the venturi. This will enhance the mixing and fuel vaporization process. 

A section of the tube with the inner surface covered by a mixed black/brown scale is shown in Figure 5.68. Circumferential cracks growing in a zigzag fashion... 

The metering section of the screw controls the extruder output. It should contain 100% melt at a nearly constant temperature. Only the velocity components parallel to the flight (Fig. 5.10a) contribute to the output the other two velocity components are part of a circulatory flow that mixes the polymer. The output is a combination of a drag flow and a pressure flow. The drag flow is due to the motion of the screw surface with circumferential velocity... 

The IHX is a vertical, counter current flow, shell and tube heat exchanger (fig. 6). Each IHX has 3000 straight tubes (19 mm OD x 0.8 mm WT) with primary sodium on shell side and secondary sodium on the tube side. The tubes are arranged in circumferential pitch. A variable flow distribution is provided inside the IHX tubes with a higher flow on the outer rows to improve the thermohydraulic behaviour of the tube bundle. A mixing device is also provided at the secondary outlet to reduce the temperature differences between inner and outer shell of the secondary outlet header. Absence of flow induced vibration of tube bundle and the drain pipe in the downcomer have been verified by theoretical analysis. 

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