T-junctions

When a signal reaches a T junction it splits into two copies of itself, one copy traveling along each path. Whenever a 7-0 signal reaches the end of its data path, the path is extended by one site. 

The experimental data obtained in conventional size channels and micro-channels with diameters between 100 pm and 6.0 mm are examined to further elucidate and understand the differences in two-phase flow characteristics between the microchannels and conventional size channels. Since two separate sets of experiments have been conducted using air and water in acrylic channels with diameters between 500 pm and 6.0 mm, and nitrogen gas-water in fused silica channels with diameters between 50 and 500 pm, the authors refer to the former channels as conventional size channels, and the latter channels as micro-channels for convenience. Two different inlet sections were covered in micro-channel experiments, a gradually reducing section and a T-junction. 

For a micro-channel connected to a 100 pm T-junction the Lockhart-Martinelli model correlated well with the data, however, different C-values were needed to correlate well with all the data for the conventional size channels. In contrast, when the 100 pm micro-channel was connected to a reducing inlet section, the data could be fit by a single value of C = 0.24, and no mass velocity effect could be observed. When the T-junction diameter was increased to 500 pm, the best-fit C-value for the 100 pm micro-channel again dropped to a value of 0.24. Thus, as in the void fraction data, the friction pressure drop data in micro-channels and conventional size channels are similar, but for micro-channels, significantly different data can be obtained depending on the inlet geometry. 

Kawahara et al. (2002) presented void fraction data obtained in a 100 pm micro-channel connected to a reducing inlet section and T-junction section. The superficial velocities are Uqs = 0.1-60m/s for gas, and fAs = 0.02-4 m/s for liquid. The void fraction data obtained with a T-junction inlet showed a linear relationship between the void fraction and volumetric quality, in agreement with the homogeneous model predictions. On the contrary, the void fraction data from the reducing section inlet experiments showed a non-linear void fraction-to-volumetric quality relationship ... 

This reactor comprises a single-channel reaction zone followed by a quenching (cooling) zone [72], Gases, pre-heated in a separate zone, are contacted in an T-junction and mixed in a short passage thereafter. Such mixed gases enter the above-mentioned reaction zone. 

Carrier-gas is transferred from the column through a heated metal capillary, which minimizes the dead volume at the end of the column and prevents condensation of the column effluent prior to its entry into the scrubbing unit. The tube carrying the liquid stream is joined to the gas stream tube, at a T-junction that is joined to the mixing coil by a glass-to-metal seal. Furfural is transferred from the gas stream into the liquid stream and the colour develops the two phases are then separated by the debubbling unit and the liquid stream is re-sampled through the flow cell of the colorimeter. A Technicon peristaltic... 

I raced along the straight to the T junction where I had first met my mysterious cat helper. I swung left around the comer and a lantern was uncovered right in my face, dazzling me. I stopped dead. 

Figure 6.20 Schematic diagram of a /tw/t-junction transistor and associated input and output voltage characteristics. Reprinted, by permission, from W. Callister, Materials Science and Engineering An Introduction, 5th ed., p. 633. Copyright 2000 by John Wiley Sons, Inc.

The mixing chamber is a T-junction having a 1-mm inside diameter and, as a result, the two liquid flows (process solution and sodium hydroxide solution) meet each other under a 90° angle. Subsequently, the mixed solution is sent to the detection cell (Fig. 5.17). The dimensions of the working electrode and auxiliary sensors are adjusted in such a way that they strongly decrease (ca. 50%) the internal volume actually taken in by the solution. The actual volume of the detection cell amounts to ca. 7 ml. In this config-... 

This micro mixer, named electrohydrodynamic (EHD) microfluidic mixer, comprises a simple T-channel structure (see Figure 1.5) [91]. After passing the T-junction, a bi-laminated stream is realized. Following a downstream zone for such flow establishment, a channel zone with several electrode wires on both sides of the channel is located. In this way, an electric field perpendicular to the fluid interface is generated. Thereafter, an electrode-free zone of the channel is situated for completion of the mixing initiated. 

M 1] [P 1] Microscopic observations of the flow were made to detect the changes induced by switching on an electric field for DC operation [91]. Initially a bi-laminated structure resulted owing to the T-junction contact. When the fluids passed the region of the adjacent electrodes, perturbations of the flow became clearly visible, i.e. the interfaces were deformed. The result was a color, i.e. species, distributed in a cross-sectional direction. 

M 21] [P 20] Mixing near a T-junction (channel 750 pm wide and 40 pm deep) is complete at a 0.17 pi min-1 flow rate when using a micro impeller at 120 rpm, as demonstrated by scanometric color index profiles providing line concentration profiles [32]. 

P 24] Computer simulations were carried out using the software Fluent 6 [68], A 3-D solid model of the T-channel micro mixer was built and named in Gambit The simulations were made solely for the zone of the T-junction, since for all other zones, including the downstream section of the mixing channel, laminar flow was assumed. Thus, a fine mesh of 173 000 brick elements could be used for the solid model. 

Simulation of liquid flow at the T-junction - liquid mixing... 

Based on these considerations, a schematic was proposed showing regions of vortices and of secondary cross flow in the T-junction by which the findings given above can be explained (see Figure 1.57) [68], This is said to resemble secondary flow of Prandtl s first kind as a result of centrifugal force when fluid flows in curved path. 

Figure 1.57 (a) Cross-sectional view of the image (b) at X-X showing the separation of a partially mixed zone and a recirculation zone, inducing cross flow for mixing, (b) Top view of the T-junction showing the respective distribution of the same zones [68] (by courtesy of Elsevier Ltd.). 

The T-shape was imprinted into a polymer substrate yielding a trapezoid cross-sectional shape [156], By excimer laser fabrication, a series of slanted wells beginning close to the T-junction were made. This microstructure was then sealed by a polymer cover. 

Mixer type Double T-junction micro mixer Sub-channel width, length 400 pm, -2 mm... 

These plates are inserted in a T-channel structure in a still thicker plate, directly at the T-junction at the ends of the two feed channels. In this way, a rectangular mixing chamber is formed in the outlet channel of the T-structure, having multinozzle arrays on both sides. The arrays can be positioned with and without offset to collide the jets directly and to let them flow aside. In the latter case, it is thought that eddies are produced at sufficiently high velocity of the jets. 

The carbon monoxide and chlorine gas feeds are mixed in the T-junction of the reactor and then guided through the catalyst bed of the reactor. The catalyst, carbon particles with a diameter of 53-73 pm, is preconditioned by heating the reactor at 150 °C for 2 h under a constant argon flow. A mixture of 2/3 CO and 1/3 chlorine (4.5 seem min-1) is fed into the reactor. The reactor was incrementally heated to 220 °C the pressure at the inlet was -132 kPa and nominally atmospheric at the outlet [39],... 

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