Tubes inserts

We are aware of three different kinds of tube insert, but all three are based on the idea of a metal spiral inside the tube. The commercial names are  

The Spirelf tube insert is a metallic coil stretched over the length of the tube and held in place at each end by straight wires. In ojjeration, when fluid flows through the tube, the Sparelf coil vibrates axially and radially. 

The concept is that this vibration reduces fouling and increases flow turbulence, producing an improvement in heat transfer coefficient However, there is also an associated increase in tube-side pressure drop of about 3 psi per pass at tube-side velocities of 3 ft/s. 

The main applications for Spirelf so far have been oil refinery preheat trains for CDU, VDU, FCC, and HDS units, and also high tube velocity applications as foimd in reboilers. 

The Turbotal tube insert cod, also referred to as a helicoid mobile, is designed to rotate within the tube. This is achieved by a mechanism at the tube inlet that holds the Turbotal insert in place but allows it to 

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Measurement of Fluid Flow hy Means of Orifice Plates, Nobles and Venturi Tubes Inserted in Circular Cross Section Conduits Punning Full, ISO 5167-1980(e), International Organization for Standardization, Geneva, Switzerland, 1980. 

Most of the AHoy 600 outer diameter tube corrosion has occurred in the region of the upper tubesheet near the open lane, ie, an untubed lane across the middle of the steam generator (16,17). The steam carries entrained droplets of water through the open lane to the upper tubesheet region where the droplets dry out and concentrate the chemicals. Long tube inserts have been used to sleeve tubes in this region where wall defects have been detected. 

ISO 5167-1 1991. Measurement of Fluid Flow by Means of Pressure Differential Devices-Fart 1 Orifice Plates, Nozzles and Venturi Tubes Inserted in Circular Cross-section Conduits Running Full. International Organisation for Standardisation, 1991. 

With a draft tube inserted in a tank, no sidewall baffles are required, and, the flow into the axial impeller mounted inside the tube is flooded to give a uniform and high flow pattern into the inlet to the impeller. The upflow in the annulus around the tube has sufficient velocity to keep particles in suspension, if necessary. 

The/3" —alumina tube inserted in a steel cell case which forms the negative terminal. The space between the ceramic tube and the cell case is the sodium compartment. 

Inspect the tube sheet for any signs of cracking (especially around the points of tube insertion) or leaking (perhaps from tube thinning caused by excessive, repeated, or poor tube-end rolling). 

Adventitious surfactants also have a marked effect on the mechanism of coalescence. In studying the coalescence of curved water surfaces, Lindblad (L8) used aged distilled water that was stored for about 30 h in a polyethylene bottle opened to the air through a narrow polyethylene tube inserted in the water. He found that if fresh distilled water (water exposed not longer than 1 h to the air) was used, the delay time in coalescence was approximately half as long. Consequently, he concluded that this difference is due to some form of contamination which settled into the water or onto the water surface. 

Thiophenes of type 31 (X-Y = CH) were generated via Lawesson s reagent-mediated cyclization of 1,4-dicarbonyl compounds 30 under microwave irradiation in the absence of solvent [37]. The reaction was carried by mixing the two solid reagents in a glass tube inserted inside a household microwave apparatus and irradiating until the evolution of H2S ceased. An interesting application of this method is the preparation of liquid crystals and other ferro- and antiferroelectric material such as compound 33 (Scheme 10). 

Two sets of stoppers are very useful, one set unbored and a second set with a single hole bored in them to carry blowing-tube connectors. A longer piece of glass tubing inserted into the hole will also form a very adequate handle when working small pieces of apparatus. 

It might be expected that EN via tubes would have been used widely before the development of parenteral nutrition (PN) however, this was not actually the case. EN via tubes inserted down the mouth or nose into the stomach and also via rectal tubes was used occasionally in the decades before the development of PN in the 1960s.1 However, modern techniques for enteral access, both the placement of the tubes themselves and the materials for making pliable, comfortable tubes, had not yet been developed. Before the PN era, the formulas delivered by the tube route often were blenderized foods. The National Aeronautics and Space Administration effort in the United States in the 1960s led to the development of low-residue (monomeric) diets for astronauts. These diets were adapted for use in sick patients requiring EN. Nonvolitional feedings in patients who cannot meet nutritional requirements by oral intake thus include EN and PN these techniques are collectively known as specialized nutrition support (SNS). 

Tympanostomy tube A small plastic or metal tube inserted in the eardrum to keep the middle ear aerated and improve hearing in patients with chronic middle ear effusion. 

Tubular reactors can be used for multiphase reactions, as discussed in the previous section. However, it is often difficult to achieve good mixing between phases, unless static mixer tube inserts are used. 

In addition to the use of antifouling chemical agents to mitigate the effect of fouling on the tube-side, twisted tubes can be used rather than plain tubes. These have surface irregularities. Plain tubes can also be fitted on the inside with tube inserts. Twisted tubes and tube inserts promote additional turbulence and pressure drop and reduce the surface temperature of the tube to mitigate fouling. Tube inserts will be dealt with in more detail later. 

The enhancement ratio (fiie/hi) for tube inserts can be correlated as a function of Reynolds number based on the internal diameter of the tube Re = pVdi/fi10. Different tube inserts can be compared on the basis of plots of enhancement ratio (hTe/hT) versus Reynolds number. 

Table 15.6 Thermal performance of tube insert devices.

Table 15.8 shows the enhancement ratios for various tube inserts. 

Table 15.8 Enhancement ratios for heat transfer of various tube inserts.

Thus, all of the tube inserts will potentially provide the required enhancement without the need for extra heat transfer area. However, it would be preferred to have the enhancement with minimum increase in pressure drop. Table 15.9 shows the increase in friction factor for the various inserts. 

Table 15.9 Enhancement ratios for friction factor of various tube inserts.

Also, as discussed in Chapter 15, rather than install additional heat transfer area to cater for the new operational requirements, heat transfer enhancement can be considered. Changes to the number of tube passes or the baffle arrangement might allow the heat transfer coefficient to be enhanced. Alternatively, tube inserts could be used. This was discussed in Chapter 15. The major disadvantage in using heat transfer enhancement is that it increases the pressure drop. In retrofit this can be important, as the pumps driving the flow might be limited in their capacity to meet the required increase in pressure drop. 

Hi) Chromatogram obtained with a 12.5 cm x 4.6 mm tube inserted as above. 

A tank that is vented to the atmosphere contains a liquid with a density of 0.9 g/cm3. A dip tube inserted into the top of the tank extends to a point 1 ft from the bottom of the tank. Air is bubbled slowly through the dip tube, and the air pressure in the tube is measured with a mercury (SG =13.6) manometer. One leg of the manometer is connected to the air line feeding the dip tube, and the other leg is open to the atmosphere. If the manometer reading is 5 in., what is the depth of the liquid in the tank ... 

Figure 6. The relationship between mean circulation time and variance of the circulation time distribution for a 150-mm diameter fluidized bed with draft tube insert (from Cheng, 1993).

Our library synthesis was carried out with a set of 27 tube-shaped solid phase synthesis support, called MicroTubes. These supports are prepared by radiation grafting of polystyrene ( — 350 pmol) onto polypropylene tubes, chemically functionalizing the polystyrene with aminomethyl groups to afford about 55 imol of amine per tube, inserting a reusable Rf ID tag into each tube, and heat-sealing the tube ends to prevent loss of the tag. The chemical conversion of all 36 aminomethyl tubes was carried out simultaneously using standard procedures with rink amide linker, each with —46 pmol of available amine per tube.1 2... 

A small sample volume in a flowing solution can be obtained by introducing the sample from a capillary tube inserted into a flow cell (Ambrose et al., 1999) (Figure 11.14). This tube is surrounded by a rapidly flowing sheath fluid so that the sample stream is focused as it exits the capillary. The sample stream resulting from such... 

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