Chevron plate

Fig. 4.61. Stacking of MCPs to increase gain. From left single MCP, Chevron plate, and z-stack configuration. Note the loss of spacial resolution upon stacking.

Applications Most PHE applications are liquid-liquid seiwices but there are numerous steam heater and evaporator uses from their heritage in the food industry. Industrial users typically have chevron style channel plates while some food apphcations are washboard style. 

Design Standard channel-plate designs, unique to each manufacturer, are developed with limited modifications of each plates corrugation depths and included angles. Manufacturers combine their different style plates to custom-fit each seiwice. Due to the possible combinations, it is impossible to present a way to exactly size PHEs. However, it is possible to estimate areas for new units and to predict performance or existing units with different conditions (chevron-type channel plates are presented). 

Close examination of these areas under a low-power microscope revealed smoothly rippled, spherical surfaces in the weld region and a chevron pattern that pointed back to the weld in the plate. Cross sections cut through the weld revealed substantial subsurface porosity and regions where oxidized surfaces prevented metallurgical bonding of the weld (Fig. 

These weld defects not only substantially reduced the mechanical strength of the weld, the pores also formed stress-concentrating notches. Consequently, when the door frame was inadvertently struck during the scrap charging operation, a fracture initiated at the deficient weld and propagated rapidly through the %-in. (1.9-cm) plate, as revealed by the brittle appearance of the plate fracture and the directional chevron markings. 

Compared with traditional plate-and-frame exchangers, this design relies on a more loosely corrugated chevron pattern, which provides exceptional resistance to clogging. The plates are designed with few, if any, contact points between adjacent plates to trap fibers or solids. Some styles of this exchanger use wide-gap plates on the process side and conventional chevron patterns on the coolant... 

Figure 4-17A. Separation/Impingement action of Chevron-style mist eliminators. Flow Is up the V-shaped plates assembly. Courtesy of Bulletin KME - 12, Koch Engineering Co.

There are many baffle type impingement separators. The efficiency of operation for entrainment is entirely a function of the contacting action inside the particular unit. There are no general performance equations which will predict performance for this type of unit therefore manufacturers performance data and recommendations should be used. A few of the many available units are shown in Figures 4-28 to 4-31. Many use the Chevron-style verdcal plates as shown in Figures 4-17A and 4-30. 

One of the common impingement plate assemblies is of the Chevron zig-zag style of Figures 4-17A and 4-30. This style of impact separation device will tolerate higher gas velocides, high liquid loading, viscous liquids, reasonable solids, relatively low pressure drops. The collected... 

Theories of the oxidation of tantalum in the presence of suboxide have been developed by Stringer. By means of single-crystal studies he has been able to show that a rate anisotropy stems from the orientation of the suboxide which is precipitated in the form of thin plates. Their influence on the oxidation rate is least when they lie parallel to the metal interface, since the stresses set up by their oxidation to the pentoxide are most easily accommodated. By contrast, when the plates are at 45° to the surface, complex stresses are established which create characteristic chevron markings and cracks in the oxide. The cracks in this case follow lines of pores generated by oxidation of the plates. This behaviour is also found with niobium, but surprisingly, these pores are not formed when Ta-Nb alloys are oxidised, and the rate anisotropy disappears. However, the rate remains linear it seems that this is another case in which molecular oxygen travels by sub-microscopic routes. 

Impingement separators, 246, 257 Chevron style, 248, 255 Efficiencies, 246 Knitted wire mesh, 246 York-vane efficiencies, 248 Inertial centrifugal separators, 266, 268 Kinetic energy, pump system, 187 Lamella plate classifiers, 239 Line sizing work sheet, 107... 

In modem boilers, both FT steam spaces and WT steam drums incorporate various devices to promote the effective separation of steam from water and the production of dry steam. These devices include horizontal separators and baffle plates in the steam/water space, and chevron driers, cyclone separators, and secondary steam scrubbers in the steam space. Older or simpler boiler designs with steam release velocities of below 3 ft/s (0.9 m/s) may rely solely on the natural separation of steam from water. 

Steam dryers These provide closely spaced corrugated plates through which steam must pass. Chevron dryers and other dryer types reduce the velocity at which the steam passes, causing the impurities to drop out. 

Steam flow restrictions. Operating a boiler that has a restricted steam flow due to blockages or deposits in the chevrons, baffles, collecting pipes, splash plates, or pans (perhaps resulting from longterm adverse water chemistry conditions) may cause localized high steam velocities that lead to carryover. 

A. Westman, G. Brinkmalm, and D. F. Barofsky. MALDI Induced Saturation Effects in Chevron MicroChannel Plate Detectors. Int. J. Mass Spectrom. Ion Proc., 169/170(1997) 79-87. 

The simple shear test, also shown in Figure 16, was designed in the "chevron configuration to eliminate premature tensile failure at the corner between the leading edge and the central plate. The propellant at these corners will be compressed during most of the test. 

The Chevron channel plate ion detector assembly of an imaging atom-probe can also be replaced by a position sensitive particle detector combined with a data processor, as reported by Cerezo etal.5s (A position sensitive detector was used earlier for the purpose of field ion image recording and processing.59) With such a detector both the chemical identity and the spatial origin on the emitter surface can be found for each field evaporated ion. This position sensitive atom-probe can be used to study the spatial distribution of different ion species on the emitter surface as well as inside the bulk of the emitter with a spatial resolution nearly comparable to the FIM. For such a purpose, one carries out the field evaporation at an extremely slow rate so that no more than one ion is detected from the entire field ion emitter surface in each pulsed field evaporation. From the flight time of the ion its chemical species is identified, and from the location of the detector where the ion is detected the spatial origin of the ion is located. With a fast data processor, a two-dimensional distribution of chemical species on the tip surface can be... 

Fig. 3. 22 Magnetic sector atom-probe which uses a second order focusing 60° sector field. The line spectrum is displayed on a 7.5 cm diameter Chevron channel plate and a proximity focused screen, which can show the impact of single ions.

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