Barrel diameter

Traditionally, cyclone dimensions are multiples of outiet pipe diameter D. Typical barrel diameters are 2D but efficiency increases at constant up to a 3Z9 barrel diameter. Efficiency also improves as barrel and cone length are increased at constant up to the natural length of the vortex. At constant inlet velocity, efficiency increases as outiet diameter (and all ratioed dimensions in a family of cyclones) is decreased. Improved efficiency is attained at the... 

The inlet is usually rectangular and sometimes circular. In either case, projection of the flow path should never interfere with the outlet tube. If aveiy heavy sohds loading is anticipated, the barrel diameter should be increased shghtly. 

As plastics can have quite different viscosities, they will tend to behave differently during extrusion. Fig. 4.3 shows some typical outputs possible with different plastics in extruders with a variety of barrel diameters. This diagram is to provide a general idea of the ranking of materials - actual outputs may vary 25% from those shown, depending on temperatures, screw speeds, etc. 

Example 5.2 In a plunger-type injection moulding machine the torpedo has a length of 40 mm, a diameter of 23 mm and is supported by three spiders. If, during moulding of polythene at ITO C, the plunger moves forward at a speed of 13 mm/s, estimate the pressure drop along the torpedo and the shear force on the spiders. The barrel diameter is 25 mm. 

Three patents (MacLean, et al., 1982) assigned to Texaco filed in the latter half of 1980 resulted from an in-house review of all observed instances of erosion of cyclones in Texaco s FCC units. The patents specify that to minimize erosion and maximize collection efficiency, the length of the cyclone relative to its barrel diameter is to conform to the relationship ... 

With very small laboratory or pilot cyclones, some solids (large polymer beads, spherical particles, etc.) can sometimes bounce off the cyclone wall immediately across from the cyclone inlet and be deflected into the vortex. Very large particles can be found in the gas outlet stream of the cyclone with these very small cyclones and with particles that bounce. To increase cyclone efficiency with these types of solids, the cyclone barrel diameter can be increased. This increases the distance between the cyclone vortex and the wall and prevents most of the solids from bouncing back into the vortex. 

Table 5.3 Approximate Feed Channel Depths and Barrel Groove Dimensions as a Function of Barrel Diameters [49]...

Barrel Diameter, mm Feed Channel Depth, mm Grove Width, mm Maximum Number of Grooves... 

Grooved bore extruders are common on European extruders up to barrel diameters of about 120 mm and on some applications up to 150 mm diameter [44]. For a 60 mm diameter machine, the maximum feed channel depth for a PP resin application is about 5 mm and 6 mm for HDPE resin applications channel depths are not much larger than this for larger diameter machines. Ingen Housz and Meijer [44]... 

A version of this free helix device was also constructed that had a recycle system such that there was essentially no pressure change from the exit to the entrance of the extruder, as shown in Fig. 7.4. That device had a barrel diameter of 58 mm and it was used to measure the effect of the different parts of the screw on the extruder performance where pressure gradients could he imposed [5], The devices shown in Figs. 7.3 and 7.4 could be operated as a conventional extruder if hoth core and helix elements were driven at the same angular velocity with the barrel stationary. In another mode, only the helix was rotated in the same direction as the screw had been while the core and barrel were stationary. And finally the screw core was rotated in the same or different direction as the screw and the helix and barrel were stationary. 

Figure 7.4 Schematic of the modified free helix extruder with a barrel diameter of 58 mm and a flight clearance of 0.1 mm [5]...

Figure 7.19 Ratio of the pressure gradient calculated using the generalized Newtonian method to the pressure gradient calculated using the numerical method as a function of barrel diameter...

Figure 7.30 Experimental temperature increases for a Newtonian fluid (polypropylene glycol) as a function of the shearing time [47]. The data are for a square-pitched screw with a channel depth of 3.78 mm, a barrel diameter of 49.7 mm, and rotations at 55 rpm...

Spalding, M. A., Campbell, G. A., Carlson, F., and Nazrisdoust, K., The Effect of Barrel Diameter and Rotation on the Numerical Simulation of Single-Screw Extruders, SPE ANTEC Tech. Papers, 52, 792 (2006)... 

In order to meet the goals, the equipment manufacturers were forced to reduce the size of many of the components, including the motor size, gearbox, barrel diameter and length, and many auxiliary components of the line. It was hypothesized that the equipment manufacturers did not believe that the resin was as viscous as reported. The gearbox was, however, specified with a safety factor of 1.5 for the motor and belt sheave system installed. 

The melt-fed extruder is typically designed with a relatively short barrel length of 6 to 1L/D. Since the resin is molten when it enters the extruder, the motor size is relatively small compared to a plasticating extruder with the same barrel diameter. The extruders are typically starve-fed. That is, the extruder is operating at a screw speed that is higher than required, and thus the rate is not controlled by the screw speed, instead, the rate of the overall process is controlled by the feedstock addition rate to the compounding machine. 

Barrel Diameter mm Barrel Length, L/D Rate, kg/h Motor Size, kW Specific Rate, kg/(hrpm)... 

In polymer extrnsion, show that, for a single-flighted screw, the channel width is related to the inner barrel diameter by W = tvDs sinO. Clearly state any assnmptions yon make. 

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