Channel depth ratio

Screw Section Flight Radii to Channel Depth Ratio... 

D. The channel depth ratio varies from less than 2 to 4. The compression ratio, CR, has been defined as a ratio of the screw flight volume... 

Channel-depth ratio n. In an extruder screw, the ratio of the depth in the first turn of the screw at the feed end to the depth in the last turn at the dehvery end. If the lead of the screw is constant, the channel-depth ratio is shghtly larger than the chaimel-volume ratio (which follows). 

Compression ratio n. In an extruder, the ratio of the volume of the first turn of the feed section to that of the last turn of the metering section. This ratio is a rough indication of the total compaction performed on the feedstock. More precisely called the channel-volume ratio or, for a screw of constant pitch, channel-depth ratio. 

Channel depth in feed section 0.15-0.20 D Channel depth ratio 2-4... 

Figure 5 Scale-Up Implications Change of Pellet Size to Channel Depth Ratio with Machine Size...

Pfund et al. (2000) studied the friction factor and Poiseuille number for 128-521 pm rectangular channels with smooth bottom plate. Water moved in the channels at Re = 60—3,450. In all cases corresponding to Re < 2,000 the friction factor was inversely proportional to the Reynolds number. A deviation of Poiseuille number from the value corresponding to theoretical prediction was observed. The deviation increased with a decrease in the channel depth. The ratio of experimental to theoretical Poiseuille number was 1.08 0.06 and 1.12 zb 0.12 for micro-channels with depths 531 and 263 pm, respectively. 

Equations (3.11) and (3.12) show that the friction factor of a rectangular micro-channel is determined by two dimensionless groups (1) the Reynolds number that is defined by channel depth, and (2) the channel aspect ratio. It is essential that the introduction of a hydraulic diameter as the characteristic length scale does not allow for the reduction of the number of dimensionless groups to one. We obtain... 

In the simplest and most often used form, the screw has a free channel cross-section that diminishes at a steady rate from the feed to the delivery end. The ratio of the channel depths from feed to die region along the screw is usually referred to as the compression ratio, since it gives a crude indication of the relative conveying capacities at feed and discharge. 

Due to the complicated helical screw geometry and the assumption that the down-channel drag flow was a result of matching the screw core velocity to the modeled barrel velocity, the literature assumption that the flow occurs in a rectangular channel is reasonable only if the ratio of channel depth to width is small, that is, a channel with a small aspect ratio (H/W). A schematic of the channel depth to... 

The injection-molding press was producing a part and runner system that had a mass of 2.15 kg. The mass was plasticated using a 120 mm diameter, 8L/D screw. The screw used for the process had a barrier melting section that extended to the end of the screw, as shown by the specifications in Table 11.9. That is, the screw did not have a metering channel. Instead, the last sections of the barrier section were required to produce the pressure that was needed to flow the resin through the nonreturn valve and into the front of the screw. The specific rotational flow rate for the screw for the IRPS resin was calculated at 9.3 kg/(h-rpm) based on the depth of the channel at the end of the transition section. The screw was built with an extremely low compression ratio and compression rate of 1.5 and 0.0013, respectively. For IRPS resins and other PS resins, screws with low compression ratios and compression rates tend to operate partially filled. The compression ratio and compression rate for the screw are preferred to be around 3.0 and 0.0035, respectively. The flight radii on the screw were extremely small at about 0.2 times the channel depth. For IRPS resin, the ratio of the radii to the channel depth should be about 1. 

The lead length was 133 mm for the main flight of the screw. The main flight width and clearance were 12 and 0.12 mm, respectively. The compression ratio was 2.7 and the compression rate was 0.0090. The ratio of the flight radii to the local channel depth was 1.0 in all sections. The specific rotational rate was calculated at 8.5 kg/(h-rpm). 

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