Mechanical energy screw

Is any heat generated during the mixing or physical processing of substances YES Some temperature increase due to mechanical energy of screw conveyor... 

Up to 80 % of the overall mechanical energy input in the twin screw extruder takes place in the plastification zone. Unfortunately, currently only rudimentary modeling capacities for the melting process are available. 

The specific energy input is the most important characteristic value. It is characteristic to each product and applies irrespectively of the size of the extruder. Generally, only measurable value is the specific mechanical energy input Pslx,tif lnCci, via the screw shafts. This is calculated using the following equation ... 

Figures 4.20 to 4.22 show the relationship between screw speed, throughput, specific mechanical energy input, and melt temperature. It is apparent that melt temperature and specific mechanical input increase as screw speed increases and decrease as the throughput increases (see Fig. 4.20 and Fig. 4.21), while the temperature increase in relation to the screw speed is greater than the temperature decrease in relation to the throughput. Therefore, according to the above equation, the melt temperature ultimately rises as the specific energy input rises (see Fig. 4.22).

Figure 4.20 Influence of screw speed on melt temperature, throughput, and the specific mechanical energy input...

The polymer or the polymer solution cools down because the vaporization energy required for the vaporization process is taken from the in-fed polymer solution. The required ZSK size depends on the gas quantity to be removed, the gas velocity, the rheological behavior of the polymer melt, and the thermodynamic behavior of the degassed components, the screw speed, and the throughput. Mechanical energy has to be introduced in the processing zone... 

Solid polymer in the form of pellet or powder dropped into the screw channel from the hopper is compacted into a solid plug due to the screw rotation and the solid plug is forced to rub on the heated barrel surface. The solid plug is plasticated or melted in screw extruders primarily by the mechanical energy provided by the drive motor rather than the thermal energy from the heated barrel. 

Extrusion (dry heat) cookers have been ideal for stabihzation because excess moisture is not added, eliminating the need for drying. The heating of the bran occurs through conversion of mechanical energy of the screw drive to heat the bran. Temperatures used for stabilization vary from 100° to 140°C. The bran is kept hot for 3-5 minutes after extrusion to ensure lipase inactivation. The hot bran is then cooled using ambient air. 

Plastification of polymeric material requires energy to be transferred from an outside source into the material. In the twin-screw extruder, this energy transfer occurs through both mechanical and thermal mechanisms. However, as the extruder gets larger, the surface to volume ratio decreases significantly. Therefore, mechanical energy transfer is the dominant mechanism for plastification. 

The drive system supplies the mechanical energy to the polymeric material by rotating the screw. This system consists of a motor, a speed reducer, and a thrust bearing. 

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