Mechanical energy, specific

The power consumption of an extruder was measured with a standard wattmeter connected to the extruder drive unit. These results were converted into an index of specific mechanical energy (SME) consumption according to an equation formulated by Levin [2, 3]  

The investigations firmly established that changes in SME during TPS production are affected by material blend moisture content the higher the material moisture, the higher the SME values. The highest SME values recorded (0.076 kWh kg ) related to potato starch of 20% moisture and 20% glycerol content. 

Potato Starch Potato starch Potato starch Cornstarch Wheat starch (Lomza) (Braniewo) (AVEBE) 

Evident influences of the screw rotation speed, the mixture composition, and the moisture content of the raw materials on the temperature profile along the barrel of the extruder were recorded. Changes in the TPS temperature at the slit die depended predominantly on the screw rotation speed used. 

It has been reported that application of a temperature range running from 80-100 °C and an extruder screw rotation range of 80-100 rpm for thermal treat- 

---

Figure 1 Influence of the specific mechanical energy on the water-solubility (corrected from the blank values) of some raw materials...

Investigating coextrusion of com meal and WPI, Onwulata et al. (2003b) found that the melt temperature of the extmdate was more of an indicator of physical properties than specific mechanical energy. Quality attributes such as breaking strength, color, and expansion index were related to melt temperature measured at the die. 

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 ... 

Figure 4.19 Specific mechanical energy input for different volume- and torque-limited processes (according to Coperion Werner Pfleiderer)...

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...

One of the first applications of biodegradable materials is based on the cooked, extruded, and expanded starch known from the food and chemical sectors (Fig. 14.23). Starch is cooked with water in the extruder and chemically modified as necessary or mixed with plasticizers, then expanded to a starch foam and dried. The extrudate is ground so that the functional properties thus created can be used in the food/chemicals sector. The foamed, cut, and dried extrudate is the end product for loose-fill packaging applications. The degree of expansion is a measure of the foam texture. It increases strongly with product temperature at the die, helped by a higher specific mechanical energy input. However, both measures increase the water-solubility of the product. 

Kim and White (2004) Polymerization of poly- s-caprolactone Engineering model linking residence-time-model, shear-effects model and reaction conversion during extrusion Reaction conversion and from extruder via correlating specific mechanical energy and Mw... 

The number of torque limited processes is about 70 % [WH04b], The reason for this is explained in Fig. 10 where a standardized maximum output (volume specific output relative to speed and cube of axial distance) is plotted as a function of the diameter ratio. The descending curves indicate the torque limited output rate for different extruder series and specific mechanical energy inputs. The ascending curves indicate feed limitations for non-fluidized powder or granules with densities between 0.1 and 1.0g/cm ... 

Mercury-intrusion plots of calcined alumina extrudates from the top to the bottom, the specific mechanical energy input during mixing of the pastes was increased L/S is the ratio liquid to solid in the extrusion paste. 

To demonstrate the viability of these multi-scale solutions, the multi-scale reactor is first considered as a bundle of parallel tubes or channels, corresponding to the subflows, with a channel diameter D, a length L and a total number of channels N. The heat-transfer characteristic time, the reactor volume and the specific mechanical energy can be expressed as a function of these independent geometric parameters. Moreover, the ratio of the specific energy of a reactor after intensification (subscript 2) and before intensification (subscript 1) can be related to the features of interest as follows ... 

The ratio of specific mechanical energy describes the gain in sustainability. A value lower than unity indicates that the multi-scale design (subscript 2) requires less energy. 

The specific mechanical energy consumption (SMEC) is obtained by dividing the power consumption by the mass flow rate (throughput) ... 

When the throughput is expressed in kg/hr, the units of SMEC become kW-hr/kg. In scale-up it is often desirable to keep the specific mechanical energy consumption constant. 

ViUmow T, Kretzschmar B and Potschke P (2010) Influence of screw configuration, residence time, and specific mechanical energy in twin-screw extrusion of polycaprolactone/multi-walled carbon nanotube composites. Compos Sci Technol 70 2045-2055. 

Specific mechanical energy (SME = screw energy input/kg of product) Extruder average percentage fin, mixing mass, and mixing rotations Mixedness (e.g., NMR, AFM, or ACp via DSC if more than one phase)... 

---