Only limited information is available about the power requirements of shredders.
Various estimates indicate that the hammermill is grossly inefficient, with only
about 0.1% to 2.0% of the energy supplied to the machine appearing as increased
surface energy of the product solids.26 Part of the explanation for such low efficiencies
lies in the plastic deformation and viscoelastic flow that accompanies shredding;
these deformation processes require many times more energy than the creation of
new surface area.
The efficiency of a shredding operation depends on how the energy is applied
and on how the material reacts to it. For example, a roll mill, which crushes materials
but does very little shearing, would waste energy trying to shred a newspaper.
Also, since fracture in brittle materials occurs progressively with flaws building up
within the particle until the particle breaks up, the rate of application of the force is
important. Because there is a time lag between the application of the force and eventual
fracture, a machine that applies load rapidly is inherently inefficient, since more
energy is required than if the force could be applied more slowly. It follows that for
some high-speed machines, a slower speed could result in less energy use, at least to
the point at which the rotor inertia is too low and the energy requirement once again
increases with decreasing speed. Higher speeds, nevertheless, produce the finest
product particle size, but this requires more energy.
Only limited information is available about the power requirements of shredders.Various estimates indicate that the hammermill is grossly inefficient, with onlyabout 0.1% to 2.0% of the energy supplied to the machine appearing as increasedsurface energy of the product solids.26 Part of the explanation for such low efficiencieslies in the plastic deformation and viscoelastic flow that accompanies shredding;these deformation processes require many times more energy than the creation ofnew surface area.The efficiency of a shredding operation depends on how the energy is appliedand on how the material reacts to it. For example, a roll mill, which crushes materialsbut does very little shearing, would waste energy trying to shred a newspaper.Also, since fracture in brittle materials occurs progressively with flaws building upwithin the particle until the particle breaks up, the rate of application of the force isimportant. Because there is a time lag between the application of the force and eventualfracture, a machine that applies load rapidly is inherently inefficient, since moreenergy is required than if the force could be applied more slowly. It follows that forsome high-speed machines, a slower speed could result in less energy use, at least tothe point at which the rotor inertia is too low and the energy requirement once againincreases with decreasing speed. Higher speeds, nevertheless, produce the finestขนาดอนุภาคของผลิตภัณฑ์ แต่นี้ต้องใช้พลังงานมากขึ้น
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