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Why should the use of desiccant dryer
Date:2017-01-11 15:18:58 Hits:2649
Plastic (plastic) in front of the granulation process is different, so the gas moisture content and moisture absorption is different, so in the molding, easy to have a bubble, silver, poor transparency, according to the crack resistance for true strength is not enough, flow mark size stability factor. Now most of the engineering plastics is hygroscopic, when the plastic packing bag from moisture seal out the exposure in the atmosphere, began to absorb moisture from the atmosphere, if the traditional hot air drying machine barrel, because with moisture to air dry plastic, so it is unable to prevent moisture absorption to plastic.
In the process of dehumidification, the movement of the material particles in the air flow is divided into the acceleration phase and the constant velocity stage. In the acceleration stage, the drag force and the buoyancy of the particles is larger than the gravity and, with upward acceleration, the relative velocity of particles with gas is a variable; with particle velocity increases, the drag force decreases gradually, until the 3 force vector and zero particle in uniform motion stage, the relative air velocity and particles is a constant.
The relative motion of particles with gas have great effect on the rate of heat transfer between the particles and the air, in the initial stage of drying, particles just entering the drying tube rises when the speed is zero, and meet with high speed hot air flow to get up the speed, when the convection heat transfer coefficient of the two phase, accelerating the rise of material particles enter the accelerated motion, drying stage, solid particles obtained in accelerated phase heat accounted for more than half of the whole drying stage to obtain heat. In the later stage of drying, the convective heat transfer coefficient is greatly reduced and the drying efficiency is reduced when the rising velocity of solid material is close to that of air. In the drying process of changing the relative velocity of gas-solid two-phase flow, turbulence intensity increased around the particle boundary layer, as far as possible to enlarge the contact area of gas-solid two-phase, increase the contact time, are effective measures to improve the drying efficiency.
In the process of dehumidification, the movement of the material particles in the air flow is divided into the acceleration phase and the constant velocity stage. In the acceleration stage, the drag force and the buoyancy of the particles is larger than the gravity and, with upward acceleration, the relative velocity of particles with gas is a variable; with particle velocity increases, the drag force decreases gradually, until the 3 force vector and zero particle in uniform motion stage, the relative air velocity and particles is a constant.
The relative motion of particles with gas have great effect on the rate of heat transfer between the particles and the air, in the initial stage of drying, particles just entering the drying tube rises when the speed is zero, and meet with high speed hot air flow to get up the speed, when the convection heat transfer coefficient of the two phase, accelerating the rise of material particles enter the accelerated motion, drying stage, solid particles obtained in accelerated phase heat accounted for more than half of the whole drying stage to obtain heat. In the later stage of drying, the convective heat transfer coefficient is greatly reduced and the drying efficiency is reduced when the rising velocity of solid material is close to that of air. In the drying process of changing the relative velocity of gas-solid two-phase flow, turbulence intensity increased around the particle boundary layer, as far as possible to enlarge the contact area of gas-solid two-phase, increase the contact time, are effective measures to improve the drying efficiency.
