外文翻譯---轉(zhuǎn)筒干燥器的設計和高效化方面英文版

1、仲夥注蹲鈰概苑艋拜弧蜮桫嘎興設計巴巴工作室 www.88doc88.com 預呃沸佧盼赳摹往茳蔦漓凝氰謹仲夥注蹲鈰概苑艋拜弧蜮桫嘎興設計巴巴工作室 www.88doc88.com 預呃沸佧盼赳摹往茳蔦漓凝氰謹The three types of continuous dryers used throughout industry are, flash dryers, fluid bed dryers and rotary dryers

2、. With flash dryers the heat transfer from the gas to the suspended solids is high, and drying is rapid, with a drying time in the order of 3 to 4 seconds. Fluid bed dryers also have a short drying time though the re

3、sidence time is more variable and particle size dependent. A fluid bed dryer will have an average residence time of approximately 30 to 60 seconds. The third type of dryer, rotary dryers, has a low heat transfer rat

4、e in comparison. The residence time in a rotary unit varies from about 5 to 25 minutes depending on the product to be dried. Figure 1 is a typical velocity versus pressure drop curve associated with fluid bed units.

5、To achieve fluidization of a packed bed the air volume drag force must be equal to the net weight of solids in the bed. Figure 1 shows the increase in pressure with gas velocity and the point at which fluidization occ

6、urs. Fluid bed dryers take advantage of the solid gas contact and the fact that solid particles are discrete in the gas stream. The downside with fluid bed units is the high electrical energy required to maintain the

7、 pressure drop across the bed. Most dryers can operate with a gas temperature well above the boiling point of water but some products are limited for quality reasons, eg breadcrumbs. In this case dryers operating at

8、low gas temperatures, ie below the boiling point of the fluid to be evaporated, are mass transfer dominated. When the units are operated above the fluid's boiling point then heat transfer dominates the drying. Th

9、e effect of gas velocity, assuming negligible radiation and conduction, on the drying rate (constant drying rate, Nc) is proportional to the gas mass velocity, G, to the power of 0.8 (ie, G0.8). The effect of gas temp

10、erature is directly proportional to the energy transfer and drying rate (Nc), thus increasing the gas temperature will increase the drying rate. The effect of gas humidity on the drying rate is inversely proportional