Design And Development On The Rotating-heat-pipe Cooling Roller Of The Mill

Roller mill is one of the main crushing equipments in flour factory, and its main workingcomponents are two rollers, whose surface should be kept certain hardness and wearresistance. When the raw materials roll into the roller mill, they are shattered by extruding,cutting and grinding. In order to produce high quality flour, the wear resistance, themachining properties, the material, the structure and manufacture method of the roller havebeen widely studied. But the following question generally exists in the process of production:with the roller continuous extruding, cutting and grinding the material, its surface temperaturewill gradually increase, even then the temperature could rise too high, which not onlydamages the nutrition of the flour, including the starch, protein and vitamin and so on, andeasily causes the evaporation and condensation of the water in material, result in the powderform forming in the cabinet surface, the tubes and transportation equipments of the roller mill,and the reduction of the sieving efficiency and the production of the roller mill.In connection with above problems, in this paper, based on the research of the cooledgrinding roller,the heat transfer principle of rotating heat-pipe was innovated utilized in theheat dissipation of the roller, and a rotating-heat-pipe cooled roller was designed anddeveloped in the paper. The roller itself grinded materials as a grinding roller, and was used asa rotating heat pipe to dissipate the heat on the whole. Through experiment performance ofrotating heat-pipe, the result indicated that it could effectively transfer the heat, and also couldbetter reduce the surface temperature of grinding roller and the temperature of the droppedmaterials. The specific research works of this paper are as follows:1. By analyzing the heat transfer process of the cooled grinding roller, this papercalculated the various main thermal resistance of the heat transfer process. For minimizing themost main thermal resistance, the structure of the rotating-heat-pipe cooled grinding rollerwas designed in the paper. By calculating, that was to determine the work liquid material, thefluid-filled ratio, the inner diameter of the roll, the fin height, spacing, and thickness of therotating-heat-pipe cooled roller.2. Confirming the vacuating method of the rotating-heat-pipe cooled grinding roller. Thevacuum was the necessary condition for the work liquid to transfer heat, so vacuum was one of the most important procedures in manufacturing the grinding roller. Through analyzing thecharacteristics vacuum system and heat-exhausting vacuum system, the later was adopted tovacuate.3. The filling quantity has great influence on the heat transferring performance of therotating-heat-pipe cooled grinding roller. VOF model of the Fluent was used to research theliquid film distribution under the540rpm,80W ‘s heating power and15%～30%fill ratio.The research found that, at the2mm end of the roller that was also the evaporation section,liquid membrane wetting rate increased with the increasing of fill ratio. When fill ratio lessthan twenty five percent, the inner wall of the evaporation section was partially wet. When fillratio more than twenty five percent, the wall was wet wholly. The best filling liquid quantitywas twenty five percent, which could basic consistent with the theory calculation.4. Having created the rotating-heat-pipe cooled grinding roller and tested the heattransfer performance, the results showed that it could be started in17min and the condensertemperature continued to rise with time prolonged, which indicated that it could efficientlytransfer heat. The surface temperature basically maintained invariable along the tube, and themaximum temperature difference was5.9℃,which showed that it was in good workingcondition and there was no non-condensable gas.5. The study of working effect of the rotating-heat-pipe cooled grinding roller in the mill.The results showed that the average temperature of the roller surface was5~7℃lower andthe average temperature of the drop materials was7.0~12.1℃lower than the common roller.