Internal mixer heat transfer coefficient

A major problem in cooling rubber, in any process, is its inherently poor conductivity, which means that it is only cooled where it touches a cool surface. Thus, total heat removal depends on the area of the coohng surface and also on the way in which fresh rubber surfaces are moved into contact with that cooling surface. In internal mixers this depends mainly on the geometry of the rotors. Mixers with intermeshing rotors are less influenced by the friction or adhesion between the rubber and metal, and are, therefore, less sensitive to starting temperature. Rotor geometry also affects the overall heat transfer coefficient in a mixer. ... 

Heat Transfer Surfaces. When the process requires heat addition to or removal from the process fluid, the mixing tank must be equipped with appropriate heat transfer surfaces. Liquid motion supplied by the mixer enhances the heat transfer coefficient. Commonly used heat transfer surfaces, shown in Figure 6-8, include jackets, internal helical coils, and internal baffle coils. A jacket can be a tank outside the main tank, baffled, half-pipe, or dimpled. Each of these heat transfer surfaces can also be used in combination with a single coil or multiple heating coils installed within the space between the impeller and the tank wall. A suitable heat transfer fluid must be supplied on the service side of the heat transfer surfaces. 

Performance problems related to maldistribution also exist in cooling applications, especially where viscosity increases as temperature is lowered. At worst, case equipment could become inoperable, due to plugging of all but the center of the flow channel. This condition can be eliminated by the use of static mixer internals, discussed later. Heat transfer coefficients for laminar flow in empty pipe are correlated by... 

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