Melting with Drag Flow Melt Removal

2 Melting with Drag Flow Melt Removal 

The energy equation within the melt will include the conductive and the viscous dissipation terms as follows 

The boundary conditions for the momentum and energy balance equations are 

The velocity at any point uy(6) is determined by the rate of melting at the interface (Fig. 6.67), which is obtained from the Stefan condition or heat balance between conduction and the rate of melting at that interface, 

In order to reduce eqn. (6.282) we must And the temperature distribution for the solid. The energy balance for the solid is given by 

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A common flow problem in polymer processing is a shear flow with a temperature gradient as depicted in Fig. 6.58. For example, this type of flow occurs within the melt film that develops during melting with drag flow removal, as will be discussed later in this chapter. 

Figure 6.64 Schematic diagram of the melting process with drag flow melt removal.

Because of these limitations, and in particular because of the fact that, in such a mechanism, the temperature gradient at the wall that determines the heat flux to the solids drops exponentially with time, this melting mechanism is rather inefficient. However, the latter drawback can be alleviated if some mechanism continuously removes the molten layer. This, as shown in Fig. 5.3, can be accomplished either by applying a force normal to the heated surface, forcing out the melt by pressure flow, or by having the contact surface move parallel to its plane, dragging away the molten layer. These comprise the two... 

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