Frictional heat generation

If one would want to determine optimum temperature settings from data on the coefficient of friction at various temperatures, there is an additional complication that should be taken Into account. This complication is the frictional heat generation that occurs in the solids conveying zone. As a result of this frictional heat generation, the temperature at the interface between solid bed and barrel may be substantially higher than the barrel temperature setting indicates. 

On the screw surface, the relative velocity between the solid bed and screw is simply the solid bed velocity. Thus, the frictional heat generation on the screw is  

On the barrel surface, the relative velocity between solid bed and barrel can be written as  

The frictional heat generation on the barrel surface is sincp 

This tends to slow down the temperature development at the interface and extends the length of the solids conveying zone. When the temperature at the interface reaches the melting point, the solids conveying zone will terminate because polymer melt will form at the interface and the solid-to-solid frictional mechanism will cease to operate. 

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The method of application, whether splash, spray, jet or mist, will have an effect on the lubricant. If oil is atomized, its surface area is increased and it is much more easily oxidized. The frictional heat generated by the meshing teeth will increase the rate of oxidation. The dissipation of... 

Proper chain-drive lubrication increases drive life by dissipating frictional heat generated in the joint area. Heat varies according to the chain speed, horsepower transmitted, center distance, sprocket ratio, drive size, amount of lubricant, and viscosity. It generally ranges from surrounding temperature to 60 to 70°F above the ambient temperature. Normal chain drive temperatures should not exceed 180°F. 

When oil-based binders are used, the frictional heat generated during buffing can cause the binders to bum. This in turn leads to the requirement for additional cleaning with alkaline soaks. When properly used, greaseless compounds produce parts that leave the wheel clean and dry. Greaseless compositions also tend to adhere to the surface of the wheel so that wheel life is extended. 

Erosive wear can be considered to be an interfacial wear where the energy evolved in the wear is dissipated. The third component in the wear process removes some of the frictional heat generated when the wear particle strikes the surface of the sample. 

Parison cooling is an integral part of the process that has been treated by a number of researchers (103-105). The principles are based on contact solidification without deformation, as discussed in Chapter 5. A special complication is the frictional heat generation in injection blow molding between the rod and the parison. 

By the time the material reaches the die plate, it is under high pressure, 1379-4137 kPa (200-600 psi) and has been cooked to some desirable degree based on moisture level and temperat4ure. Oilseeds usually receive a mild cook that converts them into a tacky, elastic-like condition. The injected steam condenses from the vapor state as it is absorbed into the material and releases its heat of vaporization. This sudden release of energy helps to heat the oilseed. Frictional heat generated by the rotating shaft continues the heating. 

F) because of the excessive frictional heat generated at high screw speed (90 RPM)... 

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