Meaning
Dimensionless ratio in heat transfer and rheology compares the rate of heat generation from viscous dissipation to the rate of heat removal by temperature-dependent viscosity changes. A high nahme number indicates that the fluid viscosity will drop rapidly due to internal heating, which further alters the flow profile. This value is a primary indicator of whether a process will reach a stable thermal equilibrium or experience a runaway temperature increase.
Temperature Sensitivity
Materials with a high activation energy for flow are more prone to the effects measured by this ratio. When the nahme number is large, even a small amount of mechanical work can cause a drastic reduction in the flow resistance of the polymer.
Shear Localisation
Non-uniform heating across a die or channel creates layers of fluid with different velocities. If the nahme number exceeds a critical threshold, the flow becomes concentrated in a hot, low-viscosity zone near the walls. This effect leads to poor mixing and can cause the outer layers of a product to have different properties than the core.
Energy Balance
Designers use this calculation to size the cooling channels in high-speed extrusion equipment. Managing the nahme number prevents the material from overheating to the point of chemical degradation. A process that ignores this balance will suffer from inconsistent dimensions and poor surface finish.
