Meaning
Thermal energy transfer rates between a fluid medium and a solid boundary describe the intensity of heat removal during the cooling stage. Convective wall heat flux determines how quickly the mould steel absorbs energy from the hot polymer melt. The rate depends on the temperature difference between the surface and the internal cooling channels.
Coolant Efficiency
Fluid velocity within the cooling lines dictates the turbulence required for effective heat exchange. Convective wall heat flux increases when the flow enters the turbulent regime (Reynolds number above 4000). High flow rates maintain a low temperature rise across the cooling circuit.
Flow Velocity
Constant pumping pressure ensures that the heat removal rate stays within the required specification. Convective wall heat flux drops if scaling or rust builds up inside the channels. Regular maintenance of the water system prevents this drift in cooling performance.
Fouling acts as an insulator that reduces the effectiveness of the coolant. Monitoring the pressure drop across the mould helps to identify when the lines need cleaning. Operators can also track the temperature difference between the inlet and the outlet.
Thermal Gradient
Temperature differences across the cavity wall create the driving force for energy movement. Convective wall heat flux is a local value that can vary across the tool surface.
