Effective heat extraction can reduce the cycle time.
Effective heat extraction requires the consideration of the following variables.
The coolant flow rate should be high enough to ensure that the temperature at the outlet is within 2-3°C of the inlet temperature.
Effective heat extraction requires the fllow of coolant flow to be turbulent. Turbulence is indicated by the Reynolds number, which is calculated from the diameter of the cooling channels, the flow rate, and viscosity of the coolant. A Reynolds number of 10,000 is recommended.
The surface area of the cooling channel must be great enough to ensure that the temperature rise across the channel is 2-5°C.
Increasing the length or number of the channels improves the area available for heat transfer. This results in a higher pressure drop in the channel. If the diameter of the cooling channel is increased, a higher flow rate is required to achieve turbulence.
A balance has to be struck between the diameter and length of the cooling channels, and the pressure and volume characteristics of the cooling pump.
When these conditions have been optimized, the temperature rise across the metal is controlled by the placement of cooling circuits. Although, ideally, this should be no more than 5°C, it is more realistic to expect a temperature rise across the metal of 10-30°C.