In the injection molding process the main source of heat inside the mold is coming from the molten plastic.
The coolant flowing through the cooling channels absorbs the heat, which leads to a rise in temperature inside of the coolant.
One indicator of the cooling efficiency is the coolant temperature in between the inlet and the outlet.
For technical parts the temperature difference should be less than 3 °C in order to ensure good part quality.
The coolant temperature help to evaluate the cooling design. It also help to estimate the number of bridges between cooling channels.
Higher flow rates, larger diameters and/or shorter cooling channels help to reduce the coolant temperature.