The coolant temperature is determined by considering the recommended mold surface temperature for the plastic being molded and the feasibility of achieving this temperature.
Some thermoplastics need a higher surface temperature for better part finish. In such cases, heated water or oil may be used for cooling the mold. Generally the temperature of the coolant is lowered to achieve better heat transfer and reduced cycle time. However, try to keep the mold surface temperature close to the recommended value.
An inlet temperature 10 to 20°C lower than the desired mold temperature is suggested as a design guide. This will also be influenced by the coolant circulating plant available. There is no benefit specifying a coolant inlet temperature of 5°C if no chiller is available to achieve this value. The tower water temperature will vary according to its geographical location and ambient conditions.