Selection of mold chiller: How to match cooling capacity and flow rate

Selection of mold chiller: How to match cooling capacity and flow rate
The cooling capacity of the chiller is calculated based on the total heat load of the mold water circuit, and the flow rate is calculated based on the number of circuits and the flow rate of a single circuit, with a margin of 15% -20% for both.
Calculate the heat load first
The heat load mainly comes from the heat release of aluminum liquid. Based on the weight of a single piece and the hourly module, a 14kg wheel hub with 6 modules per hour requires approximately 15-25kW of cooling capacity for heat release.
The heat dissipation of the mold to the environment will share a portion, and the actual selection can be based on 70% -85% of the calculated value.
This estimate is rough, but it is sufficient to determine the scale of the chiller. Accurate calculation requires mold thermal balance simulation.
Flow accumulates by circuit
The single loop flow rate is usually 8-20L/min. 8 sets of circuits are fully open, with a total flow rate of approximately 64-160L/min.
The rated flow rate of the chiller should be greater than the total flow rate, and it is recommended to leave a 20% margin. Insufficient flow will result in significantly higher water temperature in the end circuit.
The temperature difference between the inlet and outlet water should be controlled at 3-5 ℃. If the temperature difference exceeds 8 ℃, it indicates insufficient flow or insufficient heat exchange area.
The impact of temperature accuracy
The temperature control accuracy of ordinary chillers is ± 2 ℃, while high-precision models can reach ± 0.5 ℃.
The requirement for mold temperature for wheel hub molds is ± 5 ℃, which is sufficient for ordinary models. Precision structural components require ± 2 ℃, and high-precision models should be selected.
Insufficient temperature control accuracy, mold temperature fluctuations will be transmitted to the size. For parts with a wall thickness tolerance of ± 0.4mm, it is recommended to control the mold temperature fluctuation within ± 3 ℃.
Water quality and heat exchange
The heat exchangers of chillers are mostly plate or shell and tube type. When the water quality is hard, scaling in the heat exchanger will quickly reduce the cooling capacity.
Suggest using softened water or deionized water, with hardness controlled below 200mg/L. The recommended conductivity is below 500 μ S/cm.
Xinfeng Mold will indicate recommended water quality in the waterway interface description of the wheel hub mold to avoid customers using tap water for direct supply.
A chiller with several sets of molds
Matching the total heat load with the total flow rate is not recommended to simply estimate based on the number of mold sets.
One set of molds is in production, one set is in preheating, and one set is in standby mode, with the actual load only being the one in production.
The capacity of the chiller is often configured between multiple trolleys according to the formula of "number of molds produced simultaneously x single load x 1.2".
Common Misconceptions
Misconception one is to allocate chillers according to the number of mold sets. The standby mold does not generate heat load, and when matched according to the number of sets, it will be severely overloaded.
The second misconception is to ignore pipeline pressure loss. The pipeline is long and has many bends, and the actual flow rate may be lower than the rated value.
Misconception three is setting the water temperature too low. When the water temperature is below 15 ℃, the surface of the mold cavity is prone to condensation, which actually affects the quality.
Practical tips
The condenser of the chiller needs to be cleaned quarterly. The accumulation of dust on the heat sink will result in a 10% -15% decrease in cooling capacity and an increase in power consumption.
Installing a thermometer at the inlet and outlet of the chiller is closer to the actual working conditions of the mold than the display provided by the unit itself.
Frequently Asked Questions
Q: How is the cooling capacity of the chiller calculated?
Answer: According to the heat release estimation of aluminum liquid, take 70% -85% of the calculated value.
Q: How to match the traffic?
Answer: Accumulate by the number of circuits, leaving a 20% margin.
Question: What is the temperature control accuracy required?
Answer: ± 5 ℃ is sufficient for wheel hub components, while ± 2 ℃ is required for precision components.
Question: What is the appropriate water temperature setting?
Answer: Standing at 20-30 ℃, it is prone to condensation below 15 ℃.
Q: How many sets of molds does one machine come with?
Answer: According to the number of molds produced simultaneously, not the total number of sets.
Q: What are the requirements for water quality?
Answer: Hardness below 200mg/L, conductivity below 500 μ S/cm.
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