How to Select the Right Air Cooled Chiller for Your Plastic Manufacturing Plant

Why Choosing the Right Air Cooled Chiller Matters for Plastic Manufacturing

Air cooled chillers are among the most widely used cooling solutions in plastic manufacturing facilities worldwide. Unlike water cooled systems, air cooled chillers reject heat into the surrounding air without requiring a separate cooling tower or condenser water system, making them simpler to install, easier to maintain, and ideal for facilities where water resources are limited.

Selecting the right air cooled chiller is not just about matching the unit's nominal cooling capacity to your machine nameplate. It requires a deeper understanding of your process heat load, desired coolant temperature, ambient conditions, and operational patterns.

Step 1: Calculate Your Actual Cooling Load

In plastic processing, the cooling load comes from part cooling, cylinder radiation (15-30% of total), hydraulic oil heat, and motor heat. A practical shortcut: estimate 0.8-1.2 kW per ton of cooling capacity for general-purpose injection molding. Precise formula: Cooling Load (kW) = Mass (kg/h) x Cp x (T_melt - T_eject) / 3600

Step 2: Determine the Required Leaving Water Temperature

Different plastic processes demand different temperatures: Standard injection molding (10-25C), Thin-wall high-speed molding (5-15C), Extrusion and blow molding (15-30C), Rubber molding (40-80C, requires MTC not chiller). The chiller's leaving water temperature must be lower than the process dew point.

Step 3: Evaluate Ambient Conditions

For every 1C rise above 35C design temperature, chiller capacity drops 1.5-2% and power consumption rises ~1%. Size the chiller with 10-15% safety margin for high summer temperatures. At elevations above 1,000m, apply a correction factor of 1.5% per 100m.

Step 4: Match Compressor Type to Your Application

Scroll compressors: Most common for plastic applications - excellent reliability, quiet operation, good part-load efficiency. Piston compressors: Suitable for smaller capacities with frequent on-off cycling. Screw compressors: Used above 50kW - can modulate capacity, ideal for plants with multiple machines.

Step 5: Check Flow Rate and Pressure Requirements

Ensure the chiller pump delivers sufficient flow (0.15-0.25 L/min per kW of cooling capacity) against total system pressure drop. Maintain a Delta-T of 3-6C between chiller supply and return water for stable temperatures.

Step 6: Consider Energy Efficiency Features

Variable speed fans (EC fans) reduce energy consumption by up to 30% in partial-load conditions. Capacity modulation via inverter-driven compressors eliminates wasteful on-off cycling. Modern microprocessor controls allow easy temperature setting and alarm management.

Step 7: Sizing Example

3 injection molding machines, each 20kW cooling load, 40C ambient, 15C leaving water required. Total load = 60kW. With 15% safety margin = 69kW. An 85-90kW air cooled chiller with scroll compressors provides comfortable headroom.

Conclusion

Choosing the right air cooled chiller requires calculating actual heat load, determining required coolant temperature, accounting for ambient conditions, selecting appropriate compressor type, verifying flow and pressure compatibility, and prioritizing energy-efficient features.