Induction heating dumps a lot of energy into metal fast—often in just a few seconds. That energy also migrates into your copper coil, power leads, and surrounding hardware.
If you don’t pull heat out quickly and consistently, coil temperature drifts, coupling efficiency drops, seals fail, and parts drift out of spec. A well‑chosen chiller fixes those problems.
Below, you’ll find expanded, hands‑on guidance for engineering teams tasked with keeping induction systems stable shift after shift.
Why Coil Temperature Matters
When copper runs hotter than planned, its electrical resistance climbs roughly 0.4 % per °C. Your generator senses the change and pushes extra current to maintain field strength. That shift alters penetration depth and can push part temperature beyond your set window. In aerospace work, a 3 °C over‑shoot can seed sub‑spec γ′ in turbine blades; NADCAP auditors will see it in micrographs and reject the batch. On an automotive line, you risk shallow case depths on gears, leading to premature wear in the field.
Takeaways for engineers
- Add an inlet Pt100 probe within 200 mm of the coil. Log the reading; if coolant creeps above 30 °C, you’ll catch it long before the coil softens.
- Tie the probe to a generator interlock. Stop RF output if return water exceeds 40 °C or if flow collapses.
- Model coil impedance vs. temperature at design stage. That data helps you set realistic chiller alarms and prevents nuisance trips.
Estimate the Heat Load
Start with measured delivered power, not the generator’s nameplate. Use a power analyzer between the transformer and coil. Multiply average delivered kilowatts by 0.3 to estimate heat dumped into the coolant. For a 60 kW delivered load, that’s about 18–20 kW of waste heat. Add 10 % for hot summer days and 10 % for scale buildup, then pick the next‑size chiller.
Takeaways
- Use portable ultrasonic flow meters during a test run to confirm return‑water ΔT—then back‑calculate real heat load.
- Oversize by 20 % at most; an oversized chiller short‑cycles, which kills compressors.
- If heat load varies widely, choose a chiller with variable‑speed fans or compressors. That option costs more up front but slashes energy use.
Flow and Temperature Targets
Supply water in the 22–25 °C range and allow no more than a 5–7 °C rise. This band keeps copper below 55 °C—well away from its annealing threshold—and leaves margin for summer ambients. High‑frequency gear hardening benefits from turbulent flow; aim for Reynolds numbers above 20,000. With 3/8‑inch copper tube, that’s roughly 20 liters per minute.
Practical tips
- Split large coils into two parallel circuits if one hose can’t reach required flow.
- Install a bypass valve with an orifice plate so the pump never dead‑heads when the generator sits idle. You protect seals and bearings.
- Add a dew‑point sensor in humid climates. If inlet water is below dew point, wrap the coil in closed‑cell insulation or raise setpoint to prevent moisture bridges and arcing.
Open vs. Closed Loops
Open cooling towers cost less up front, but they expose copper to oxygen, calcium, and biofilm. Corrosion can thin 1 mm copper in a year. Closed loops use treated water or 30 % glycol, holding dissolved oxygen under 0.5 ppm and pH in the 8.5–9.2 range.
What to consider
- Closed loops allow sub‑ambient setpoints—handy if your generator derates above 35 °C.
- Open loops need regular chemical dosing. Budget for biocide and anti‑scale treatments.
- Hybrid systems exist: closed induction loop on a plate heat exchanger tied to an outdoor dry cooler. You get low‑maintenance water around your coil and lower capital than a full glycol chiller.
Water Quality Basics
Dissolved solids raise scaling risk and cut heat transfer. Keep TDS below 50 ppm and conductivity under 80 µS/cm. Use mixed‑bed deionizers and monitor pH monthly. A filming amine at 2 ppm coats copper and blocks corrosion.
Implementation advice
- Install 60‑mesh strainers upstream of the coil and clean them weekly. Fine oxide flakes often surface after the first month of a new install.
- Log conductivity once per shift for the first week after a coolant change; that early trend catches leaks into hard tap water.
- Use color‑coded quick couplers (blue in, red out) to keep operators from swapping hoses after maintenance.
Maintenance Made Simple
Check supply and return temperature spread daily. If ΔT rises, your condenser may be dirty or filters clogged. Inspect strainers each week and swap filter media monthly. Record compressor starts; more than six per hour often signals oversizing or a failing expansion valve.
Extra pointers
- Shoot the condenser coil with an IR thermometer. A 3 °C rise over ambient suggests dirt buildup.
- Add a vibration sensor to the compressor housing. An uptick can warn of imminent bearing failure long before a catastrophic stop.
- Schedule an annual coolant change or when lab analysis shows metals > 5 ppm or a big jump in chloride.
Energy Recovery and Savings
A chiller rejecting 20 kW of heat for one eight‑hour shift discards roughly 550,000 BTU. Run condenser water through a plate heat exchanger and pre‑heat domestic hot water. Or use it to temper fresh‑air make‑up in winter. Payback often lands under two years when electricity costs hover near €0.15 per kWh.
Final Tips
- Size from actual heat load. Measure first; guess later.
- Lock in a narrow temperature band. Variations drift your process.
- Protect water chemistry. Clean water saves coils and pumps.
- Log everything. Data spots problems before parts scrap out.
- Plan for redundancy. A small backup chiller or bypass loop can keep you running if a compressor fails.
Follow these basics and your induction process stays stable. You get repeatable parts, lower downtime, and a chiller that earns its keep year after year.