Run-Around Coil Systems for Contaminated and Hazardous Exhaust

What makes exhaust hazardous

Some industrial exhausts carry solvents, fumes, or particulates that must not re-enter the building. The recovery device has to extract heat without any path for that exhaust to reach the supply air. That rules out any shared-matrix technology, including the rotary wheel.

How a run-around coil works

Two finned coils sit in the two airstreams and are joined by a sealed pipe loop with water or glycol. The exhaust-side coil transfers heat to the fluid; the fluid flows to the supply-side coil and warms the incoming air. The air never crosses; only the fluid moves. Because the loop is sealed, containment is absolute and maintenance is confined to the coil faces. See Run-Around Coil and Desiccant Recovery and Separated Recovery Applications.

Where it fits

Run-around coils suit paint booths, chemical plants, laboratories, pharmaceutical suites, and any exhaust classified as contaminated. They also serve as a frost-free pre-heater ahead of a plate exchanger when the exhaust is clean but very cold.

Trade-offs

Expect 50 to 65 percent sensible effectiveness, lower than a wheel, plus a small pump and a freeze-protected fluid. For hazardous duty that trade is non-negotiable: safety beats a few points of effectiveness. Size the loop for the temperature lift and keep the glycol above its freeze point.

Run-around vs heat pipe vs plate

Heat pipe also separates streams with no pump, but only across a wall in one assembly and within tilt limits. Plate separates streams but can foul or ice with dirty cold exhaust. Run-around coil separates streams across any distance and is easiest to service. The choice depends on layout and service access; our selection guide frames it.

Bottom line

For contaminated or hazardous exhaust, recover energy with a run-around coil: streams fully separate, no mixing, serviceable. Never use a wheel. Contact Qiyu engineering (15753355505) for a contained-recovery package.