Double‑wall Tube‑in‑tube Finned Coil for Hospital Cleanroom

Hospital clean AHU (operating room ICU、 Negative pressure isolation ward, PCR laboratory, biosafety BSL-2/3) core risk points:

1. Prevention of cross contamination/nosocomial infection : If the coil is perforated, frozen water, ethylene glycol, and pipeline rust can directly mix into the clean air supply, causing ward contamination and medical accidents; Ordinary single-walled coils are potential hazards.

2. High humidity condensing environment : Continuous condensation occurs under surface cooling conditions, and the coil remains damp for a long time, which is prone to corrosion and the growth of microorganisms; The condensate tray requires 304 stainless steel, rounded corners, and no dead water dead corners.

3. Negative pressure system *: The AHU in the isolation ward is under negative pressure. When the coil is perforated, the water side medium is more easily sucked into the supply air duct by negative pressure.

4. Continuous operation is required and shutdown is not allowed . The equipment needs to be repairable and the tube bundle can be removed.

5. It is necessary to meet ASHRAE-170 and the technical specifications for clean operating department buildings in hospitals.

Core safety logic of casing fins (double wall fins)

-Internal pipe: cold water/hot water/ethylene glycol (pressure 1.0-1.6 MPa)

-Circular interlayer: safety leakage chamber, leading out leak detection port (visible+can be connected to sensor alarm)

-Welding fins on the outer wall of the jacket tube, clean air only comes into contact with the jacket tube and fins

>Corrosion and damage of the inner tube → water leakage into the interlayer, alarm prompt, will not enter the clean air supply ; The outer sleeve will only leak if it is damaged again, with a double-layer barrier.

Scenario 1: High risk clean AHU surface cooling/heating coils (operating room, ICU negative pressure isolation ward, most importantly)

-Replace ordinary Chilled Water/Hot Water coils; AHU processes clean fresh air and circulating air; Realize cooling, dehumidification, and reheating.

-Operating conditions: chilled water at 7-12 ℃; Hot water 50-70 ℃; The air is clean air that has undergone initial and intermediate filtration.

-Advantage: Eliminate the safety hazards of ethylene glycol and frozen water leakage pollution in clean air supply.

Scenario 2: BSL-2/3 air conditioning unit coil in biosafety laboratory

-Negative pressure operation, strict prohibition on medium leakage entering the air supply; Priority should be given to using double wall coils with casing and fins.

-The interlayer leak detection signal is connected to the building BA system, and an alarm is triggered to remind maintenance personnel to replace the tube bundle.

Scenario 3: Recovery of waste heat from hospital exhaust (PCR, laboratory exhaust)

-Exhaust air containing disinfectant aerosols and chemical volatiles, passing through the outer fins of the sleeve tube; Preheating fresh air by recovering heat from circulating water in the inner pipe;

-Double layered casing prevents water circulation medium from entering the exhaust system.

Scenario 4: Dry coil working condition (clean interlayer FFU system)

-Operating under dry conditions, the water temperature is higher than the dew point of the air, and no condensation is produced; The sleeve fins serve as sensible cooling coils to eliminate the risk of water leakage.