What Is The Fan Stack Cooling Tower​

A fan stack in a cooling tower is the vertical cylindrical (or slightly flared) structure installed above the fan. It plays a major role in airflow efficiency and drift control.

What a fan stack coling tower does

1. Guides airflow smoothly

  * Straightens and directs air leaving the fan

  * Reduces turbulence and recirculation

2. Improves fan efficiency

  * Converts fan discharge velocity into useful airflow

  * Increases effective air volume (CFM) without increasing motor power

3. Reduces energy consumption

  * Lower system resistance = less fan horsepower required

4. Controls air discharge pattern

  * Discharges air vertically to prevent hot, moist air from re-entering the tower (recirculation)

5. Supports drift eliminator performance

  * Stable airflow helps minimize water droplet carryover

 Typical fan stack design

* Shape: Cylindrical or bell-mouth inlet

* Height: Usually 0.3–1.0 × fan diameter (varies by OEM)

* Diameter: Slightly larger than fan diameter

* Materials:

 * FRP (fiberglass-reinforced plastic) – most common

 * HDPE or PP (smaller towers)

 * Galvanized or stainless steel (older or special-duty towers)

Fan Stack Location in cooling tower (top-mounted fan)

```

  ↑ Air discharge

┌───────────────┐

│   Fan Stack   │

├───────────────┤

│      Fan      │

├───────────────┤

│ Drift Elimin. │

│     Fill      │

│   Spray Zone  │

```

Common problems with fan stacks

* Cracks or delamination (FRP stacks)

* Loose bolting causing vibration

* Incorrect height or diameter reducing airflow

* Air leakage at stack-to-deck joint

 Fan stack vs fan cylinder

* Fan stack: Above the fan (discharge side)

* Fan cylinder (or shroud): Around or below the fan (inlet side)

Both are critical for proper aerodynamic performance.