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How Flow Rate Impacts Cooling Tower Design

A. Cross-Sectional Area (Air-Water Contact Zone)

• Higher flow rate → Larger fill area needed.
• Formula:
  • Typical Loading Rates:
    • Film Fill: 15–25 m³/hr·m²
    • Splash Fill: 10–15 m³/hr·m²

B. Fan & Motor Sizing

• Higher flow = Larger fan diameter & motor HP.
• Example:
  • 100 m³/hr → 1.5–2 HP fan
  • 500 m³/hr → 10–15 HP fan

C. Basin Volume

• Must hold 3–5 mins of water flow (for pump suction stability).
• Formula:

Basin Capacity (m³)=Flow Rate (m³/hr)×560Basin Capacity (m³)=60Flow Rate (m³/hr)×5​

3. Cooling Tower Sizing Example

Given:

• Flow Rate: 300 m³/hr
• Heat Load: 1000 TR (Refrigeration Tons)
• Approach: 5°C
• Fill Type: Film fill (Loading rate = 20 m³/hr·m²)

Calculations:

1. Fill Area Required = 300 / 20 = 15 m²
2. Basin Capacity = (300 × 5) / 60 = 25 m³
3. Fan Size ≈ 15–20 HP (based on airflow needs)

Estimated Tower Dimensions: ~ 6m (L) x 5m (W) x 8m (H)