Cooling Tower Selection

Tower Configuration

Counter-flow: highest thermal efficiency

Capacity & Design Parameters

Chiller capacity + compressor work (approx. Chiller kW x 1.25)
Standard allowance for fouling and hot days: 15%

Water Side Temperatures

From Chiller condenser outlet. Typically 35°C
To Chiller condenser inlet. Standard Euro/US: 29.4°C

Ambient Air Conditions

CRITICAL limit. Tower LWT cannot go below this

Aerodynamics & Fans

Water saving control index. Standard range: 3-5

Water Losses Configuration

Modern: 0.001-0.01%
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Cooling Tower Selection

Cooling towers reject waste heat to atmosphere through evaporative cooling. Water is distributed over fill material while air flows through the tower, causing a small portion of water to evaporate and cool the remainder. The Merkel equation relates the heat transfer to the air's enthalpy change and the tower's transfer characteristics. Key design parameters are the cooling range (hot-cold water ΔT) and approach (cold water - wet bulb ΔT). A smaller approach requires a larger, more expensive tower.

Key Points:
  • Cooling Range: Typically 5°C (35°C in / 30°C out) for HVAC applications
  • Approach: Minimum 2.8°C (5°F) for standard towers, 1.7°C (3°F) for premium towers
  • Wet-bulb temperature is the critical design parameter - towers are sized for 0.4% annual value
  • L/G ratio (water/air mass flow) typically 0.8-1.2 for counterflow, 1.2-1.5 for crossflow
  • Evaporation loss: ~1% of circulation per 5°C of cooling range
  • Blowdown required to prevent scale buildup - depends on makeup water quality
  • Fan power increases with tower height and air flow resistance through fill
Calculation Steps:
  1. Enter all required parameters
  2. Click "Update Calculation"
  3. Review results and analysis
Formula Variables:
Q Heat Rejection (kW)
ṁw Water Mass Flow (kg/s)
ṁa Air Mass Flow (kg/s)
L/G Liquid to Gas Ratio (kg/kg)
NTU Number of Transfer Units (-)
KaV/L Tower Characteristic (-)
Range Cooling Range (°C)
Approach Approach to Wet Bulb (°C)