A Cooling Tower is a heat rejection device used to remove excess heat from water by cooling it through contact with air. It is commonly used in power plants, HVAC systems, refineries, and industries.

Cooling towers cool hot water from condensers or industrial processes and recirculate it back into the system.

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Working Principle

1. Hot water enters the cooling tower.
2. Water is distributed over fill material.
3. Air flows upward/downward through tower.
4. A small portion of water evaporates.
5. Heat is removed from remaining water.
6. Cooled water collects in basin and returns to system.

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Main Components

• Fan
• Fill Media
• Drift Eliminator
• Water Distribution System
• Cold Water Basin
• Pump
• Louvers
• Structure / Casing

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Types of Cooling Towers

1. Natural Draft Cooling Tower

• Uses natural air circulation.

2. Mechanical Draft Cooling Tower

• Uses fans for air movement.

a) Induced Draft

b) Forced Draft

3. Crossflow Cooling Tower

• Air flows horizontally.

4. Counterflow Cooling Tower

• Air flows opposite to water flow.

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Important Formulas for Calculation

1. Cooling Range

$$Range = T_{hot} – T_{cold}$$Range=Thot​−Tcold​

Where:

• $T_{hot}$Thot​ = Hot water inlet temperature
• $T_{cold}$Tcold​ = Cold water outlet temperature

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2. Approach

$$Approach = T_{cold} – T_{wb}$$Approach=Tcold​−Twb​

Where:

• $T_{wb}$Twb​ = Wet bulb temperature

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3. Cooling Tower Efficiency

$$Efficiency = \frac{Range}{Range + Approach} \times 100$$Efficiency=Range+ApproachRange​×100

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4. Heat Removed

$$Q = m \times Cp \times (T_{hot}-T_{cold})$$Q=m×Cp×(Thot​−Tcold​)

Where:

• $Q$Q = Heat removed (kJ/hr)
• $m$m = Water flow rate
• $Cp$Cp = Specific heat of water

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5. Evaporation Loss

$$Evaporation Loss = 0.001 \times Flow \times Range$$EvaporationLoss=0.001×Flow×Range

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6. Blowdown

$$Blowdown = \frac{Evaporation Loss}{COC – 1}$$Blowdown=COC−1EvaporationLoss​

Where:

• COC = Cycles of concentration

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Applications

• Thermal Power Plants
• HVAC Systems
• Chemical Plants
• Steel Industries
• Oil Refineries
• Plastic Industries
• Food Processing Plants

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Maintenance of Cooling Tower

Daily Maintenance

• Check fan operation
• Check water level
• Observe unusual noise/vibration

Weekly Maintenance

• Clean basin
• Check nozzles
• Inspect belts and motors

Monthly Maintenance

• Water treatment check
• Remove scale deposits
• Lubricate bearings

Yearly Maintenance

• Replace damaged fill media
• Structural inspection
• Motor servicing

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Common Problems

• Scaling
• Corrosion
• Algae growth
• Fan imbalance
• Water leakage

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Advantages

• Saves water by recirculation
• Reduces plant temperature
• Energy efficient
• Low operating cost

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Cooling Tower Performance Chart

Parameter	Formula
Range	Hot Temp – Cold Temp
Approach	Cold Temp – Wet Bulb Temp
Efficiency	Range / (Range + Approach) ×100
Heat Removed	m × Cp × ΔT
Blowdown	Evaporation / (COC-1)

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Cooling Tower Diagram

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Conclusion

Cooling towers are essential for industrial heat rejection systems. Proper calculations and maintenance increase efficiency, reduce water losses, and extend equipment life.