Cooling towers use air-to-water contact (either direct or indirect) to dissipate heat and provide reusable cooling water for circulation. When selecting a cooling tower, several key factors must be considered to ensure efficient performance and seamless integration into an existing system.
1. Key Considerations for Selection
Before purchasing or selecting a cooling tower, the following details must be clarified:
- Specify the exact model or the required flow rate (m³/h).
- Identify the cooling application, whether it’s for industrial equipment or an HVAC system.
- Clarify on-site conditions such as space availability and presence of a circulating water tank.
- List spare parts and additional accessories required.
- Specify any extreme working conditions that could affect selection, such as high humidity or corrosive environments.
- Determine the inlet water temperature to choose between standard, medium-temperature, or high-temperature models.
- Consider noise requirements, selecting between crossflow or counterflow designs.
- Calculate cooling tower flow—it should be 1.2 to 1.25 times the cooling water flow of the chiller or refrigeration unit.
- For multi-unit setups, use identical models for consistency.
2. Important Factors to Consider
- Material Durability: The structure should be corrosion-resistant, long-lasting, and precisely assembled.
- Water Distribution: Ensure even water distribution to prevent blockages and uneven cooling.
- Packing Type: Must be suited to water quality and temperature requirements.
- Fan Efficiency: Should provide stable operation with minimal noise and adjustable blade angles.
- Low Energy Consumption: Preferably lightweight and cost-effective for medium to small units.
- Installation Location:
- Avoid placing near heat sources, smoke exhaust, or chemical storage areas.
- Maintain safe distances from buildings to meet fire and maintenance standards.
- Water Pipe Configurations: Can be installed at 90°, 180°, or 270° rotations.
- Cold Weather Adaptability: If operating in temperatures below -10°C, anti-freezing measures must be taken.
- Water Quality Requirements:
- Turbidity should be ≤50mg/L, short-term limit ≤100mg/L.
- Must be free of oil contaminants and large particles.
- Consider algae control and water treatment if needed.
- Component Handling:
- Avoid stacking heavy objects on parts during transport.
- Keep away from fire hazards and avoid exposure to sunlight.
- Installation Safety:
- Avoid open flames, welding, and fireworks near the unit.
- Multi-Tower Setup:
- Round towers should maintain a minimum 0.5x tower diameter spacing.
- Crossflow and counterflow towers can be installed side by side.
- Pump Compatibility: Ensure correct flow and pressure matching with the cooling tower.
3. Cooling Tower Performance Indicators
To assess the efficiency of a cooling tower, the following key performance indicators are used:
Cooling Water Temperature Difference (∆t)
The difference between the inlet (t1) and outlet (t2) water temperatures:
[
∆t = t1 – t2
]
- A higher ∆t indicates better cooling efficiency.
- If inlet temperature (t1) is too high, even a large ∆t may not cool water to the required level.
Cooling Approach (∆t’)
The difference between the outlet water temperature (t2) and the ambient wet-bulb temperature (T):
[
∆t’ = t2 – T
]
- Smaller ∆t’ values indicate better performance.
- ∆t’ can never be zero, as water cannot cool below the wet-bulb temperature.
Spray Density (q)
The amount of water cooled per square meter of tower effective surface area per hour:
[
q = \frac{Q}{F}
]
Where:
- Q = Cooling tower flow rate (m³/h)
- F = Effective water spray area (㎡)
By following these selection criteria and performance indicators, cooling towers can be optimized for maximum efficiency, longevity, and energy savings.