A cooling tower is a large industrial equipment that cools water by removing heat through evaporation and heat transfer. Cooling towers are used in many applications, including: Power plants, Oil refineries, Petrochemical, Metallurgy, chemical plants and HVAC systems for building cooling. If you look down from a high-rise building, you might observe a square structure equipped with large fans on top. That’s what we call a water cooling tower.
What is the purpose of a Cooling Tower?
A Cooling tower’s purpose is to cool the hot water originating from the condenser. It is a huge heat exchanger which expels building heat into the atmosphere and returns colder water to the system.
Types of Cooling Tower
The different types of Cooling towers are categorized based on draft type (natural or mechanical) and airflow direction (counter or cross). The classification is explained below:
1. Natural Draft Cooling Towers
These types of cooling towers are commonly found in large power plants and industries with continuous water flow, and operate by removing excess heat by way of rising hot air that is then released into the atmosphere. The Natural Draft Cooling Towers are often featuring a hyperbolic shape, relying solely on the difference in air densities to induce airflow, eliminating the need for mechanical fans. While cost-effective and efficient, they are limited to outdoor installation and may exhibit lower reliability due to susceptibility to ambient conditions like wind and temperature fluctuations.
2. Mechanical Draft Cooling Towers
Mechanical draft cooling towers utilize either single or multiple fans to drive airflow through the tower. Unlike natural draft towers, they offer greater reliability and stability as airflow can be adjusted based on the cooling demand. Further classification of mechanical draft towers includes forced or induced draft configurations.
3. Induced Mechanical Draft Cooling Towers (Cross flow and Counterflow Towers)
In Induced draft cooling towers fans are positioned at the top, drawing air in through the intake louvers at the tower’s bottom or sides. This design minimizes recirculation due to low entrance and high exit air velocities. The Induced Draft Cooling Towers are widely favored in industrial settings for their stable performance.
Sub classification of Induced Mechanical Draft Cooling Towers :
– Crossflow Configuration
In Cross-flow cooling tower configuration air flows horizontally through the fill material while water falls downward, i.e. Air-Water contact is at 900 . A distribution basin ensures that hot water is evenly distributed over the fill using gravity and nozzles. Unlike other systems, cross-flow towers don’t need pressurized spraying, making maintenance simpler. The distribution system can be divided into sections, allowing for independent servicing and reducing operational downtime.
– Counterflow Configuration
In a counterflow cooling tower configuration, the system directs process water into a sealed header box. It then distributes the water through branch arms and nozzles, creating a pressurized water distribution system where air-water contact occurs at 180 degrees. Unlike other cooling towers, in counterflow designs, water flows downward while air moves upward, optimizing heat exchange. This arrangement enhances efficiency by minimizing water usage and maximizing cooling capacity. Additionally, counterflow towers typically have a smaller footprint compared to other configurations, making them suitable for space-constrained environments.
4. Forced Mechanical Draft Cooling Towers
This type of cooling tower operates similarly to induced draft, but with one key difference: the fan sits at the tower’s base or side, pushing air inwards.
How Does a Cooling Tower System Work?
A cooling tower effectively distributes heat produced by air conditioning equipment or industrial processes. As Tons of hot water flows into the cooling tower, it is recirculated and exposed to cool, dry air. Evaporative cooling removes heat from the water as it evaporates into the surrounding atmosphere. This evaporation process occurs when water is sprayed as minute droplets across the fill material, increasing surface area and allowing for increased heat loss.
A fan sits on top of the cooling tower, which takes in air from below and expels it upwards in the opposite direction of the heated condenser water at the top. As the air rises, it removes heat by evaporating water from the cooling tower, effectively cooling the recirculating water. This cycle is repeated indefinitely, ensuring efficient cooling of equipment or processes.
Basic Cooling Tower Terminologies:
- Bleed off – Also known as blowdown, is essential for maintaining the dissolved solids concentration in tower water within acceptable limits by discharging circulating water waste.
- Biocides – Plays a crucial role in controlling microbial populations by eliminating troublesome microbes.
- Cooling range – Refers to the temperature difference between incoming and outgoing cooling tower water.
- Cycles of concentration – It measures water purity by comparing the dissolved solids in makeup water to those concentrated through evaporation. This helps determine how efficiently water is being used and when it needs to be replaced to maintain system performance.
- Drift – Refers to water carried by airflow and released into the atmosphere, excluding water lost through evaporation. Effective cooling tower design can reduce drift loss.
- Heat exchangers – Facilitate heat transfer between substances, crucial for cooling tower operation.
- Makeup water – It’s the amount of water necessary to replenish losses from bleed-off, drift, and evaporation.
- Pumping head – Indicates the pressure required to circulate water through the system.
- Wet bulb temperature – The lowest temperature achievable through evaporation, plays a crucial role in cooling tower selection and design. It is measured using a psychrometer.
How to Select the Right Cooling Tower?
Selecting the right cooling tower involves considering factors like cooling load, water quality, space constraints, and environmental conditions. Check out our FRP Cooling towers & Contact us for expert guidance or a quote on a new cooling tower.
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