- Cooling Tower Definition: Cooling towers are structures that help cool process water by removing heat through evaporation.
- Cooling Tower Material of Construction: Common materials include fiberglass, galvanized steel, stainless steel, concrete, and FRP, each offering different benefits.
- Replaceable Components: These include draft fans, packing materials, hot water distribution systems, louvers, and drift eliminators, which are essential for efficient operation.
- Non-Replaceable Components: Permanent structures like the cold water basin are crucial for collecting and recirculating cooled water.
- Packing Materials: Enhance cooling efficiency by increasing the water surface area for better heat transfer.
Various materials are used to construct cooling tower structures. Fiberglass is often used for package cooling towers. For field-erected cooling towers, materials like steel, fiberglass, redwood, and concrete are chosen based on project location and client preference.
Plus and minuses of each cooling tower material is given below:
Wood:
Redwood was commonly used for small cooling towers in the 1970s and 1980s. Nowadays, due to its scarcity, wood is rarely used in cooling towers.
Following are the drawbacks when wood is used as a material:
- Durability: Wood is considered as less durable during operation and also having less life compared to other materials.
- Drift Losses: are more i.e over 1%.
- Signification: Problem of wood eating is more and requires pH adjustment.
- Area Requirement: is more thus having a larger foot prints compared to others.
- Algae: serious problem of algae formation.
- Heavy structure: Wood structure are more heavier than the other cooling tower materials thus increases the civil cost.
Galvanized Steel:
It is the most common construction material for cooling towers. G-235 hot-dipped-galvanized steel is suitable from corrosion resistance point of view and also having good structural strength.
Stainless Steel:
Further development and improvement in the cooling tower material leads to stainless steel, which is superior to G-235.
Stainless steel 304 cooling tower material is used and recommended for cooling towers installed in the highly corrosive environment.
Concrete Towers:
Concrete cooling towers are usually very large towers.
Salient features of concrete towers are:
- Long Life: life of the towers are over 38-40 years.
- Erection Time: these are field erected towers and requires more time in completion.
- Expensive towers: these towers are very expensive which is fairly compensated by its long life.
Fibre Reinforced Plastics (FRP) Towers:
Application of FRP towers are growing very fast and more and more process plants are replacing their old wooden cooling towers with FRP.
Salient features of FRP cooling towers are:
- Light in weight
- Having good defiant against chemical water, thus operation of it is possible in wide pH range.
- FRP towers are fire resistant, thus need not require fire protection system.
- These towers requires less erection time and also having cost advantage with respect to others cooling towers.
Components of Cooling Tower
Life of a well maintained cooling towers ranges between 20 to 25 years approximately. There are two type of important components in a cooling:
Replaceable Components like
- Air moving component (draft fans)
- Packing materials (Fills)
- Hot water distribution system
- Louvers
- Drift eliminators
Non Replaceable Components/Permanent Structure like
- Cold Water Basin
Description of the major components of cooling tower and their functions are given below:
Packing Materials Coling Tower
Is vital component of a cooling towers, as it enhances the cooling effective of the cooling tower by providing Spalsh Fills and Film fills.
Splash Fills:
Towers having horizontal and vertical staggered patterns to splash the hot water falling down from the top of the tower distribution deck. Splash causing the hot water to get divided in fine water droplets and increases its surface area of water between air and water.
Film Fills :
These are plastic corrugated sheets that are joined together to give a honeycombed appearance. Material used for film fill are PVC, Polypropylene.
Cooling Tower Hot Water Distribution System
It is for distributing hot circulating water inside the cooling towers to cool the hot process water. It includes distributing basin, headers, distributing arms, spray nozzles, flow regulating valves.
Cooling Tower Cold Water Basin
The cold water basin at the bottom of the tower collects cooled water and supplies it to the circulating water pumps. Its capacity should be three times the circulating water flow rate in gallons per minute (gpm).
Cooling Tower Fan
Fans are used in induced draft cooling towers. Commonly used blade material are FRP, Aluminum and hot-dipped-galvanized steel.
Louvers
Function of louver in cross flow cooling tower are
- To equally distribute the air flow to the fills.
- It helps in retaining the water inside the tower.
Louvers are not required in counter flow cooling tower.
Drift Eliminators
Function of it is to remove the water droplet entrained in the hot air going out of the cooling towers. It reduces the drift to less than 0.0005% of the circulating water. It is made up of PVC.
