Industrial units have always been involved in the manufacturing, complex processing, or assembling of products. Cooling towers are one of the important components along with much other heavy equipment in an industrial unit. Here in this article, we will discuss the History of cooling towers, their working principle,  types, main parts, and maintenance in detail. So let’s begin our study.

History:-

After the development of the condensers in the nineteenth century, the cooling towers originated and improvements were made. These dynamic towers are widely used to discard the excess heat from the water during industrial operations into the atmosphere.

In the early 20th century, the electric power industry was rapidly blooming. The excess cooling generated by the generation of electric power led to the development of large structures cooling towers developed from wood, which led to the development of the modular, independently certified cooling towers of today. 

Cooling towers are widely used in oil refineries, petrochemical plants, thermal power plants, nuclear plants, food processing plants, natural gas plants etc.

 

Principle:-

Cooling tower systems work by using water to extract waste heat from a system and ejecting it into the atmosphere primarily through evaporation. The water is then distributed over the top of the cooling tower where air travels past the warm water causing a portion of the water to evaporate. The cooling tower nozzles spray the hot water into the “fill media” where there is maximum surface area and this leads to water-air contact. In this way, the water is cooled.

The methods may vary to some extent in different types of cooling towers but the basic method is the same.

Type of cooling tower:-


1. Crossflow cooling towers

In a crossflow tower, air flows horizontally through the cooling tower’s structure while hot water flows downward from distribution basins. Crossflow systems are some of the more expensive equipment types, but they are also some of the easiest to maintain. However, these cooling systems are more vulnerable to frost than others. Which makes it less efficient.


2. Counterflow cooling towers

In a counterflow system, the in-flowing air travels in a vertical path over the splash fill as the water streams down from the reservoir above. Counterflow systems are usually smaller than their crossflow counterparts.

 

1. Natural draft Hyperbolic cooling towers

A hyperbolic natural draft tower is dependable in its thermal performance. Airflow through this tower is produced by the density differential that exists between the heated air inside the stack and relatively cool atmospheric air outside the tower.

            Hyperbolic towers are more expensive than other types of cooling towers. Natural Draft cooling towers operate most effectively in areas of higher relative humidity, plants located in areas of average relative humidity areas find mechanical draft towers more applicable.

 

2. Forced draft cooling towers

Forced draft cooling towers use some type of mechanical pressure, as a fan system, to push air upward inside the tower. Forced draft means an exhaust fan placed at the base of the cooling tower which then causes overpressure. Both axial and centrifugal fans can be used. Forced draft cooling towers are characterized by high air entrance velocities and low exit velocities.

The advantages of a forced draft cooling tower are:

1. It is easy to produce turbulence, which is beneficial to heat transfer.

2. Lower operating costs.

3. The tube bundle can be checked and repaired from the upper part, and the operation is convenient.

The disadvantages are:

1. The air distribution is uneven.

2. The upper part of the tube bundle is open and easy to be affected by sunlight and rain.

 


3. Induced draft cooling towers

Induced draft implies an inlet fan placed on top of the cooling tower and the creation of low pressure. Axial fans are always used for this type of draft. Induced draft implies an inlet fan placed on top of the cooling tower and the creation of low pressure. Axial fans are always used for this type of draft

The advantages of an induced draft cooling tower are:

1. The airflow is evenly distributed;

2. Less noise;

3. The space under the tube bundle can be used.

The disadvantages of induced draft cooling tower are:

1. The fan is installed on the upper part of the tube bundle, which is affected by the high temperature of the tube bundle, which is not conducive to maintaining the fan;

2.The temperature of the air entering the fan after passing through the tube bundle is higher, so the power consumption of the induced air type is about 10% larger than that of the forced type fan;

3. The tube bundle needs to be repaired from the bottom, which is inconvenient to operate.



Cooling Tower Parts & Functions

Here is a list of the most common cooling tower parts that might need to be repair or replaced during the life of your cooling tower.


Cooling Tower Fill Media

Fill media is by far one of the most important cooling tower parts. It could be considered the middle man of the entire process. Many of today’s cooling towers use efficient plastic film fills or fill media that maximize the surface area for evaporative cooling processes. Water gets distributed onto the fill, which spreads into a thin film. This process increases the water-air interface and allows extra heat to evaporate at a fast pace.

Cooling Tower Instrumentation

Cooling Tower Instrumentation systems usually include Flow Meters For Cooling Tower Makeup Water, Blow Down Rate, Water Level Switches For Cold & Hot Water Basins, Thermocouples for Cold & Hot Water Measurement Of Temperature.

Cooling Tower Drift Eliminators

Cooling tower drift eliminators are parts of a cooling tower that are designed to remove droplets of water from the air and minimize the loss of process water. Drift eliminators cause the droplets and air to change direction suddenly. This process causes the water to become separated from the air and put back into the cooling tower.

Cooling Tower Nozzles

Cooling tower nozzles are most frequently used in crossflow cooling towers because they use gravity-flow distribution basins. With these types of systems, the water supply is raised to the distribution basins above the fill media and then flows down over the fill (by way of gravity) through the cooling tower nozzles in the basin floor.

Cooling Tower Fans

What are cooling tower fans used for? Cooling tower fans are used to force or push large amounts of air throughout the cooling tower. They must be built to withstand the corrosive effects in which the environment in that they operate. These fans are usually loud but there are certain types of low-sound cooling tower fans. Cooling tower fans are used in crossflow, counterflow, induced/forced draft cooling towers. Natural draft cooling towers don’t need fans because they use natural airflow and different processes that cool the water.

Fan Deck & Fan Cylinder

The deck of the fan is a supporting platform for the cylinders of the fan, which also makes an accessway to the fan and water distribution system.

Cooling Tower Fan Motor:

Petrochemical & Refinery cooling tower applications need explosion-proof fan motors to prevent leaks in heat exchangers. Fan motors need to be manufactured with Earth fault relay and overload relay protection systems.

Drive Shafts and Gearbox

What are cooling tower drive shafts used for? Driveshafts transmit power from the motor’s output shaft into the gear reducer’s input shaft. Driveshafts must also be corrosion resistant due to the harmful environment it which they operate. The driveshaft is the connecting link between the electric motor and the input shaft of the gearbox.

The different types of gearboxes include A series single reduction gearboxes, A series double reductions gearboxes, single reduction gearboxes, and double reduction gearboxes.

Automatic Water Level Controls

 Water Level Controls or float switches are manufactured to control water levels automatically. This helps ensure there is always the correct amount of water inside your storage tank. The level controls are typically used to automatically fill water and stop the fill once it reaches the adequate height

Piping For Water Distribution

Piping, for water distribution in a cooling tower, is buried underground and should be supported in-ground to prevent thrust loading in the cooling tower because of self weight and water pressure in the pipe.

Air Inlet Louvers

 Air inlet louvers or air intake louvers prohibit the sunlight from entering the basin, which prohibits algae growth and lowers chemical costs. These louvers also lower the amount of splash-out, which lowers the volume of water and chemical use. Also, you will experience easier basin removal and access. The air inlet louvers in counterflow towers can sometimes become scaly if they are not correctly maintained and cleaned. Scaled louvers lessen the amount of airflow which lowers the efficiency of the unit.

Distribution Valves

Distribution Valves regulate the flow of hot water to evenly distribute it in cells. The body of the valve in a distribution valve is made to withstand corrosive environments.

Cooling Tower Sealants & Coatings

Interior cooling tower coatings, or cooling tower sealants, help prevent corroding, leaking or rusting inside a cooling tower, while exterior coatings protect the outside of the cooling tower from corrosion and rust. Protecting all sides of your cooling tower helps prevent future problems and costly repair.


Maintenance of cooling tower

Cooling towers being the most robust industrial units need to be maintained. This maintenance can be achieved in many ways. The strainer system must be implemented to collect all the debris and contaminants.

Clogging can be prevented by cleaning the nozzles. The nozzles must be placed inaccessible areas. The cooling tower can work properly when water treatment options are ensured. This may include water modeling, green chemical usage, filtration, etc.

There should be the deep cleaning of the cooling tower which can be done with the help of a cleaning chemical that circulates throughout the tower. Moreover, the components like fans, motors, and belts should be inspected and cleaned when required. The electrical components should also be inspected.


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