Cooling Tower, its components, working principle and types.

Definition of Cooling Tower:-

A cooling tower is a special type of heat eliminator used to cool the hot water for re-use. the water gets overheated when it undergoes industrial processes and passes through equipment.

What is Evaporative Cooling?

To understand Evaporative Cooling take this example, when you come out after taking shower you feel that your body is getting gradually cold. Have you ever thought about why this is? When your body comes in contact with atmospheric fresh air, it lowers the temperature of water particles on your body evaporation leaving a cold impact behind. This is called Evaporative Cooling.

Working Principle of Cooling Tower:-

Different cooling towers can be used for various domestic or industrial purpose but all are bound to follow the exact same working principle that is Evaporative cooling. The cooling process is based on the action of two things:

·         Hot Water

·         Atmospheric Air

Hot Water:-       

There is always a base or lake for the storage of hot water, bypassing several processes. For cooling, it is first made to move up by pump to the header from where it is injected into the cooling tower through the specified inlet. There are spraying nozzles soon after the bottom of the inlet. They spray the water to increase its surface area. Then the water comes across the PVC fillings which reduces the speed of water movement.

Atmospheric Air:-

Air is moved upward from the bottom (direction and source depends upon the type of cooling tower used) and comes in contact with hot water particles.

v  When both water and air particles meet, evaporative cooling occurs due to the increased surface area and decreased velocity of the water particles. Both of these factors also help in causing a longer interaction. In the end, the cold water is drained out by the outlet and hot air is released into the environment.

Basic Components of Cooling Tower:-

§  Eliminator- it does not allow water particles to escape; only hot air can pass through it.

§  Spray Nozzles-they sprinkle water through nozzles for increasing surface area to enhance the rate of evaporation.

§  PVC fillings- it reduces the speed of hot water particles.

§  Mesh- atmospheric air essentially contains dust particles mixed with it, the mesh is used to get rid-off them.

§  Float Valve- for the maintenance of water level.

§  Bleed Valve- control and adjust the pH of water by accessing the concentrations of minerals and salts dissolved.

§  Body- the outer surface is made up of FRP (Fiber Reinforced Plastic) which protects the internal infrastructure from external agents.

Factors affecting the efficiency of Cooling Tower:-

1.       Size and height of Cooling Tower.

2.       The temperature of the Air.

3.       How humid is the air which is to be used?

4.       The velocity of air particles inserted.

5.       Accessibility of air particles to all parts of the Cooling Tower.

 

 

 

Types of Cooling Towers:-

Cooling Towers are generally classified based on the Air-Flow method they are using.  The common types based on air-flow generation method are Natural Draught, Mechanical Draught, Cross-Flow and Counter-Flow.

Here we will go through each to get concept and understand the differences between them.

 

1.   Natural Draught Cooling Tower:-

Natural Draught Cooling Tower uses the tall shape and hyperbolic design to induce airflow into the building.

 

2.   Mechanical Draught Cooling Tower:-

Mechanical Draught cooling tower tend to use the source for propelling the air to be circulated inside for cooling purposes.

There are two main types of Mechanical Draught Cooling tower stated below:

ü Induced Draught Cooling Towers:-

In induced draft towers the fans are located at the discharge (at the top) and pull the air through the tower. Air enters the sides of the tower at low velocity through large openings and passes through the fill, whereas the hot humid air is exhausted to the atmosphere through the ventilator. This maintains the tower at a negative pressure that reduces leakage.

ü Forced Draught Cooling Tower:-

In the forced draft cooling towers the blower type fans are mounted on the lower side of the tower. Though these fans consume less power as they operate in cooler air, such a design has the disadvantages of air distribution problems, leakages and recirculation of the hot and moist air back to the tower.

Advantages of I.D Cooling tower over F.D Cooling Tower:-

        I.            Extremely efficient compared to forced draft cooling tower.

      II.            Employs 50% less energy while comparing to forced draft design.

    III.            Contains a fan located on the top, which drives the air via the fills.

    IV.            An inlet fan is placed on the top of the cooling tower, which creates low pressure.

There are two basic types of I.D Cooling Tower one is cross-flow in which the air is supplied horizontally and water provided is vertically sprayed so both are perpendicular to each other whereas in the case of counter-flow the air blown is vertically upward and the water is thrown vertically downward so both are opposite to each other.

Affect of Cooling Tower on Ecosystem:-

Without cooling pinnacle and utilizing once-through water for the point of cooling, it would require an enormous measure of water and warmed water would need to be constantly gotten back to the stream, lake or sea, from which it was again gotten and resupplied to the force plant. In such a manner, releasing warm water devoured in immense force plants may build the temperature of the getting lake or stream and change the nearby environment. The raised water temperatures can hurt oceanic creatures, murder fish and other living animals. Then again, cooling towers discharge a lot of Hot water into the environment all things considered, which spreads by wind over a lot, bigger area than that of heated water can disperse neighbourhood waters. Sadly, oil processing plants additionally devour extremely enormous the measure of water in the cooling tower just as coal-terminated also, thermal energy stations. Situating in waterfront territories and utilizing once-through seawater, cooling towers ought to be analyzed for release water condition to stay away from natural contamination.

 Bottom Line:-

 The basic characteristics of various types of cooling towers were analyzed using literature references to reveal differences of cooling towers in the term of structure, application and cooling principles. It was discussed that cooling towers are an essential component of power plants like nuclear power stations as well as petroleum refineries, petrochemical plants and food processing plants. The working principles of natural draft and mechanical draft cooling towers were compared. Dry and wet types of cooling towers were also reviewed in this study. Finally, fluent software as a CFD program was employed to simulate a sample cooling tower and as a result, major contours of the simulation were provided in this work.