A cooling tower is a crucial heat removal device that uses water and air to transfer process waste heat into the atmosphere. Actually, it is a special type of heat exchanger that decreases the temperature of the hot water.
A small volume of water evaporates from this device during the working process reducing the temperature of process waste water that’s being circulated throughout the cooling tower. As a result, process heat is easily removed into the atmosphere through the cooling of a coolant stream, usually a water stream, to a lower temperature. This device is very suitable to remove process heat and cool the working fluid to near the wet-bulb air temperature.
This device is very popular for heating, ventilation, air conditioning, and industrial purposes. It helps to provide a cost-effective and energy-efficient operation of systems. Heating, ventilation, and air conditioning (HVAC) systems are used very much in large office buildings, schools, and hospitals. Industrial cooling towers are large in size and used in thermal power plants, petroleum refineries, fertilizer industries, petrochemical plants, natural gas processing plants, food processing plants, and other industrial facilities.
Cooling Tower Definition
A cooling tower is very essential cost-effective device to transfer process waste water heat into the atmosphere. The process water or condenser water flows directly over the surface of this device. A small amount of water evaporated due to the introduction of air into this device and cooling the remaining water.
There are various sizes of this device depending on the fields of applications. The length of this device can be up to 200 meters (660 ft) tall and 100 meters (330 ft) in diameter when it has a hyperboloid structure. The rectangular shape of this tower can be over 40 meters (130 ft) tall and 80 meters (260 ft) long.
Cooling Tower Working Principle
The input material of this device is hot water from the top position. It flows through a pipe which is generally made to pass through the spray nozzles. The hot water flows through this device as droplets. As a result, the surface area of hot water increases when water falls down due to the influence of gravity. The air must be flown as the input material in the equipment through the bottom of the cooling tower.
The hot water falls on the fill materials which are called packings or baffles. These fill materials help to increase the surface area for the heat transfer operation. When the hot water and air come in contact, evaporative cooling takes place to reduce the temperature of hot water and increase in temperature of the air.
Cooling Tower Types
There are various types of this equipment namely atmospheric towers, natural draft towers, and mechanical draft towers.
Air Draft cooling towers are classified as Atmospheric towers, Natural draft towers, and Mechanical draft towers. The Mechanical draft towers are two types namely forced draft type and induced draft type.
Atmospheric Cooling Tower
It is a very simple type that consists of a rectangular chamber. This chamber has louvered walls on the opposite end that act as the barrier for splash out and sunlight. It also gives a direction to the flowing wind. The atmospheric air comes in contact with this tower depending on the speed of the wind guided by the louvers.
The hot water and air come in contact with the fill material because this tower is filled with the fill material. The fill materials are cheap but inefficient based on their performance is largely conducted by wind velocity and direction.
Natural Draft Cooling Tower
It is known as a hyperbolic tower which is constructed by the concrete mixture. The natural air can move easily through this tower. It helps to remove the waste water heat by way of rising hot air that is then released into the atmosphere. This tower is tall and contains a hyperbolic shape to induce proper airflow. It is used in large power plants and industries with infinite cooling water flow.
The air enters into this device from the bottom and the water gets splashed. The water molecule shape turns into droplets when it touches battens.
Forced Draft Cooling Tower
This equipment consists of fans to move air inside this tower. The fans are situated at the bottom position to push the air inside the tower. A forced mechanism is created in this tower which makes it more effective than the natural draft tower. The large fans create a motion of the air to become non-uniform while it passes through the fill material. This device may pick up the exit air from outside and push it back inside the tower which is a demerit of this device. It hampers the efficiency of the tower due to the increases in inlet air saturation level.
Induced Draft Cooling Tower
This tower is designed in such a way that it can remove the re-circulation effect. The fans in this tower are located at the top position. The air inlet position is located at the bottom of the tower. Suction is created at the bottom position during the operation of fans. This cooling tower is highly efficient as it uses 40% to up to 80% less energy compared to a forced draft tower.
Counterflow Cooling Tower
The design of this tower is made to move the air upward direction and the counter-current, with hot water, falls downward to cool the air which helps to achieve the maximum performance out of each plan area and reduces the pump head requirements.
Cross-flow Cooling Tower
It allows the air to flow horizontal direction through the fill materials. Then it flow the tower inlet into an open plenum area. The distribution basin circulates the hot water downward direction. Fans and motors of this equipment help to drive the weather-proofing conditions against moisture.
Cooling Tower Parts and Functions
There consists of various parts in the cooling tower like the basin, tower framework, fan deck, casing, louvers, and various components which discussions are given below:
Fill
It is called a wet deck or surface. It increases the contact surface area and contact time between the air and the water.
Distribution System
This system uses a gravity-flow distribution where the water can be smoothly distributed at an elevation above the fill.
Drift Eliminators
It prevents the escape of water droplets creating a sudden change in the path of the air stream.
Louvers
It serves as a block for water splash-out, noise, and debris. It locates above the cold water basin, at the bottom of the panel.
Casing
This part provides housing and transmits loads to the tower frame.
Fan, Motor, Driveshaft, and Speed Reducer
The air is transferred easily by having fans and the driver material is the motor. The motor in this equipment produces torque which can be transferred by the driveshaft to the fan or to a gearbox.
Fan Stack
It is also called the fan cylinder or fan cover which increases the efficiency of the fan. This work can be performed by a well-shaped air inlet to create smooth airflow into the fan.
Fan Deck
It supports the fan cylinders and acts as a structural member for transferring loads throughout the tower frame.
Valves
Valves are essential for controlling the water level inside the cooling tower. There are various types of valves are used like isolation valves, flow-control valves, and make-up regulator valves.
Collection Basin
It is located at the bottom of the tower and acts as the foundation of the cooling tower for collecting the falling water that has not evaporated or lost due to drift.
Distribution Basin
It consists of holes or nozzles located above the fill. It helps to distribute hot water evenly across the fill material.
Tower Structural Frame
It supports the whole structural materials and transmits all loads to the foundation. It is constructed of concrete and wood. Nowadays, it can be made from fiberglass and stainless steel.
Cooling Tower Applications
It is used in the industrial sectors for removing undesirable heat during the manufacturing processes. It can also be used in commercial and residential buildings, where comfort cooling, refrigerated storage, and equipment preservation are required. It is essential to remove heat from the machinery, equipment, and air conditioning systems because the rising heat among these equipment creates various bad effects in working areas.
This equipment is used for Heating, Ventilation, and Air Conditioning (HVAC) systems in residential and commercial areas. It is used in the food and beverage industry, pharmaceuticals, air and gas generation, etc. for absorbing heat from a closed space and rejecting that heat to the cooling tower.
It is very essential piece of device in power plants to generate power, water is heated to steam by coal, natural gas, or even nuclear radiation. It is used in petrochemical and chemical processing industries to remove heat properly.
Frequently Asked Questions (FAQs)
What is a cooling tower?
It is an important device used to remove process heat from waste water after comes in contact with the air.
What are the types of cooling water?
There are mainly 4 types of cooling towers namely atmospheric towers, natural draft towers, and mechanical draft towers.
What are the functions of a cooling tower?
Cooling tower exchanges heat from the inlet by means of latent heat loss from evaporation during coming in contact with an airstream. A nice heat transfer mechanism is shown by this equipment for having the temperature difference between air and water.
What are the uses of cooling towers?
This equipment is used in nuclear power plants, chemical processing industries, food industries, pharmaceutical industries, textile industries, petrochemical industries, etc. for removing the waste water heat.
