Due to its extensive communication network with China, Metanoia has a sales representative from Seagull cooling tower manufacturer. These companies are one of the largest cooling tower manufacturers in this field, which claims to compete with European manufacturers with similar quality but lower prices. Below you can see the catalogs and resume of this company.
The company’s catalog completed projects production stages
Types of cooling towers are divided according to the flow path of water and air, construction method and heat transfer method. Cooling towers have different forms; Sometimes their shape is round, cubic or hyperbolic, and sometimes the butterfly is placed on the side or on the top, or there is no butterfly at all. There may be differences in the distribution of water inside the device, which can be circular, nozzle spray, or gravity.
In this article, we are going to categorize the types of cooling towers and while introducing each one, we will also explain their advantages and disadvantages. In the following, we will examine these towers in terms of water circuit and introduce its forms.
The low economic costs of using cooling towers, along with the increase in production efficiency, is the most important reason for the high consumption of cooling towers in the industry. Many industrial and semi-industrial factories that use light and heavy machinery have made use of this equipment to increase their efficiency.
In fact, the use of a cooling tower in the industry is considered an inseparable principle of any industry. Various industries such as steel, plastic parts manufacturing, non-ferrous metal forming industries, clothing production, casting industries, wood, oil, petrochemical and power plants are the biggest consumers of cooling towers. In a general description of the cooling tower, this device is used in two main applications.
How the cooling tower works
The way the cooling tower works is that inside the cooling tower, air that has some moisture with it comes in contact with hot water. In this case, due to the energy difference and the concentration gradient, energy and mass are transferred from water to air.
In the continuation of the work, water also evaporates from the liquid phase and turns into a vapor phase. In this case, due to evaporation, it also takes some energy to the gas phase; It should be mentioned that the amount of this energy is very high, which is the reason for the high latent heat of water.
In this way, due to the evaporation of some water and the removal of heat from the liquid phase, the temperature of the water decreases. The condition for carrying out this process is that the air used in the tower is accompanied by a small
amount of moisture to have the capacity to accept evaporated water.
Types of cooling towers in terms of air flow
Cooling towers are classified into the following in terms of air flow.
- Natural flow
- Mechanical flow
- Forced flow
- Inductive current
- Compound flow
This category of heat absorption exchangers has different types, each of which is designed according to specific climatic conditions and different applications. But in general, the task of cooling towers is to absorb excess heat of liquid fluids, which is possible with fresh air. In other words, the cooling tower is a device that receives the heat generated in the processes, machines and industrial devices from the flowing water and transfers it to the atmosphere through evaporation and returns the cool water to the system.
Natural flow cooling tower
The natural or atmospheric flow cooling tower has no impeller and does not use any parts to make the air flow. In this type of tower, the water inside is only sprayed and the air flows naturally. These towers are very cheap and do not perform reliably and are highly affected by wind and weather conditions. In the figure, you can see a simple atmospheric cooling tower, where water is distributed through nozzles and at the same time, air also flows naturally inside the tower.
Natural flow cooling tower components
- Concrete and steel structure
- packing
- Drip catcher
- Water distribution system
- Water pond
Hyperbolic cooling tower
A hyperbolic cooling tower is a type of natural flow that is made of concrete and has very high dimensions and height, and is usually used in power plants and factories that need a lot of cool water.
The air flow in these towers is caused by the pressure difference in the height. The construction of this type of cooling tower is very expensive, but it has a very reliable performance and is used for sensitive industries.
Advantages of natural flow cooling tower
- Low energy consumption (no electricity and energy consumption)
- Suitable for the environment
- Very low noise
- Reliable and safe operation
- No air recirculation possible
- Occupying limited space
- Limited maintenance and repairs
- Very long life
Mechanical flow cooling tower
A mechanical flow cooling tower uses one or more propellers to circulate the air. This type of cooling device has stable performance and is less affected by wind and environmental conditions.
In this type of cooling tower, a fan is used as a driver to create air flow. As you can see in the figure above, the air enters from both sides of the device by means of a fan and exits upwards.
Advantages of mechanical flow cooling tower
- Very small structure
- Small space occupation
- High efficiency and performance
- Stability to weather conditions
Mechanical cooling tower components
- Electro-Motor
- the butterfly
- Drip catcher
- packing
- Water distribution system
- Structure
- Water pond
Forced flow cooling tower
Forced flow cooling tower is a type of mechanical flow in which the propeller or propellers are located in the air inlet. The speed of air entry is high, but the speed of air exit is low, which causes weakness in preventing air recirculation.
This type of cooling tower is economical in terms of construction and is suitable for most industries. This type of cooling tower in small sizes is usually made of metal and in large sizes it is made of concrete.
The large forced flow cooling tower used in industries is designed and built based on user requirements.
The impeller of this type of cooling tower is usually of centrifugal type. These towers have a high static pressure, but they have a high power consumption and a lot of noise. The impeller of this tower is subject to freezing due to its position in the air inlet path in the environment with cold weather.
Induction current cooling tower
The induction flow cooling tower is a mechanical flow type. In this cooling tower, the propeller or propellers are placed in the air outlet and the speed of the air exiting the fan area is higher than the air entering the inlet area.
Due to the location of the propeller in the hot air outlet, it is not possible for the propeller to freeze in cold seasons. Also, in this type of tower, air recirculation does not occur by itself. Many of the small cooling tower models are of the induction type, which are capable of reducing the temperature of a certain amount of water flow in a small size with the help of a propeller.
In this type of tower, due to the shape and mechanism of operation, it is not possible to recirculate the air. This model of towers is made from small flow rates of 15 gallons per minute to 700,000 gallons per minute and more, and it is a proof of the increasing use of this cooling tower model.
Mixed flow cooling tower
The flow cooling tower is composed of different types of cooling tower that looks like a natural flow cooling tower, but its height is usually lower and one or more propellers are used inside it to make the air flow. Also, in this type of tower, in cold seasons, the propellers may be off, and if needed and under heavy load, the propellers of the system will start working.
Usually, the design of the mixed flow cooling tower is such that the fans are forced to work only during peak load or extreme heat. Mostly, the fans are placed in the air intake area and they blow the fan into the cooling tower like a forced flow, and the air exits from the top of the cooling tower.
The construction and use of the mixed flow cooling tower results in significant savings in energy consumption. During use, the fans can be rotated at low speed first, and if needed, increase the speed of the propellers to increase the cooling rate.
Hybrid cooling tower
Hybrid cooling tower is another type of cooling tower that is a combination of two dry cooling towers and wet cooling towers. In this cooling tower, first the water with a very high temperature enters the coil and is cooled by the air flowing in the tower, and then the water is sprayed on the heat transfer surfaces and cooled like a normal cooling tower.
Division of cooling tower based on the path of air flow
There are other types of cooling towers based on the flow path of air and water relative to each other inside the cooling tower. This division is as follows.
- Counterflow cooling tower
- Cross flow cooling tower
Counterflow cooling tower
The cooling tower is opposite to the flow of water in the direction opposite to the direction of air flow. Usually the flow of water is from top to bottom and the direction of air flow is from bottom to top. You can see the opposite flow in the figure of the cooling tower. The water distribution system in the counter flow cooling tower is usually done by pump pressure and nozzle.
The nozzle distributes the water as much as possible on the surface and in the form of drops. The heat transfer surfaces used in this type of cooling tower should be in a form that allows air to enter from the bottom. The propeller is usually placed in the central part and in the upper part and sucks the air from the bottom to the top.
Usually, due to the mechanism of operation and the path opposite to the direction of the weather, water ejection is high in this type of cooling towers; For this reason, drip catchers are often used in the upper part of the water distribution system. The drip catcher allows air to pass through, but captures water droplets and returns them to the system
Cross flow cooling tower
In the cross-flow cooling tower, the water flow path and the air flow path are intersected. Usually, the water flow is from top to bottom and the air flow is horizontal. In the figure below, you can see the cross flow cooling tower.
This type of cooling tower has a high water drop height. Therefore, the water easily gets a chance to come into contact with the air, evaporate and cool down more. Due to the intersecting path of air and water flow, the possibility of throwing water drops from the cooling tower has been reduced to a minimum, and as a result, water splashing in this tower model is very small. The way water falls in these cooling towers is done by gravity. Therefore, the water distribution system is simpler and has a longer life.
Division of cooling tower based on water circuit
There is another type of division based on water flow circuit for cooling towers. Based on this, cooling towers are divided into the following two categories.
- Open circuit
- closed circuit
Open circuit cooling tower
The open circuit cooling tower is called the same as the normal cooling tower, in which the water comes out of the pipe when it enters the cooling tower and is sprayed inside the device, and it is in contact with the air, and the so-called open circuit, and all the way, water It is not inside the tube.
Closed circuit cooling tower
Inside the closed circuit cooling tower, coils are used and the system water passes through these coils and cools. The only difference in the operation of a closed circuit cooling tower compared to the operation of a conventional cooling tower (open circuit) is to prevent evaporation and precipitation in the system water; In such a way that the water of the system is not in contact with the air due to passing through the coil, so the water does not evaporate and impurities do not enter it. But in the closed circuit cooling tower, at the same time, water is poured on the coils in another circuit, and this water evaporates from the surface of the coils in the vicinity of the air flow created by the fan and finally cools the coils. .