Cooling towers are categorized on the basis of air and water flow as counterflow cooling towers and crossflow cooling towers. In this article we are mostly focussing on the counterflow type of cooling towers.
Counterflow cooling towers have an induced draught fan at the top section of the cooling tower and it is directly mounted on to the motor. The fan aids in inducing ambient air into the tower which creates an upward draft. The speed of the exhaust air is more than the speed of the air that is entering. This helps in creating a low pressure drop and having a lower circulation.
This design is very desirable for industrial applications where cold water temperatures are of high importance. The mechanism that comes into play here is the “counterflow mechanism”. The direction of airflow is opposite to the direction of water flow. The airflow goes up vertically after it enters the open area below the fill media. Spray nozzles and sprinklers are used to spray water near the top of the tower. It then flows downward through the fill, opposite to the direction of airflow.
In a counterflow cooling tower, the following is the flow of air and water:
- Flow of air is vertical through the fillings at the top portion
- Flow of water is downward
An induced draught fan is used in a counter flow cooling tower. The air is drafted upwards with the help of the fan which is attached to the motor. This helps in faster pulling in and exhausting the air, moreover results in lower pressure and circulation.
To help you get a clear understanding of the design and working of the counterflow cooling towers we let us dive into the cooling towers that actual industries are using. What’s better than learning from practical examples? So let us take a look at our series of counterflow cooling towers that are already being used for various industrial applications.
DFC 60 Cooling Tower Series:
Delta’s DFC-60 series is a square or rectangular shaped Induced Draft Counter Flow Cooling Towers, which are often called Cuboid Shaped Cooling Towers. The shape & design of the cooling towers ensures even water distribution and efficient dissipation of heat. The structure of these cooling towers is modular and highly resistant to temperature and weathering. Suitable for all industrial applications, these rectangular shape cooling towers can be camouflaged in the architectural design of the place of installation.
Heated water enters the cooling tower through the hot water inlet passing through perforated branch pipes spreading the water evenly through the splash caps on heat exchange fills. As the water flows downwards it loses heat to the upward moving ambient air in the counter flow direction. The upward moving air passes through a high-efficiency drift eliminator, which captures water droplets and mist in the air, which is retained back in the cooling tower. Thus reducing the water losses considerably. The adjustable pitch Axial Flow Fan is directly mounted on the high-efficiency motors, specially designed for cooling tower application.
DFC 50 Cooling Tower Series:
Delta’s DFC-50 series is a circular Induced Draft Counter Flow Cooling Towers, which are often called round bottle-shaped cooling towers. The shape of the cooling tower minimizes the restrictions on positioning & placement of the cooling tower at customer premises, because of the 360-degree air intake area. Assembly and installation of these lightweight and compact cooling towers are relatively easy in comparison to other designs. These cooling towers demonstrate very high versatility, efficiency, and quality. Heated water from your application is pumped through hot water inlets into the cooling tower.
The water is moved upward vertically and distributed over the fills through the self-rotating mechanical water sprinkler. High efficient weatherproof motor, manufactured especially for cooling tower application, is installed at the top of the cooling tower, which is mounted with an induced draft fan. The Axial Flow Fan draws the air from surroundings, which while moving upward through the fills dissipates heat from the water moving in the opposite direction. Hence, Reducing the temperature of the water. Thus, evaporation of water leads to a reduction of water temperature.
Advantages of counterflow cooling towers:
- Distribution of water by spray method makes the cooling tower have better efficiency.
- Heat transfer is more effective since the water is broken down into smaller or fine droplets due to spraying.
- Maximum performance is obtained since, in this type of cooling tower, the coldest water comes in contact with the driest air in the basin at the bottom of the cooling tower.
- Low possibility of algae growth due to the enclosed structure of these cooling towers. The inner parts and water do not come in direct contact with sunlight, so it is more resistant to such biological intrusions.
- Lower maintenance expenses as biological growth are less and need to be treated less often.
- The water and air interaction lead to a partial leveling of temperature and also water evaporation.
- The air with water vapor is eliminated from the top section of the cooling tower
- Both types of cooling towers use a collection basin to cool water.
Working of the counter-flow cooling tower:
- A single fan is present at the top of the cooling tower.
- There is a rotating water pipe distributor fitted right below the fan.
- Water is transferred by the pipes of the water distributor only from one side.
- This water pressure generated due to the transfer of water from one side results in the rotation of the distributor
- This helps in even distribution of water over the inlet louvers
- The water-dropping due to gravity meets head-on with the upward moving air current that is sucked in by the fan.
- The water is thus cooled by air.
- The water gets collected at the bottom of the cooling tower. The cycle then continues.
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