A cooling tower is used to remove heat from a facility or a building. Spraying water helps to dissipate the heat and bring the temperature of the building down. Air enters from the sides of a tower, and it flows past the falling water. This air thus helps in the transfer of heat to the water.
All this results in the evaporation of some amount of water. This evaporated water flows out as mist. As this water evaporates, we can experience a cooling effect through the tower. Hence, the essential purpose of a cooling tower is being processed in this manner.
Use of a cooling tower
A cooling tower serves the purpose of ventilation, air conditioning, and heating. It is an energy-efficient and cost-effective method used for cooling down a system. It works as an air conditioner in large offices and schools. Many industrial setups install a cooling tower for easy heat dissipation from any property. In the below-mentioned places, you can find cooling towers:
- Petroleum refineries
- Food processing plants
- Natural gas processing plants
- Petrochemical plants
- Other chemical industries
Fundamentals of a cooling tower
We can understand the concept of cooling towers by taking the example of ‘wet bulb’ temperature. Imagine a hot summer day with a 45 °C temperature. The relative humidity of the atmosphere is around 40%. A standard room thermometer will give a reading of 45 °C because it is the dry-bulb temperature.
Now take another thermometer and attach a wet cloth to its dry bulb. Rapidly swirl both the thermometers through the air. This device is a swing psychrometer. After some time, when you notice the reading in both the thermometers, you will realize that the dry bulb one is still steady at 45 °C. But you will see that the reading in the wet-bulb thermometer has dropped down to 30 °C.
This drop in the temperature is due to evaporative cooling. Hence, when water is spread over a surface, it comes in contact with air. Therefore, it evaporates and rises in the atmosphere as a drop. It thus produces a cooling effect on the surface where it is initially present. A cooling tower works on the same principle.
One can also understand the basic principle of a cooling tower by a simple everyday example, i.e., sweating. As the temperature of our surroundings rises, our body starts releasing water in the form of sweat. The evaporation of this water occurs, thus leading to a cooling effect.
Apart from a system that sprays water into a cooling tower, we may also need other requisites. These will ensure the proper functioning of a cooling tower. These include:
- Fans that replace the already existing moisture-containing air
- A heat source that provides a constant heat supply to the runoff.
- We may also need devices that ensure continuous water circulation through the system.
Factors that determine the working of cooling tower
While selecting a cooling tower, there are a few factors that you may need to keep in mind. These are:
- The temperature of the water inlet.
- The temperature of the water outlet.
- Water flow rate
- The temperature of the wet-bulb thermometer.
Understanding the concept behind a wet-bulb thermometer is essential. It will show different readings concerning a dry bulb thermometer in most cases. The exception arises when the surrounding air has higher water content. In this case, both the bulbs will show similar readings because, at that time, the environment has 100% relative humidity. The surrounding air thus becomes incapable of accepting more water. Therefore, the lower the reading wet-bulb shows, the more a cooling tower is capable of rejecting heat.
Spreading water over a surface exposes it to the air. This causes the water to evaporate and produce a drop in temperature. Hence, this wet bulb reading plays a crucial role in determining the size of the cooling tower.
Time taken by the cooling tower to transfer heat
A cooling tower cannot control the rate of heat transfer. All it does is transfer the heat it receives. The rate of heat transfer and the rate of evaporation is similar for a cooling tower. Both these rates remain unaffected by the size of the cooling tower.
The flow rate, the size of the cooling tower, and the wet-bulb temperature all play a crucial role in determining the time taken by a cooling tower for heat dissipation. However, the cooling tower cannot control the inlet and outlet temperature. Hence, you can alter these two factors, which can enhance the performance of a cooling tower.
Conclusion
So, this was all about cooling tower heat transfer fundamentals. Now, you will find it pretty easy to purchase the right cooling tower for your place. If you are looking for more assistance, you can even get in touch with a team of experts at Towertech to get the right cooling tower installed in your factory.
