Types of cooling towers and how they work
Cooling towers are used to cool the condenser of the chiller. Normally, in a vapor compression air-cooled chiller, the condenser heat is removed through a high-speed fan, but in a water-cooled chiller, the cooling tower generates chilled water, and this chilled water goes to the condenser through an MS pipeline. After heat exchange, the water gets hot and returns to the cooling tower. The cooling tower makes it chilled again and sends it to the condenser. This is how the process goes on.
There are two types of cooling towers:
Cross-flow cooling tower
Counter-flow cooling tower
Cross-flow cooling tower:
From the chiller condenser, hot water enters the cooling tower and is deposited in the water basin. The surface of the water basin is perforated, so water drains to the fill from this area.
In the picture, the yellow thing is called a level floating ball, which is used to monitor the water level of the basin area.
Infill works like the fin of the heat exchanger. The surface of the infill is corrugated, which slows down the speed of the water. Because of this, the water doesn’t fall directly over the cold water collector basin and it gets more time for heat exchange. This is called evaporative cooling. The way you decrease the heat from the tea by blowing on it. Cooling tower chills the water by using the same method. As you can see the water is dropping to the downside and the air is coming from the side. Both of them are crossing each other. That’s why it is called a cross-flow cooling tower.
After this chilled water will collect on the SUMP/cold water collector basin. From here, it will go to the condenser of the chiller. The temperature of the water will become equal to the wet bulb temperature of your area.
Cooling tower is an open-loop system, so when the fan is running, there will be water loss through evaporation. Also water droplets can come out through the airflow of the fan. Drift eliminator reduces this problem. This is a slatted or cellular component; because of this, most of the water drops can’t escape through the airflow. So it falls back into the sump/cold water collector basin.
Advantages of cross-flow cooling tower:
- More power efficient compared to the counter-flow cooling tower.
- Lower maintenance cost.
Disadvantages of cross-flow cooling tower:
- Requires more space to install. So, if you have a space issue, then go for a counter-flow cooling tower.
- Slower than a counter-flow cooling tower.
Counter-flow cooling tower:
In a counter-flow cooling tower, water enters the cooling tower and then sprays through a nozzle over the infill. Because of this process, water becomes too small droplets.
The benefit of this, water surface level increases. When these small droplets slowly go through the infill, water gets proper time for heat exchange. So, the cooling process is faster compared to the cross-flow cooling tower.
Here, water is going downside and air is going to the upper side. Both are countering each other. Because of this, it’s called a counter-flow cooling tower.
The others thing are all same on both type of cooling tower.
Advantages of counter-flow cooling tower:
- This cooling tower needs less space for installation.
Disadvantages of counter-flow cooling tower:
- It consumes more energy. Unlike cross-flow cooling tower, counter-flow cooling tower sprays the water through a nozzle. Because of this extra mechanism, it consumes more electricity.
- Because it has extra mechanical parts for spraying water, the maintenance cost is high.