Cooling Towers: Choosing Between Counterflow and Crossflow

Choosing which cooling tower is best for your project can be intimidating. There are so many aspects to consider, such as size, material, and configuration. Of those three, the first two are pretty self-explanatory. When talking about configurations, however, understanding the differences is the first step in choosing the tower that best works for your HVAC system. The main difference between the two configurations is how air flows throughout and ultimately cools the water during its journey.

 

Crossflow Cooling Towers

 

As hot water enters a crossflow cooling tower, it flows downwards solely due to gravity. Spray nozzles in the tower rely on this gravity rather than external pressurization to distribute the water throughout the fill. As water flows downward, the air is blown horizontally across the water, thus cooling it as it falls. This “cross” between water and air is what gives this configuration its name.

 

Counterflow Cooling Towers

 

Rather than relying on gravity to distribute the water throughout the cooling tower – in a counterflow design, that water is distributed downwards throughout the fill via low-pressure nozzles. Airflow in this configuration travels vertically, directly against the flow of water.  There is generally a fan above the nozzles which pulls the air upwards.  Once the water has been cooled, it then drains down to a cold water basin location at the bottom of the tower.

 

Which Configuration is Best?

 

So, why would you choose one configuration over the other? It’s going to depend on a variety of factors – the biggest being available space. Counterflow towers tend to require less area on the ground. For buildings with limited floor space (or rooftop space), this option may work best. These towers tend to be taller, so keeping that in mind when thinking about any height restrictions of the space is advised. Crossflow towers are also lighter in weight compared to crossflow towers. So, for areas that have operating weight restrictions, this may be the best option.

 

Other than the size variable, efficiency and serviceability also play key roles when deciding on a cooling tower configuration. Crossflow towers generally offer more efficiency and are easily maintained over time, thus giving them extra appeal for projects where the space issue isn’t a concern. What makes them more easily serviced is that crossflow towers often have a built-in (or option to do so) service platform. From that platform, workers can access the hot water basin to perform preventive maintenance measures or assess any issues. In fact, even when in operation, workers can inspect certain components – including drift eliminators. In counterflow towers, access to the nozzles is more difficult (impossible while operating). Thus, any maintenance that needs to be done relies on shutting down the tower for some time. This can halt operations or productivity in certain situations.

 

Also, because crossflow towers don’t utilize pressurization for water distribution, operating costs tend to be less. Energy is saved by not relying on pressurized nozzles to distribute the water.

 

Environmental considerations should be considered as well when choosing a configuration. For those in areas where noise is a concern, crossflow towers are likely the better choice. The distance between the bottom of the fill and the cold water basin in these towers is pretty small. So, not a lot of noise is generated by falling water droplets. In crossflow towers, on the other hand, water droplets fall into the basin from a much higher distance. This generates more noise – especially in larger towers. There are methods you can take to reduce this noise, such as utilizing sound attenuators.

 

Climate plays a role as well. One thing you want to avoid is water freezing inside the fill of a cooling tower. In areas that see a lot of cold weather, this is more easily done with a crossflow tower. The reasoning behind this is that water distribution in crossflow towers leads to much less channeling of water inside the fill that could turn to ice when temperatures fall below freezing.

 

In hot climates, counterflow towers may be a better option to avoid algae growth inside the tower. Crossflow towers leave a part of the plenum directly exposed to sunlight. The heat this generates stimulates algae growth, which must be carefully monitored and regularly treated.

 

Cooling Tower Experts – You Don’t Need to Choose Alone

 

Fully understanding enough about each type of cooling tower in order to make an informed decision on the best option is difficult. Luckily, the folks at Cooling Tower Experts know these decisions can be daunting. Our goal is to help make the process easier. Our experts bring years of industry knowledge and field experience, working with cooling towers and HVAC systems across multiple industries. We have truly become experts and want to share that knowledge with our customers. Our services range from project consultation to training to service and maintenance. Depending on how much or little help you need, we’ve got an option for you. The biggest things you need to worry about when replacing an existing tower or installing a new one are choosing the best option and then having a service/maintenance plan in place to keep that tower running efficiently for years. We’d be happy to get you on the right track – contact us to start your project today!