The term cooling tower often conjures up the image of huge cylindrical constructions—hundreds of feet tall—that are often found in nuclear power plants. These are an extreme example of cooling towers, as some cooling systems are much more compact and not really towers at all. In any case, some sort of cooling system is found in most industrial and commercial operations.
The phrase cooling tower is something of a catchall term that may refer to several different types of cooling systems, which vary in method and appearance. Here is a quick primer on cooling towers; the two main types—wet and dry; and the difference between the cross-flow and counter-flow designs.
The Importance of Cooling Towers
Before touching on the different types and configurations of cooling towers, it is important to note the importance of having one. Cooling water streams to lower temperatures is important for almost all industrial, electrical, and chemical applications.
A properly installed cooling tower allows engineers to remove heat and to separate system fluids from pollutants, which may help avoid contamination. Properly functioning and efficient industrial and commercial operations often depend on quality cooling systems.
The purpose of cooling towers is to lower system temperature and dissipate the excess heat into the air, usually through evaporation. Much heat produced in various industrial applications can be classified as “waste heat.” This makes cooling systems an integral component for various commercial industries and applications, whether they are used in chemical plants, power plants, oil refineries, or similar locations.
For appropriate HVAC systems, a cooling tower can be used to separate system fluids from pollutants and contaminants, while also lowering heat.
There are two broad categories of cooling tower: wet and dry. Beyond that, there are several factors involved in determining the specific type and method of a given cooling tower. There are a handful of variables to consider, such as the type of heat transfer, heat transfer medium, water distribution, draft, and location of the draft. Quality of equipment is also extremely important, so make sure your equipment comes from a reputable manufacturer.
Differences between Wet and Dry Systems
Wet cooling towers use evaporation to lower water temperatures. These types of cooling towers are sometimes referred to as evaporative towers. These towers cause a portion of incoming water to be evaporated and released, which cools the remainder of the water stream. Wet cooling towers tend to be a more common heat rejection system than their air-cooled counterparts. This is because they are usually more energy efficient and cost-effective overall.
Dry cooling towers do not use evaporation and, instead, use air cooling to reduce system temperature. Furthermore, there are machines available that combine a cooling system with a plate heat exchanger, such as the one offered by Mahan’s Thermal Products. These hybrid models are usually a more efficient and cost-effective option, so it is definitely an avenue you should explore when designing your HVAC system or determining how to handle process fluids.
Cross-Flow versus Counter-Flow Designs
A big distinction between wet cooling towers is whether they use a cross-flow or counter-flow design. The basic, superficial difference between the two methods is that the cross-flow design directs the airflow in a perpendicular direction to the water flow. The counter-flow directs the airflow in the opposite direction of the water flow. There are advantages and disadvantages to each design.
The cross-flow design uses smaller pumps and generally requires less maintenance. The cost of upkeep is usually less overall, compared to cooling systems that use the counter-flow method. A couple disadvantages include cross-flow designs are more likely to freeze or experience accumulation of dirt and debris.
The counter-flow design tends to make the cooling tower more resistant to freezing, and the heat transfer is often more efficient overall. Conversely, the counter-flow tends to cost more initially and beyond. Operation also tends to be louder and can be noisy, but this is the method to go with if freezing is a real possibility and concern. It is not an uncommon complication, and choosing the appropriate cooling tower can save you hassle in the long run.
Choosing the Right Type of Cooling Tower
The importance of high-quality, reliable cooling towers cannot be overstated. Whether you settle on a wet or dry system, it is important to find one that works best for your particular application, as it will result in significant savings and reliable performance. Keep in mind the advantages and disadvantages of the cross-flow and counter-flow designs. Efficiency is an important criterion in determining the best cooling system, so seek out the best possible performance from the lowest possible horsepower.