Importance For The Cooling Tower Nozzle

Cooling tower nozzle is tasked with getting the hot water that you want to cool delivered to the cooling tower fill, the cooling tower nozzle also play the very important role  in the duty of a cooling tower. Cooling tower nozzle is involved in the following aspects of a cooling tower's performance evaluation.

Water Distribution

Of course, the most obvious impact of cooling tower nozzle is due to its primary job of getting the hot water to the cooling tower fill. Ideally, cooling tower nozzles are located and sized so that they provide a uniform pattern of water over cooling tower fill with no gaps between their spray areas. You’ve spent a "few dollars" to put cooling tower fill into your cooling tower, so now you need to make sure that you utilize it to its fullest extent by making sure that it is totally wetted out and all sections of cooling tower fill receive a constant amount of water. All published performance data for cooling tower fill is based upon this assumption.

Gaps in spray coverage can lead to air bypass because dry cooling tower fill offers lower resistance to airflow, and air will always take the path of least resistance. This will result in airflow being stolen from wet cooling tower fill sections where it is needed to cool the hot water. Also, since air and water are both fluids, the gaps are not 100% constant in their location. As the competing fluids interact with each other they tend to pulse and shift around. This causes some of the cooling tower fill to experience alternating cycles of wet and dry times which will promote scale formation within the cooling tower fill. As scale builds up in a fill it starts to adversely affect its thermal performance capability, and in the extreme, can totally block airflow from the fill and potentially cause structural damage to the cooling tower if the cooling tower fill's weight gain from the scale is excessive.

Spray Zone

Another way that the spray system affects a cooling tower’s thermal performance is from the cooling that happens as soon as the water exits the cooling tower nozzle and falls to cooling tower fill. The cooling effect in this spray zone can vary from 5-15% of the total cooling provided by the tower. The key to cooling here is to maximize the interaction between the hottest water and the coldest air. Thus, a nozzle that generates very small droplets will have a greater cooling effect than a nozzle that makes big, fat droplets. This is similar to the cooling effect of walking through a fine mist on a hot summer day as opposed to being hosed down by a fire hose.

Drift Eliminators

With ever-increasing scrutiny being paid to drift emissions from cooling towers, you have to be aware of the role that cooling tower nozzles can play on drift. Unfortunately, the fine spray of very small droplets that is beneficial from a cooling perspective creates a much more difficult challenge in preventing those same very small droplets from exiting the cooling tower as drift. This can be made even worse if the circulating water has very low surface tension due to water treatment that includes surfactants or due to compromised make-up water sources from wastewater treatment plants.

As the surface tension of the water decreases, it causes smaller and smaller droplets to be formed. When you combine this with a pressurized water distribution system, especially if you are overpumping it and have a higher than expected pressure at cooling tower nozzles, you can actually generate a mist.