Why Are Nozzles Important?
Everyone knows how important the fill is to a cooling tower’s performance. Since fill is the heat transfer medium around which the “box” that is the cooling tower is built, you could argue that it’s the most important factor in determining just how well your cooling tower performs. However, since the nozzles are tasked with getting the hot water that you want to cool delivered to the fill, the nozzles also play a very important part in the duty of a tower. Nozzles are involved in the following aspects of a cooling tower’s performance evaluation.
Of course, the most obvious impact of a nozzle is due to its primary job of getting the hot water to the fill. Ideally, the nozzles are located and sized so that they provide a uniform pattern of water over the fill with no gaps between their spray areas. You’ve spent a “few dollars” to put 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 fill receive a constant amount of water. All published performance data for a fill is based upon this assumption.
Gaps in spray coverage can lead to air bypass because dry 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 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 fill to experience alternating cycles of wet and dry times which will promote scale formation within the 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 fill’s weight gain from the scale is excessive.
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