nozzle location on air cooler header

[srfish]

Years ago I was taught that if the width of an air cooler header was over 8 feet, more than 1 pair of nozzles should be used. Exceeding this width limit meant that there would be too much maldistribution. Now I am seeing more and more air cooler headers that exceed the 8 foot limit. There is one recent case where the header was over 13 feet in width and there was only 1 inlet and 1 outlet nozzle. What would be a good maximum width for a single pair of nozzles?

 

[speco]

srfish,

I would agree that the arrangement you have described looks a little suspicious. The API-661 requirement is that the lateral velocity in the header should not exceed the tube velocity for the following pass (or words to that effect).

I would suggest investigating further, however. Two obvious questions come to mind. First, what is the velocity through the nozzle (especially at the inlet)? The second question is the internal pass arrangement in the tube bundle. It may be reasonable to have one nozzle in a wide header if the number of passes per row is more than one. That is, say a twelve-pass, four-row bundle, for example. However, this type of arrangement doesn't come up very often.

I would tend to go to more nozzles if the header is more than about 6 feet. However, sometimes the customer is trying to simplify their piping, and that forces the cooler manufacturer to use fewer nozzles.

Regards,

Speco (

http://www.stoneprocess.com)