# Spraybar - Calculating size and quanity of holes



## Jgray152

So I can't seem to find any information on this at all.

Can't really use the common "area of a circle" math because it doesn't really work for diameters of 1" or smaller.

Basically, what size should 15 circles be that would equal a 1" diameter circle.

I couldn't figure it out with equations so I decided to use volume of flow and flow velocity online calculators to figure this out but I don't know if its correct.

I am trying to figure out a proper spray bar configuration for an Fx5 at 600 GPH. 

So according to flow velocity and volume calculators, I would need 15 .258" holes to equal the flow velocity of a 1" hole at 600 GPH. 

What I did was I calculated 600 GPH through a 1" diameter which equals 49 inches per second. 
I then multiplied 49 by 15 which equaled 735 in/s. When I used that number in the calculator to figure a hole at 600 GPH, it came up with .258"

I don't know if this sounds right but I figure if yo uhave 49 in/s velocity through a 1" pipe, then you wan't that same velocity or less through a single hole to reduce in chances of increasing the output pressure. If you only used one small hole at .258", you would have a velocity of .735 in/sec at 600 GPH, problem is, that is VERY VERY VERY high pressure, a pressure we would never ever see so the flow rate would be substaintially lower, probubly around 100 gph if that. Depends on what pressure the Fx5 pump can produce.

So I figure have the same velocity through a small hole would mean you would need multiples of that same size hole, in this case, 15 holes.

Am I going about this wrong?

Then to make things more confusing, to keep equal pressures within the spray bar for a more equal distribution, I would need to have the spray bar tappered from from one end to the other to decrease the ID of the spray bar.


----------



## jones57742

Jgray152 said:


> Am I going about this wrong?
> 
> Then to make things more confusing, to keep equal pressures within the spray bar for a more equal distribution, I would need to have the spray bar tappered from from one end to the other to decrease the ID of the spray bar.


Jg:

Yea kinda!

You are trying to solve this problem in theoretical physics and IMHO it just cannot be solved that way (h... even the big boys with their main frame simulations [ie. numerical methods] cannot get there from from here [although with the input of empirical evidence they can come close, ie. it is probably a cycle of modeling, machining, and experimenting]).

Where I believe that you are "missing the boat here" is the concept of *expansion losses* (I know that you are aware of this concept in a closed hydraulic system with respect to TDH but the concept is also applicable to any hydraulic system, ie. a spray bar).

With the magnitude of the flows exiting from the orifices in a spray bar even a slight geometric anomaly will generate a tremendous flow alteration.


Hence the diameter of commercial spray bars. I have not researched this topic but I believe that the commercial spray bars attempt to maintain flows between 2FPS and 3FPS as these are cleansing velocities (please note that in a hydraulic system flow and velocity are identical) .

TR


----------



## Jgray152

> Yea kinda!


haha, well I kinda figured. lol. 

I know there are way to many factors in play that can increase the output pressure other than a restriction due to the size of the holes. 

Im just trying to figure out, without getting to deep into the science of it, how large the holes should be if I had an X number of holes. 

This seems to be the question on everyones mind when spray bars are being developt as a DIY. 

So I suppose, I will just have to buy some 1" PVC and fittings, drill some holes, starting with the size I figured from my original post, just for the hell of it, and go from there.


----------



## jones57742

Jgray152 said:


> So I suppose, I will just have to buy some 1" PVC and fittings, drill some holes, starting with the size I figured from my original post, just for the hell of it, and go from there.


Jg:

What you are about to run into is the the fabrication tolerances of the orifices by the big boys which I doubt that you can duplicate but I do not know this for certain as you have gotten way further along with some of you other experiments than I ever envisioned. 

TR

Edit: I just reread your post and if you can give me the length of the spray bar, ... never mind! just experiment please


----------



## Jgray152

> What you are about to run into is the the fabrication tolerances of the orifices by the big boys which I doubt that you can duplicate but I do not know this for certain as you have gotten way further along with some of you other experiments than I ever envisioned.


Well I will be making many different models. A few with just a straight piece of 1" PVC with different sized holes and then a few with a tapered 1" PVC pipe. To taper the pipe, I will try to cut out a triangle the whole length of the pipe and heat the pipe up enough to close up the gap that will be made be removing the triangle cutout. This should give me a tapered design. Possibly, it may not work that way.

It will be awhile before I start this but its just another thing to keep my mind going.


----------



## jones57742

Jgray152 said:


> then a few with a tapered 1" PVC pipe. To taper the pipe, I will try to cut out a triangle the whole length of the pipe and heat the pipe up enough to close up the gap that will be made be removing the triangle cutout. This should give me a tapered design. Possibly, it may not work that way.


Jg:

Just my two cents worth but you will be spending a bunch of time on the tapering which is unwarranted.

In order to attempt to explain by exemplification envision a 6' diameter horizontal freshwater (as in the oilfield) tank.

This tank is being filled by a pump in a freshwater pond contiguous to the tank.

The tank has eighteen 1/2" diameter randomly positioned holes .... you get my drift.

TR


----------



## Jgray152

The spray bars I have seen operational have very uneven flow patterns which is why I was going to try an taper the bar. It may not be worth while but it will be interesting to see what the pros or cons are.


----------



## Jgray152

Ok so apprently I was just to tired to comprehend the basic geometry math that needed to be done.

When I was doing the math, it just didn't seem right at all but then another member on the MFK site posted this.



> 1" hole=0.785 square inches(0.5*0.5*3.14)
> 0.785/15=0.052333(area of smaller hole)
> 0.052333/3.14=.016667(radius of smaller hole squared)
> square root .016667=0.1291(radius of smaller hole)
> 0.1291*2=0.2582(diameter of smaller hole)
> comes out the same with the calculator or the basic geometry
> 15 holes 0.258in each.


Then it clicked, he did the same thing I did but it made more sense, maybe because I just have my first food of the day just now. 

Do you see a similarity in the results? It came out EXACTLY the same as what I came up with calculating through fluid velocities, volume and diameters. I never expected that at all.


----------



## Jgray152

I just did some more math using the fluid flow calculations. 

I found this most interesting!!!

No matter what volume of flow or velocity of flow I use for the calculations, I come up with the same diameter for the holes. 0.258". Interesting!


I tried it with 600 GPH, 700GPH and 1000GPH. I then found the fluid velocity for each flow volume and I kept coming up with the same exact answer when figuring for a 1" diameter hose!

Ok Jones, I feel like im on to something! lol


----------

