Manifold Design Question

So I've read what Palmer has to say on manifold design, but I have another question about it that wasn't addressed in the book.

How does the number of openings in the manifold, and the spacing or density of the openings from the outlet effect flow through the grain bed?

It was suggested me that with a manifold with an even spacing of slits, or holes, will mostly draw the liquid from closest to the flow outlet. They suggested that I put more openings further away from the outlet than I do closer to the outlet to compensate for this.

We're trying to achieve even rinsing of the grain bed for constant RIMS re-circulation. Is a standard manifold design not ideal for even rinsing?

Here is a quick drawing I did to illustrate what I'm talking about:

Intuitively, your overengineered drawing makes sense and I suspect with plain water it would achieve at pulling liquid more evenly from across the bottom of the vessel. BUT, I wonder what kind of dynamics are created when using grain such that the slits become somewhat "plugged" by grain causing a restricted flow. It would seem the grain restriction on the slits would be the most at the nearest slits and least at the furthest slits from the output tube, perhaps to a point that it equalizes the draw of liquid into the manifold when using the underengineered drawing. I'm basically just thinking out loud here.

Interesting thought. But when we're taking so many steps to avoid grain bed compaction with rice hulls and pressure gauges or grants, or what ever, then that would start to negate a natural flow equalization wouldn't it?

Has anyone, or have you heard of anyone, making their manifolds in a manner like I'v shown above?

An interesting idea. No, I haven't seen this before on here. I have no idea how you'd actually be able to tell if it's making a real difference, other than perhaps an increased mash efficiency number. Take one for the team and build two out of CPVC. Make one the usual way and one with your staggered slits or holes and see if it makes a difference. You could use the same fittings for both manifolds, so the cost would be less than a dollar or two just for the tubing. FOR SCIENCE!

thekraken said:

Interesting thought. But when we're taking so many steps to avoid grain bed compaction with rice hulls and pressure gauges or grants, or what ever, then that would start to negate a natural flow equalization wouldn't it?

Click to expand...

It very well may. It would be interesting to test it somehow, and as Lando mentioned it could be fairly inexpensive to test using CPVC or even PEX for that matter.

I would think you could create a rudimentary experiment using some kind of makeshift baffle to segregate the MLT into two parts. Using some colored liquid (food dye; blue and yellow) put the solutions into each half and begin the draining. Depending on the output green color you should have a general idea of the mixing ratio. If you are able to keep the two halves sealed off from each other then you may even see one side drain before the other. Something like playdough or poster putty could help create a good temporary seal. Again just thinking out loud.

thekraken said:

Has anyone, or have you heard of anyone, making their manifolds in a manner like I'v shown above?

Click to expand...

I had the idea of ever-shrinking distances between furthest slits when I was building my yet-to-be-used copper manifold but since I had no ground for basis, and was using a relatively expensive material I opted to stick with evenly spaced and frequent distances. I did however avoid putting in any slits within the closest 1.5" (3" overall span) on either side of the horizontal section opposite the output tube to discourage a central sucking point.