What is the right mash flow rate?

[clay9_24]

I have read almost everything I can find related to the wort recirculation flow rate and am just as confused as when I started.

What I am specifically trying to find is an equation or ratio that will tell me what water flow rate I need in the mashing process.

Obviously, I am aware of the endless variables that lead up to that point so let me try to generalize if I can.

I am plan on fabricating my own mash tun for my Senior Design Project. I am flexible on all of the dimensions (but have some preferences in mind due to ease of fabrication). I plan on having a full false bottom in my mash tun and heating with a heat exchanger that I am building. Before I can ever get into the design of the heat exchanger I need to try and nail down the flow rate of water through the grain bed.

1. For a cylindrical grain bed what is the speed that water will flow down through it, is the maximum rate to high for proper mashing?

2. Should the space under the false bottom be minimized or maximized to any specific point?

3. Should I build my equipment specifically for one recipe at one volume?

4. It looks like the maximum amount of grain that i will be able to mash is around 100lbs due to boiler volume limitations.

5. I will have mechanical grain bed agitation to prevent large batches from clogging. Should it run constant or intermittently?

6. If someone out there with some experience in hydrology could tell me the permeability factor for a grain bed(dry, wet, disturbed, and settled) I could solve Darcy's equation for the flow rate. (what I would give if my hydrologist roomate hadn't just decided to get a job and leave)

I'll try and stop my questions here. One could almost write their dissertation over what I just asked. Any input would be greatly appreciated! I would even snail mail you a beer if you solve my problem!


Clay

 

[z987k]

These are all questions I'd love to know the answer to, but I don't know if we really know. I really don't think I've ever read anything on here discussing the topic.

Hopefully someone will come along, but in the meantime, have you searched the library at the Journal of the Institute of Brewing? Might want to try posting the same thing over at probrewer. Another possibility is to contact Siebel and see if they want to help out.

Maybe someone who has done a recirculating design would know as well. Might try a search on here for RIMS and HERMS.

 

[EMPyre]

Um, maybe you should take an hands on approach, go get some empirical data, it would certainly lend more cediblity to your design criteria than justifying by say 'that's what some dude on teh webz' said. I worked my ass off for a failed senior project, but I learned a lot and had a lot of fun in the process. Just sayin'

 

[CodeRage]

I am not a mechanical engineer by any means. So this is me speculating. I think that the higher flow velocities would increase the vectoring of the mash straight to the pickup tube of the false bottom. This would leave dead spots around the bottom of the MLT.

 

[EMPyre]

I'm pretty sure I read somewhere that John Palmer had done some serious research into grain bed flow with respect to manifold/FB design. That data could be helpful... Otherwise do you think it a fair assumption to model the flow rate based on say .125" ID rough surface tubes creating a total cross sectional area for the overall MLT ID?

The sad thing here is unless you have some conections with access to some serious modeling software you're not likely to get a good value. I'd shoot for approximations based on test data. Its what you're likely to see anyway when you get out there to put that degree to use...

 

[The Pol]

There is no real answer here.

What is the lautering device like? Button Falsie? Small Hole Falsie? Large Hole Falsie? Manifold? Braid?

What is the grist like? A lot of husk material? Little husk a material (wheat)?

What is the crush like? Coarse? Medium? Fine?

Each brewery will have a limit to how fast the mash will run... but it will vary on the system, grist and crush etc.

 

[ScubaSteve]

I think you should go on a few brewery tours, and ask that same question. It'll be fun, and who knows....you may make some nice connections for a hookup on yeast, etc.!

The big boys do it a lot differently than we do, due to the physics of 1,000 lbs of grain, etc. I'd say on a small scale, the recirc rate is the max you can go without a stuck mash or obvious funnelling/channeling/depressions in the mash. Agitation might affect your clarity into the BK, but YMMV.

 

[jkarp]

Based on a year's experience with my CB-20, I can say it's variable. Some mashes will tolerate a higher flow rate than others. More flow isn't necessarily better however as it can lead to high temperature variations in the mash tun. My suggestion is, if you've done (or seen) a fly sparge, shoot for a similar flow rate.