Lauter Tun Efficiency

by Al Korzonas

I thought that I had covered this before, but since there still seems to be some confusion as to the theory behind the statements, I have, through the magic of ascii graphics, illustrated the theoretical basis for my contention that runoff from a single point is less efficient (in terms of extract) than runoff from multiple points. I have also taken this opportunity to illustrate a third system, used by some, which I also feel is inferior to the lautering system described as SYSTEM #2. All these diagrams are gross exaggerations of the paths of the sparge water and, at the least, the "first runnings" will make their way to the outlet, wherever it may be. Note that the law of physics upon which all three of these theories are based, is:

"The sparge water will tend to take the path of least resistance."

(Actually, it is a phenomenon called "channelling").

SYSTEM #1

Lautering system which draws runoff from a single point: 


       |                                     |
       |                                     |
       |                                     |
       |------------top of grain bed---------|
       |.\                                  /|
       |..\                                /.|
       |...\      \       |         /     /..|
       |....\      \      |        /     /...|
       |.....\      \     |       /     /....|
       |......\      v    |      v     /.....|
       |.......\          |           /......|
       |........\         |          /.......|
       |.........\        v         /........|
       |..........\                /.........|
       |...........\              /..........|
       |............\            /...........|          ....
       |.............\          /............|          ....  <-- these areas
       |..............\        /.............|          ....      represent
       |...............\      /..............|                    "stagnant"
       |................\    /...............|                    sparge
       |.................\  _________________|__V                 water
       |..................\ |                    \
       |..................  |___________________  |
       |_____________________________________|  | |
Once "the sparge water (indicated by arrows) finds the path to the outlet," it will continue to take the shortest path to the outlet, leaving much of the grain barely touched by the sparge water. In addition to the direct path, some channelling would occur along the walls and bottom of the container.

SYSTEM #2

Lautering system in which the runoff is drawn from multiple points from the bottom, such as the "Zapap Lauter Tun" described by Charile Papazian, the "spargebag*-in-a-bucket system" described by Dave Miller, or the "slotted-copper-tube-manifold-in-a-picnic-cooler" (sorry, don't know who introduced this system): 


       |                                   |
       |                                   |
       |                                   |
       |------------top of grain bed-------|     * Note that I specifially
       |                                   |       say "spargebag" as opposed
       |                                   |       to grainbag.  To me the
       |   |      |      |      |      |   |       difference is that the
       |   |      |      |      |      |   |       former has non-porous sides
       |   |      |      |      |      |   |       whereas the latter has
       |   |      |      |      |      |   |       porous sides.  See system
       |   |      |      |      |      |   |       #3, below.
       |   |      |      |      |      |   |
       |   v      v      v      v      v   |
       |                                   |
       |                                   |
       |                                   |        ....
       |\     /\     /\     /\     /\     /|        ....  <-- these areas
       |.\   /..\   /..\   /..\   /..\   /.|        ....      represent
       |..\ /....\ /....\ /....\ /....\ /..|                  "stagnant"
       |--- ------ ------ ------ ------ ---|                  sparge
       |    ^                            __|__V               water
       |    |                                  \
       |    perforated or mesh bottom    _____  |
       |___________________________________|  | |
Since the path of resistance to any of the holes at the bottom is equivalent, the runoff should exit through each of them in approximately equal amounts, thereby roughly equally distributing the sparge water throughout the entire grain bed. Actually, if you've got several hundred holes, the stagnant areas would be so small, that they would be inconsequential to the efficiency. As in system #1, channelling would also occur along the walls of the container.

SYSTEM #3

Lautering system in which the runoff is taken from multiple points on the *sides* and bottom, like the "grainbag-in-a-bucket" system: 


               grainbag (100% mesh bag)
                /
       | | <---'                            | |
       | :                                  : |
       | |                                  | |
       | :----------top of grain bed--------: |
       | |    /  /  /  /  /\  \  \  \  \    | |
       | : <-'  /  /  /  /  \  \  \  \  `-> : |
       | |     /  /  /  /    \  \  \  \     | |
       | : <--'  /  /  /      \  \  \  `--> : |
       | |      /  /  /        \  \  \      | |
       | : <---'  /  /   / \    \  \  `---> : |
       | |       /  /   /   \    \  \       | |
       | : <----'  /   /  .  \    \  `----> : |
       | |        /   /       \    \        | |
       | : <-----'   /   . .   \    `-----> : |
       | |          /           \           | |
       | : <-------'   /  .  \   `--------> : |          ....
       | | .   .   .  /   .   \  .   .   .  | |          ....  <-- these areas
       | :   .   .   v   ...   v   .   .    : |          ....      represent
       | | .   .   .   .......   .   .   .  | |                    areas which
       | :_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ : |                    are touched
       |                                ______|__V                 by less
       |                                          \                sparge water
       |                                _________  |
       |______________________________________|  | |
In this case, the path of least resistance is the "holes" in the mesh bag in the sides, near the top of the bag. In ascii graphics, this was very hard to illustrate, but my intention was to show that more sparge water would tend to exit the bag near the top, less would exit partway down the side of the bag, less and less as we look at points further down the side of the mesh bag.

In summary, it is my contention that system #2 is the most efficient of these three systems and virtually all lautering systems can be approximated by one of these three systems.

Al.
[Read] Read Jack Schmidling's counterpoint that this description does not apply to an EasyMasher system