HLT Stirrer?

An "HLT" is a "Hot Liquor Tun", which supplies your hot water for mashing and sparging, right?

I have seen several threads about "HLT Stirrers". Why would you need to stir a tank of hot water?

I can see a stirrer for a MLT, to mix the grain and water.

Am I just confused on the the terminology?

I've wondered the same but I 'think' its for when people have a thermostat controlled heat source and they use the stirrer to make sure all the water is the same temp.

The stirrer keeps the whole tank at the same temp, instead of having a hot spot right near the element.

OK, that makes sense.

Thanks.

(one more thing to think about...)

Stirrers are generally seen in the HLT when the HLT is used for a HERMS. You will have a heat source, and you will have a coil for the HERMS that will extract heat. Since you have these two opposing forces, a stirrer is required so that your water is homogenous in temperature. Otherwise the HERMS coil will create a cold spot around itself from extracing heat, the element will create a hot spot, and your thermowell will have no idea what the TRUE temp is inside the HLT.

In a standard HLT, a stirrer is not required.

If you have a propeller to slowly stir the HLT which direction should it rotate.
Pulling the water from the bottom up or pushing the top water down and why one way is better than the other?

Pushing up or down does not matter. One can use a flat paddle and it will cause enough circulation to make the temps homogenous. The problem is not stratification (layering) it is the problem of heat being applied and removed from different places in the HLT. Any stirrer that can break the surface tension of the water will suffice.