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Identity.Ales
08-12-2016, 02:50 PM
I'm trying to size a new whirlpool pump for a 50 bbl. system. I've been combing through text books without finding much definitive information. So far I see that Kunze recommends a inflow velocity of less then 3.5 m/s and "as high a mass flow of wort as possible" for a flow rate. Otherwise I've seen velocity rates up to 5 m/s (Handbook of Brewing) and down 2.1 m/s (MBAA).

I'm not much of an engineer but it looks like whirlpool success is governed by velocity, tank dimensions (friction on outer wall), and design tweaks.

Omitting design tweaks does anyone have experience or information about picking the correct velocity for a whirlpool with a D/H ratio of 2:1?

Thanks
Kyle Larsen
Siren Craft Brew

dick murton
08-28-2016, 10:48 AM
Beg, Steal, Borrow, or even buy a copy of the EBC Manual of Good Practice: Wort boiling. This had a section written by Prof Victor Denk of Weihenstephan, probably the world expert on whirlpools. The speed of ca. 3.5 m/s has shown to be the best wort speed due to low shear stresses which could destroy the trub.

It is not just the speed of entry into a whirlpool though - the volume is critical. So you need to be able to cast between 10 and 20 minutes - 10 minutes is generally (but not by all of course) considered better than 20 minutes. The most important thing is to be able to clean the pipes at adequate flow rates.

For what it is worth, the two major breweries I have worked at have taken 15 - 20 minutes to cast, which because of variable brew volumes at one of them, equates to about 3.5 metres / second.

From one of my old companies best practice documents The inlet speed should ideally be at 3.5 ms-1 but never greater than 5 ms-1 to prevent shearing of the wort and trub particles. At flow rates greater than 5 ms-1 torus eddies can form which will disrupt the cone.

Kunze - inlet speed between 1.5 - 4.5 m/s ( the smaller the whirlpool the higher the speed)

Comment by another brewer on one of our WPs that we were having problems with (which merely confirmed our understanding)

Inlet velocity:
Determines the initial rotation speed. Large whirlpool operate at a lower inlet speed that small whirlpools. Recommended velocities are 1.5 to 3.0 m/s. A higher inlet velocity gives more shear forces and oxygen pick-up at start of whirling and does not give a better rotation and a longer rest time.
For large whirlpools a high inlet velocity may lead to too long rest time before the rotation stops.

Inlet system:
A well developed flow pattern at the whirlpool inlet is important to prevent turbulence and vortices. Minimal 1.5 m straight pipe of constant diameter is recommended before the inlet.


Why don't you purchase a pump which will allow you to cast in say 10 - 12 minutes, with a flow of up to 4 metres / second, fit a VSD to it, so you can vary the pump speed a little to get the best results. You may need to vary it form brew to brew depending on the hop loading.

Also note that you can simply overload the WP with hops, and never form a decent trub cone. Conversely, when I used extract only for one particular beer, I had to replace some of the extract with pellets to give a good cone.