Dedicated Herms Guide, Problems And Solution Thread

[idzy]

In my experience the biggest restriction when it comes to flow is creating a vacuum and compressing your grain bed. You cannot infinitely turn up your flow. Best way is as QLDKev has said. More power more coil less water.

 

[Moad]

Thanks for the replies and detailed explanations. Learnt a lot on this thread in the past few days and as always appreciate the knowledge shared

 

[Adr_0]

In my experience the biggest restriction when it comes to flow is creating a vacuum and compressing your grain bed. You cannot infinitely turn up your flow. Best way is as QLDKev has said. More power more coil less water.

My point was more that the 809 will do everything comfortably...

 

[Tex N Oz]

Doesn't matter how you look at it, the maximum efficiency you can possibly get is:

4.186 J/g • K

Not accounting for any losses, which there is much.

 

[QldKev]

Thanks Kev,

I'm a bit confused, you say the proposed 10L/12m/2400w would be overkill but then say the herm-it coil you use is sufficient. Do you only use it to hold temps and not ramp or are you OK with the slower ramp times?

Your volumes are pretty much what I am after so would be very interested to get some more info on your setup. I am still making my way through this thread to hopefully not repeating questions already answered before.

I had no idea what was involved in designing a HEX/HERMS

The 10L/12m is the overkill for 2400w. Using a stainless coil, which stainless is not as good of a conductor as copper, the hermit only uses ~3m in ~2.5L for 3600w (max know). The idea is to find the amount of heat energy (watts) you need for your volume of mash, and then build a coil/water bath to match.

 

[TheWiggman]

The idea is to find the amount of heat energy (watts) you need for your volume of mash, and then build a coil/water bath to match.

Sound advice. The element will inadvertently be heating the mash liquor via the HERMS. The more power, the quicker the whole volume can be heated provided your HERMS coil is designed appropriately.

 

[Moad]

There are 6kw camco elements, so 7m in minimum amount of water with this element looks the go.

 

[mb-squared]

hey Moad, I have a 5.5kw camco in my HLT, which is where I have my HEX, and I'm able to get ~1.5F/min (Chugger pump, 50L HLT, 30~40L Mash depending on the recipe). If you go with a dedicated vessel for your HEX, you'll be able to go even faster I presume.

 

[Moad]

Cheers mb, I guess it will depend on flow rate with a 6kw. Will have to make sure the MT false bottom setup is up to the task. I've been looking at stout tanks but they are pricey!

 

[MastersBrewery]

You know you could go twin hermits, I would think getting flow rates high enough to have both using all their power might be the trick. I've seen a few stout setups with twin recircs though the $ for something like that would very quicky add up.

 

[QldKev]

There are 6kw camco elements, so 7m in minimum amount of water with this element looks the go.

Sounds awesome to me, even if you went anywhere from 7m up to 10m to be safe.

 

[Moad]

Thanks Kev, I've found lengths of 10 and 12m annealed copper. Would I beat best to go 12 or is 10 plenty in hour opinion?

 

[Adr_0]

So, the below is:
Blue - HLT/1V direct heating and well mixed. This represents the theoretical heat capacity/power curve, which is probably close to reality for a direct heated vessel.
Orange - 2m coil in 10L HEX, 13.5lpm
Red - 12m coil in 10L HEX, 10lpm


All used a 90L mash with a 7200W element.

Probably the most important thing to note is what the power does.
- For direct heating in the vessel, there is a constant demand on the power (blue line) and it drops off when it gets close to setpoint
- For the other two, once the coil outlet temp hits the setpoint (Coil T graph) the power drops off, so you are relying purely on turnover in the mash tun to bring your mash up
- For the short coil your HEX temp does go up a lot more (HEX T)

You could put a bigger element in manual for longer, but you would see your coil outlet temp go up a fair bit.

I will do some runs with different pump flowrates and different HEX volumes.

 

[QldKev]

Adr_0 that set of charts is awesome, really shows real world vs the theory. A couple of things I take from it. The longer coil hit the Coil T set point fastest, but the shorter coil was actually was slightly better in pushing the mash temp up. I guess that would be due to the increased flow rate due to the less amount of resistance. Thus transferring more heat into the wort, allowing the element to stay on longer. I would be interested in seeing runs with a 5m coil in 10L HEX, 12lpm? and also the 2m coil in 10L HEX, 13.5lpm run with 4800w I think the initial time will take longer before it switches off, but I wonder if it will effect the overall duration? Then another run with the 2m coil with a smaller water bath and 4800w.

Moad, after seeing Adr_0's real world numbers I'm thinking a shorter coil would be an option. If possible I would await Adr_0's testing as it is providing real world data.

 

[idzy]

Thanks Adr_0 - I have an 815 and an 809 and run neither at full flow, ever. I think we need some real world flow in these models too. Maybe choke down to 6-8lpm

 

[Adr_0]

Thanks Adr_0 - I have an 815 and an 809 and run neither at full flow, ever. I think we need some real world flow in these models too. Maybe choke down to 6-8lpm

Well, I have a 25L rectangular mash tun with a good manifold and run 7lpm with no dramas. 67% wheat and no rice hulls and no loss of flow/bed compression, so if a mash tun is 4 x the size - as long as the draw off area increases as well - are you saying 13lpm isn't possible? It might be tough with a tall, narrow mash tun.

 

[Moad]

Interesting Adr thanks for that!
Are there better pumps for this application given flow rate is such an important variable

 

[TheWiggman]

Agreed Kev, the difference in rate would be due to the change in flow. Note the temp of the HEx in comparison - the shorter coil approached boiling. Something to be wary of if going too short. I'm backing if the flows were identical in the model the response would be identical, the only difference being the HEx liquid temp.

 

[Adr_0]

Interesting Adr thanks for that!
Are there better pumps for this application given flow rate is such an important variable

Idzy has a good point in that we can't assume maximum flow through the grain bed with 20kg of grain in the mash tun, but the point of this is to illustrate just how important flow is. So your mash tun design will be critical and you need to consider the best way to achieve that flow.

I also made a bit of a gaff with my March pump gpm numbers, so more accurate numbers are below and have included 2m and 5m coils:


What I have modelled is still 7200W (sorry Kev):
Blue is 7200W, 90L well mixed single vessel
Orange is 10L HEX, 2m coil, and 19lpm. P control only, gain of 2.
Red is a 7L HEX, 5m coil and 15lpm. P control only, gain of 1.


Notice the better power usage but at the expense of some overshoot in the coil temp.

And for the record, 7200W with a 90L x 65 (3800J/kg.K / 60s) is a 1.25°Cmin theoretical, but 0.5°C/min actual (takes 20min to get from 65 to 75).

 

[Adr_0]

Sorry, knew there was something fishy... the red line is a P of 1, and a 5min Integral term. I don't think you'd ever be able to get this with auto-tune as it will just use P, I, D to get the coil temp bang on. So I included a bit of built-in overshoot. The catch with this is that it's dicing with a pretty fine line, i.e. how much do you trust the model?