Ramping Fast With A Herms? You?

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Yorg

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If you are ramping at greater than 1C per minute in a HERMS setup, what are the design elements that allow you to do it?

(Please don't turn this into a HERMS can or can't do step mashing - I've read enough on that elsewhere. I just want to hear from people who actually do step with it.)

Thanks.
 
Heat transfer in the HERMS vessel is increased by the following factors:

- Higher thermal conductivity of the coil material (copper > stainless steel here)
- Temperature difference between the wort and the thermal fluid *
- Movement of the thermal fluid in the HERMS vessel **
- Turbulence in the liquor coil ***

* Not as clear cut as "HERMS fluid temp - mash temp", the temperature difference will change throughout the coil as liquor temp will increase as it travels through. Also, the HERMS fluid at the tube surface will be lower than the bulk fluid as it is transferring heat to the liquor, see next point.

** Agitation of the fluid in the HERMS vessel yields a more uniform temperature all over the vessel (and at the coil surface).

*** Convoluting your HERMS coil can yield turbulent flow, mixing the fluid radially and resulting in more effective heat transfer away from the inner surface of the tube.
 
For a single batch (say 15-20L total mash volume)

With a 10L HERMS vessel I was able to get around 1C per minute (slightly less) ramp with a 2000W element. I stepped every time.

I have swapped to RIMS now and use the same 2000W element and get a better ramp rate of around 1C per minute (slightly more) - but better consistency and control. Once again, stepped basically every time.

Thats as good as commercial temp controlled mashes - and its good enough for me

In my sort of system - its mostly about element size and flow rates. HERMS vessel size is about speed of response, rather than total ability to change at a given number of degrees per minute.
 
I read in a text book once (Kunze I think), and have heard it in other places, that the rule of thumb for stepping temps, whether mashing or decocting, should be close to around the 1C/min increase mark.
 
My HERMS is about 5L with a stainless coil in it. I am not sure of the coil length. It has a 3.6kW element controlled by a PID temperature controller. The heatexchanger is full of water. Has anyone given any thought towards a water/???? mixture eg salt or alcohol?

The element is pulsed based on the recirculating wort temperature at the outlet of the coil. Once the wort is returned to the mash it will cool until enough has been recirculated to heat the whole mash up. I don't monitor the mash temperature, only the coil outlet. In the future I plan to monitor the coil inlet and the bottom, middle and top of the mash, but this will make little difference to my brewing procedure and is only for information purposes.

I am not sure of flow rate. If it is of interest I could work it out it based on the (height)head pressure versus flow rate graph. It is of little use to me.

I am still yet to experiment more but my HERMS can run at full flow and the coil outlet temp will slowly increase at approx or faster than 1deg/C or I can reduce the flow rate and the coil outlet temp will sit on the new temperature very quickly. Say 40degC --> 63degC in a matter of a minute or two. This doesn't mean that the mash has instantly gone to this temperature but the recirculating part has.

I normally run the recirculation at full flow rate. An improvement to this method for some beers that I want residual sugar in the profile would be to reduce to flow rate and denature the enzymes quickly through the heatexchanger.

Hope this helps.
 
I still can't understand, or should I say agree, with why some use the outlet as a proxy for measuring mash temp, rather than reading from within the mash - but that's another debate.
So you guys are saying that about 1C is what you get in mash ramp rate, and you are ok with that.
Still want to know if anyone is getting higher mash ramp than that, and how they are doing that.
Thanks so far guys.
 
Sorry, I might have been a bit confusing with my earlier post... From what i have read, stepping at a rate quicker than 1C/min is not such a good thing. I'm not sure what the defining limit is, but if you were getting 3C/min rise in your mash, I'm pretty sure you would be denaturing enzymes in your HERMS.

That brings us back to why most people measure the temp at the outlet of the HERMS. There is no point reading the temp in the middle of your mash when you are trying to heat a pretty big thermal mass by only heating a small amount of liquid at a time in your HERMS coil. By the time the thermal mass has reached the temp you want of around 65C, the temp of wort in your coil may have been reaching well over your desired sparge temp for some time.
 
For the guys using metal mash tuns could you drop a small flame (eg smallest ring on my 3 ring burner, or even the second ring) on under the mash tun, whilst also using the herms to heat. This way you would ramp up a lot quicker.

EDIT: The idea of adding additional heat from a small flame is trying to ensure no spo within the brew exceeeds the planned step temp. The running of the herms normally drains from the bottom of the tun so reducing the chance of the extra flame getting this area too hot.

PS. I dont run a herms, just an idea..



QldKev
 
Sorry, I might have been a bit confusing with my earlier post... From what i have read, stepping at a rate quicker than 1C/min is not such a good thing. I'm not sure what the defining limit is, but if you were getting 3C/min rise in your mash, I'm pretty sure you would be denaturing enzymes in your HERMS.

That brings us back to why most people measure the temp at the outlet of the HERMS. There is no point reading the temp in the middle of your mash when you are trying to heat a pretty big thermal mass by only heating a small amount of liquid at a time in your HERMS coil. By the time the thermal mass has reached the temp you want of around 65C, the temp of wort in your coil may have been reaching well over your desired sparge temp for some time.

Thanks for the reply.
I agree that given the same flow rate, getting a 3C ramp rate may result in quite hot wort coming out of the HEX. The question is, is wort at say 75C for 15 seconds going to denature enzymes enough? (It will only be overly hot for a short time until it reaches the mash tun and gives up its heat.) Probably worth avoiding this issue if possible.
The solution, I think, to a really fast ramp rate, without denaturing enzymes, is to increase the flow rate substantially.
Given that the element power and coil length are substantial also, a fast flow rate will mean the outlet of the HEX need only be modestly above the desired temp, allowing the quick turnover of wort to do the job of imparting temp quickly into the mash.
So, how can we improve the flow rate substantially?
This seems to be the bottle neck in current HERMS designs with regard to ramp rate.

For the guys using metal mash tuns could you drop a small flame (eg smallest ring on my 3 ring burner, or even the second ring) on under the mash tun, whilst also using the herms to heat. This way you would ramp up a lot quicker.

EDIT: The idea of adding additional heat from a small flame is trying to ensure no spo within the brew exceeeds the planned step temp. The running of the herms normally drains from the bottom of the tun so reducing the chance of the extra flame getting this area too hot.

PS. I dont run a herms, just an idea..



QldKev

Same issue, Kev. You can impart heat directly to assist the HEX, but the flow rate will determine if you are denaturing enzymes on the pan or not.
 
I asked the same question a little while ago, Yorg. The answers I got were that even if only raised above sach temps for a small amount of time, a certain percentage of the enzymes will be denatured. From what I have read, even if you came up with a way to raise the whole thermal mass of your mash (grain & wort) at a rate of substantially higher than 1C/min, this is not a good thing...

I guess at this point I would have to ask; What's the rush? We're only talking half an hour here if you do two 15 degree temp steps at 1C/min... Half an hour for better beer is a cheap price to pay...
 
If you want very fast steps you going to have to either decoct or make near boiling additions that presupposes a well stirred mash and I would be thinking mechanical stirrers, otherwise you have the same problem with hot spots killing enzymes.

The other half of the herms equation is the speed you can get liquor to pass through the mash, without pulling the bed. That pretty much gives you an upper limit on your flow rate from there it's a matter of how much heat you can add to that liquor without denaturing well we been there.

I think if you do all the numbers 1oC/Minute give or take, is really all your going to get without problems.

MHB
 
MHB is on the money I think. Flow rate has an in-built limiter in your grain bed.

You can add heat pretty fast, I have added at 2-3 per minute without issue by using a HLT with a large temperature differential. BUT - then you need to control your temps by measuring the mash bed (problems already discussed) and your control mechanism either has to be by routing the wort around the HLT via valves, or by not circulating continuously. I did this for a while, manually measuring the temps, and switching the pump on an off. Basically using the HERMS only for the purpose of stepping. But you have to constantly stir your mash tun, and it was bloody hard to hit temps accurately and without overshoot. So you had to creep up on them... all in all taking longer to actually hit the desired temp than with a more finely controlled system ramping at 1 per minute than the 2-3 mine was capable of at the time. So back to 1 per minute (ish) to avoid problems

There is no issue with ramping at 1 per minute anyway.... there isn't any need to ramp faster
 
Do most herms users crush a little coarser and add rice hulls to mae the circulation easier?
 
Yes I agree compaction of the bed is the ultimate cause - the limiter to flow rate, which is a limiter to ramp rate.
So my thinking is:
For HERMS, use a wider than conventional tun, increase the area of pass-through with a larger false bottom.
Say, for a doubling of the area, there should be a doubling of the flow rate acheivable before compaction becomes a problem, right?
(Or is my geometry/hydrodynamics understanding out?)

So for a 30cm falsie, like the one I have in my insulated cylindrical cooler, I would need to go to a 43 cm for doubling and a 52 cm for tripling of flow rate - which looks like being a practical max.

The next design issue to attend to then is the design of the return manifold, to ensure that the wort can be distributed evenly through the bed.
Any thought on what such a manifold should look like for say a 52 cm tun?
 
dependent on your mash tun design - you will also lose a lot more heat out of all the extra surface area

Darcy's Law for flowrates through a porous medium. Does not take compaction into account though. Most brewing texts work on teh assumption that you design your system to avoid as much compaction as you can (floating mash) , or you do something about it like install rakes (lauter tun)

Nonetheless - Given Darcy's law as a reasonable approximation you get a proportional increase in your flow rates with an increase in surface area.

I usually use a bunch of rice hulls in my mash - but I only have a braid false bottom, so therefore not great surface area. Enough of an issue so I have bought the gear for a new mash tun / FB set-up - BUT - a few drops of exogenous beta-glucanase in my last couple of brews.... and suddenly my flow rates jump. So thats the other thing you can do to increase your flowrates - decrease your wort viscosity (the mu symbol on the bottom of Darcy's law) by adding enzymes, choosing low beta glucan and/or low protien worts, or worts high in the relevant degredation enzymes and adding an appropriate temperature rest to allow their action.

A course crush would help too - or all of the above things added together.

Question still remains - that with perfectly conventional HB set-ups, you can ramp at 1 per minute, what advantage do you see in ramping more quickly than that? And if there is one, is it actually worth what you need to do to get it?
 

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