HERMS vs. "Counterflow" HERMS

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mightynintendo

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I am in the process of building a new brew rig, this time going with a two-tiered HERMS (Mash tun on top).

As I build and design the system, I am considering a few problems with HERMS and trying to see if there are some viable solutions.

The main problem I can see is temperature stratification in the HLT as it is heated from the bottom. Without adequate stirring, it will continue to be a problem. As a way to combat this, I thought perhaps it would be wise to recirculate my mash through a counter flow chiller, back into the mash tun, while recirculating the hot water from the HLT through the "cold water" side of the counter flow chiller.

The advantages of this, as far as I can tell:
  1. Eliminate the temperature stratification problem as the recirculation of the HLT water would provide constant stirring
  2. Would not need to drill as many holes in the HLT
  3. Would get more utility out of the copper needed in the chiller

However, some of the disadvantages I've considered are:
  1. Would need two pumps (at present I only have one)
  2. Possibly less energy efficient (would burn more propane)

Does anyone have any experience or advice on this? Are there any advantages and/or disadvantages I have not considered? Any input would be appreciated.
 
I'm no engineer, so this may be "out there", but I don't think it will work that well. The reason for recirculating/stirring the HLT is to avoid stratification. But sending water through the CFC to work as the HERMS may mean it's not able to hold temperature. You may find the water cooling to the mash, instead of raising/holding the mash at the HLT temperature. I hope that makes sense.

If you take the hottest water out, for example, from the bottom, the HERMS may be too warm. If you take the cooler water out from the side or top, the HERMS may not be warm enough and then the mash will "suck out" the temperature.

You want to recirculate the water in the HLT, or stir, or otherwise agitate. But the water being recirculated may not be the correct temperature is what I"m trying to say.
 
I'm no engineer, so this may be "out there", but I don't think it will work that well. The reason for recirculating/stirring the HLT is to avoid stratification. But sending water through the CFC to work as the HERMS may mean it's not able to hold temperature. You may find the water cooling to the mash, instead of raising/holding the mash at the HLT temperature. I hope that makes sense.

If you take the hottest water out, for example, from the bottom, the HERMS may be too warm. If you take the cooler water out from the side or top, the HERMS may not be warm enough and then the mash will "suck out" the temperature.

You want to recirculate the water in the HLT, or stir, or otherwise agitate. But the water being recirculated may not be the correct temperature is what I"m trying to say.

I think I see what you're saying. That basically my mash wort will cool my HLT water to the point that it won't be able to maintain its temperature. That would start a feedback loop that would result in unstable mash temps. Hmm.... so maybe i just need to buy the copper and the extra pump... I mean i don't really care to stand around and stir hot water for an hour (or more).
 
I think I see what you're saying. That basically my mash wort will cool my HLT water to the point that it won't be able to maintain its temperature. That would start a feedback loop that would result in unstable mash temps. Hmm.... so maybe i just need to buy the copper and the extra pump... I mean i don't really care to stand around and stir hot water for an hour (or more).

I have a little stirrer with a motor on my HLT. If you don't want to have another pump to just recirculate water, something like that could work.
 
We have done HERMS brews. We do have 2 pumps and the system is simple. We used pump the Wort into one side of a counterflow Chinchiller. We pumped hot water on the outside tube. We were able to maintain a constant temp without a problem. We use about a 5 to 10 degree difference between the HLT and the MLT as a starting guide. We recently purchased a Stout Conical HLT with HERMS but I had a tangential inlet installed so that I could "stir" the HLT water. Again, that would use the second pump. You can use a lower temp pump for the Wort as it does not get above 170 (or shouldn't).

We actually have 4 pumps but only use three. We need only one with the HERMS we have, but more pumps make it easier. We normally only move the "pump out" hoses and do not mess with the supply side. We prime all the pumps with just plain water before we brew and have lost most of our cavitaion problems by using full 1/2 inch flow on all fittings and use the short 3/4 inch silicone for the supply
 
I failed to mention that were just put the water back into the HLT. We just put it back with a hose and a copper spigot we made that could hang onto the lip of the HLT. We now use the tangential inlet and the HERMS coil sits in the HLT. The CFC worked as well as our new system and if I knew what I know now, I would keep doing it that way. We do use an inline trub filter from BrewersHardware in bot cases on the outlet side of the pump.
 
I think I see what you're saying. That basically my mash wort will cool my HLT water to the point that it won't be able to maintain its temperature. That would start a feedback loop that would result in unstable mash temps. Hmm.... so maybe i just need to buy the copper and the extra pump... I mean i don't really care to stand around and stir hot water for an hour (or more).

IMHO regardless of whether or not you use a CFC or a HERMS you are going to cool your HLT water with your mash. Both systems are heat exchangers and in order to heat your mash with HLT water, the HLT water loses energy to the wort and is cooled. The general idea is that you heat the mash slowly and consistently by varying the HLT temp. If you weren't heating the HLT for some reason then you would just dough in and recirculate through a heat exchanger to increase the thermal mass of the entire system thereby reducing heat loss over the mash duration.

Having said that I use a CFC with high temp tubing for the "cold side" as my mash heat exchanger. If you plan on using the mash heating water to sparge I wouldn't recommend using a CFC made with normal GH because of the potential to introduce GH flavor into your wort. I have had a lot of success using the CFC even without an automatic temperature controller for the HLT, I have to PWM it manually (which sucks) but it works for now.

If you want to do it on the cheap do what Yooper says and build a stirrer with an AC motor for the HLT, and install a HERMS coil. Then you can recirculate the mash with the pump and stir with the auto stirrer, leaving more time for drinking. :mug:

One other consideration with both HERMS and CFC heat exchangers is the possibility of grain husks getting through your false bottom. I use a SS washer hose braid and haven't had any problems with it. Just something to keep in mind.
 
RTL said:
IMHO regardless of whether or not you use a CFC or a HERMS you are going to cool your HLT water with your mash. Both systems are heat exchangers and in order to heat your mash with HLT water, the HLT water loses energy to the wort and is cooled. The general idea is that you heat the mash slowly and consistently by varying the HLT temp. If you weren't heating the HLT for some reason then you would just dough in and recirculate through a heat exchanger to increase the thermal mass of the entire system thereby reducing heat loss over the mash duration.

Having said that I use a CFC with high temp tubing for the "cold side" as my mash heat exchanger. If you plan on using the mash heating water to sparge I wouldn't recommend using a CFC made with normal GH because of the potential to introduce GH flavor into your wort. I have had a lot of success using the CFC even without an automatic temperature controller for the HLT, I have to PWM it manually (which sucks) but it works for now.

If you want to do it on the cheap do what Yooper says and build a stirrer with an AC motor for the HLT, and install a HERMS coil. Then you can recirculate the mash with the pump and stir with the auto stirrer, leaving more time for drinking. :mug:

One other consideration with both HERMS and CFC heat exchangers is the possibility of grain husks getting through your false bottom. I use a SS washer hose braid and haven't had any problems with it. Just something to keep in mind.

I sort of thought that but I wasn't sure whether the efficiency of a CFC was that much greater than a HERMS coil. If I go this route, I would definitely use an all-copper CFC. Though when sparing I imagine I would probably re route the hlt water away from the coil anyway.

What do you mean by PWM the pump manually?
 
Yooper, do you have a link for more info on your hlt stirrer?

No- but here are some photos:

DSCN0636.jpg

DSCN0637.jpg

DSCN0638.jpg

The fan is just to keep the motor cool for the stirrer. I didn't build it- it came with my system when I bought it. The "board" was added because it used to go through the top of the cooler lid that I used for an HLT back them and then I went with the keg HLT so I had to have a support for it.
 
just avoid the whole situation all together and build a dedicated HERMS pot... i never liked HLT-as-HERMS designs for this very reason, among others.





also working on a new one, out of stainless...
 
There are a few mentions in some posts here about using an aquarium air pump to agitate the HLT. I think the method is to attach a silicon tube to the air pump's output and submerge into the HLT. Or, I've seen someone mention attaching the air pump output to the HLT's sight glass tube. This seems to be a relatively non-intrusive method, assuming the agitation is adequate.

As for committing to an altogether separate heat exchange tank, I think that would be unnecessary given the cheap and simple solutions for temperature stratification in the HLT. Using the HLT as a heat exchanger provides the opportunity to use less water too. I like that idea.
 
Yah, I'll dig up the thread and link it at the bottom, but the air pump is exactly what I do. I didn't have a sight glass at the time, so I actually drilled a small hole in the bottom of the keg and put a weldless 3/8" fitting on it with a 90deg elbow and a barbed fitting. I run 1/4" tubing up the side of my keggle to the air pump that sits on my lid. It's really surprising, but that tiny stream of bubbles is enough to keep it thoroughly mixed.

The added bonus of this is that you can add a pressure sensor in the tubing and the rig then turns into a digital depth measurement. I haven't calibrated my pressure sensor yet, but it's on the to-do list for the next couple of brewing sessions.

https://www.homebrewtalk.com/f51/using-aquarium-air-pump-stir-hlt-surprisingly-works-195561/
 
mightynintendo said:
I sort of thought that but I wasn't sure whether the efficiency of a CFC was that much greater than a HERMS coil. If I go this route, I would definitely use an all-copper CFC. Though when sparing I imagine I would probably re route the hlt water away from the coil anyway.

What do you mean by PWM the pump manually?

PWM the element manually, not the pump. PWM stands for pulse width modulate and means you cycle something on and off to reduce the overall current, instead of varying the voltage.
 
Does anyone have any experience or advice on this? Are there any advantages and/or disadvantages I have not considered? Any input would be appreciated.

I just had my first run on it last weekend. Doing exactly as you described. Your thinking is very similar to what I'm doing and I had similar concerns. I don't have my automation of temps finished yet, so this was a "dumb" run of the circulation process, but I was very happy with the results. I should have PID automation in the next few weeks.

2012-09-08 11.05.07.jpg


2012-09-08 17.00.04.jpg
 
I'm also trying to work my RIMS tube in on the HTL side of the CFC HEX as a hybrid heat sorce. I also want to see how well it works to just use the RIMS tube and Counter Flow Heat Exchanger in a loop without the HLT.

2012-01-14 20.03.22.jpg
 
Wouldn't simply recirculating the hot water back to the HLT do the same thing? All my keggles are direct fired so I don't use a coil in my HLT but I do recirculate the HLT to maintain temps. Works well with no coil, I would assume it would at least help with a coil inside.
 
Wouldn't simply recirculating the hot water back to the HLT do the same thing? All my keggles are direct fired so I don't use a coil in my HLT but I do recirculate the HLT to maintain temps. Works well with no coil, I would assume it would at least help with a coil inside.

Sure. It's just that an extra pump is required, which is more expensive than an aquarium pump. So in a HERMS and single level system, you need three pumps instead of two.
 
I am thinking all this is over-complicating the issue. The temp of the wort coming out of the herms tube is what is important and if you are regulating your heat source via PID/controller off of that the control should not care about the heat stratification and it just wont matter as long as it can get the wort coming out at a consistent temperature.

I am running my eHERMs without any circulation of the HLT water and only using a simple temp controller and the temp coming out of the coil stays within 1 degree of my set point.

Please tell me where I am wrong?
 
HERMS using a CFC only requires two pumps for a single tier system. One recirculates the HLT and one recirculates the Mash.

When the HERMS coil is in the HTL, your mash temp is dependent on the temp of the HTL. You have to control the HLT temp closely and the temp in the HTL is directly related to the temp of the mash. There might be a few degree difference.

There is more control using the CFC. I keep the mash recirculating all the time. That helps to form a nice bed. I control the pump that recirculates the HLT through the CFC. If the mash needs to be hotter, I turn the pump on for the HTL. That moves heat from the HLT to the CFC which acts as a heat exchanger and heats the mash. If the mash is getting too hot, I just cut the pump to the HLT which immediately removes any heat source from the mash. The temp of the HLT doesn't matter as long as it's warmer than the Mash. I try to keep it at 170 sparge out temps.

I can also change the input to the CFC to cold water if I ever need to cool a mash, but hopefully that never happens.
 
HERMS using a CFC only requires two pumps for a single tier system. One recirculates the HLT and one recirculates the Mash.

But I have a stirrer, and when I only had one pump, I still was able to do this. If you have a stirrer for the HLT, you don't need a stirrer!

I had only one pump for ages and could batch sparge and do HERMS without any issues, since I could stir the HLT water.
 
HERMS using a CFC only requires two pumps for a single tier system. One recirculates the HLT and one recirculates the Mash.

When the HERMS coil is in the HTL, your mash temp is dependent on the temp of the HTL. You have to control the HLT temp closely and the temp in the HTL is directly related to the temp of the mash. There might be a few degree difference.

There is more control using the CFC. I keep the mash recirculating all the time. That helps to form a nice bed. I control the pump that recirculates the HLT through the CFC. If the mash needs to be hotter, I turn the pump on for the HTL. That moves heat from the HLT to the CFC which acts as a heat exchanger and heats the mash. If the mash is getting too hot, I just cut the pump to the HLT which immediately removes any heat source from the mash. The temp of the HLT doesn't matter as long as it's warmer than the Mash. I try to keep it at 170 sparge out temps.

I can also change the input to the CFC to cold water if I ever need to cool a mash, but hopefully that never happens.

I've a similar system. A one big advantage is that it's very fast. I'm getting 3C/min step's on mine (5kg mash) while using 80C HLT-water for the CFC. It's pretty hard to control though, I'm using 2 measuring points (wort + mash) and an Arduino to keep mash temp in control. I can keep the mash temp under 0.5C from the set temperature. https://lh5.googleusercontent.com/-Bppy6tm8pVc/ULQfRHdouMI/AAAAAAAAMXY/sLqH9uSrwRo/s912/cfctest6.jpg

I've build my own convoluted double copper CFC for the HERMS. It can be much shorter than what's needed for cooling the wort.
 
Nice work Vesku. Looks like you've got it under good control. What method are you using in the Arduino? PID or simple ON/OFF?

I need to finish my Arduino controller this winter.
 
A stir motor is the cheapest and easiest way to go unless you already have a spare pump laying around. I paid $15 for a 60rpm motor...

FEC89951.jpg


DB6FC50C.jpg
 
just avoid the whole situation all together and build a dedicated HERMS pot... i never liked HLT-as-HERMS designs for this very reason, among others.





also working on a new one, out of stainless...

I do this in a 2 gallon igloo cooler. Works beautifully.
 
I am thinking all this is over-complicating the issue. The temp of the wort coming out of the herms tube is what is important and if you are regulating your heat source via PID/controller off of that the control should not care about the heat stratification and it just wont matter as long as it can get the wort coming out at a consistent temperature.

I am running my eHERMs without any circulation of the HLT water and only using a simple temp controller and the temp coming out of the coil stays within 1 degree of my set point.

Please tell me where I am wrong?

Some things to think about. Do we even know how much of a temperature difference is going on with any given system design? Is it 20 degrees? Won't the copper or stainless coil also help carry the heat through the HLT?

Enough of a temperature difference could theoretically change the temperature of the wort enough at a certain point in the coil that the enzymes don't perform as expected. IMO uneducated mind, the likelihood of this happening is very slim. I imagine that once a wort reaches a stable temps, the temperature differential is not enough to be concerned with.

A larger diameter and shorter coil would obviously have less stratification going on than one which is narrow and tall. Therefore there may be more of an issue with the latter design.

That all said, there are several methods used to prevent stratification and most of them are very cheap and easy to use. So until there is sufficient data to the contrary, it would be wise to use one of those methods to prevent any problems.

I personally was intending to use a small food grade recirc pump mounted right on the side of the HLT. A car's window wiper motor would be great for operating a stirrer as well. They can be had for $15 or so at junk yards and are ready to run with a small 12V supply.
 
Nice work Vesku. Looks like you've got it under good control. What method are you using in the Arduino? PID or simple ON/OFF?

I need to finish my Arduino controller this winter.

I measure wort and mash temperatures and then calculate "offsets" for temperatures. Then just a simple "if switch" and a couple of cfc-pump on time limiting if's. No need for a PID and I don't know how complicated it would get with 2 probes and step mashes, probably complicated enough.... It's really easy to do it with Arduino, this was my 1st project ever. I use it for flow meter as well and I'm working on to add a scale to measure BK weight during the boil.
Here's the setup at the moment:
IMG_20121127_3503.JPG
 
Whoa! That electric connection over a pot of water in a keggle would make we want to wear "high voltage" protection equipment.
Yep, I do that also every time I use my tea kettle ;)

Seriously, it would easily pass IP6, probably even IP7 (30 minutes immersion at depth of 1 m) standard. And it's all behind a RCD, just in case....

The vertical element is great when doing the whirlpool. I had a horizontal in my previous kettle and that really sucked when it came to the whirlpool. I also get a way better boil with the vertical one, it's like a little geyser! Almost like mini-Merlin-kettle with out any hardware on the kettle.
 
Regarding the temp diff: I keep my HLT about 6 to 8 degrees higher than the desired Mash for a starter temp.

We normally heat our Mash water in the HLT, move to the MLT and get the MLT to the Strike temp (normally by adding a small amount of cold water as it is easier to cool than heat.) We then add some water to the HLT to get it down as we are over temp for the Herms.

It does take 2 pumps and that is more than one, but you know the saying: "Two is BETTER than one"!

We have Stout equipment and even my HLT has a tangential inlet.

Regarding stratification, I have 3 temp guauges on my MLT , 2 in the MLT and one on the input of the recycle. I control the temp on the recycle one and the rest will eventually be right there as well.
 
I've build HERMS with a dedicated HERMS-kettle. I had 2kw heating power (an induction stove) on it. I used a very small amount of water to get the response as fast as possible (1 quart). I made a hex-spiral rather than a coil, if you are wondering about the amount of water. It worked great, but it was too slow for step mashes. I could heat wort about 9C(16F) at best in-out from the hex-spiral at 2.5L/min flow. I got under 1C (1.8F)/min mash temp changes.
new%2520hx.jpg


With the CFC-HLT-HERMS I get up to 30C (54F) temperature difference between wort in - wort out and up to 4C(7.2F)/min mash temp change (90C(162F) HLT water).
cfctest6.jpg


Just compare the plots and see how fast the CFC-HERMS heats the wort even with "only" 80C(144F) water in the HLT.

The problem with the "HX-coil in HLT" is that you need to heat the whole kettle of water + mash to get your mash temp up and that's a really slow process. It's OK for single step mashes, but not so good, if a protein rest etc is needed.
 
I am thinking all this is over-complicating the issue. The temp of the wort coming out of the herms tube is what is important and if ...

...and the temp coming out of the coil stays within 1 degree of my set point.

Please tell me where I am wrong?

I agree, I think people are fixing a problem that may not actually exist. My system looks a lot like Yooper's without the mixer. When I start bringing my HLT up to temp I use my re-circ pump to draw water from the bottom and dump it on top to reduce any stratification at startup. However, once I hit strike temp, I set up my my HERMs coil without any regard to stratification and let it go. I have a thermo-well at the bottom of my HLT and take manual readings from the top and they never show a degree's difference. The MLT reads within a degree as well.

Granted, I haven't used this system in a cold environment yet so you northerners may have different results (I may too if we ever get a winter this year).
 
My own experience with staification came with an IC Cooler. Until I added a Jamil Tube and recycled the wort around the coil, it was not very efficent. I would assume the same on HERMS coil.
 
I know the problem existed on my system which is why I added the stir motor. The first 10 minutes of recirculation the temp would be stable and in line with my HLT, after that stratification would occur and the temp would drop a few degrees.

You have to remember that without the stir motor there is only a small drop in temp but when you are trying to raise your mash temp you want a steady temp rise with no drop. The stir motor cut about 15 minutes off of my mashout time.
 
Good stuff guys (and ladies). I'm glad I put off my build for a while to think about this and other issues.

As I consider it, recirculating the mash in a counterflow device with the hot liquor is essentially no different than the concept of a recirculating infusion mash system, except instead of using direct heat from an element, it would be using indirect heat from a heat exchanger. As Yooper stated, the problem that could arise is the hot liquor cooling to the mash temp more than the mash rising to the hot liquor. Although I am aware the second law of thermodynamics would insist that the heat would move from the hotter medium to the colder medium, the nature of a counterflow device would provide an exchange that results in an sort of equilibrium temperature between the two mediums, and getting the hot liquor to the correct temperature to provide the needed temperature support could prove quite challenging. Furthermore, the time required to raise the mash to mashout temps with such a system would be considerably longer than a RIMS system (because of the time required to raise the temperature of several gallons of hot liquor), thus making this method relatively inferior to the RIMS setup.

With that in mind, I think the traditional HERMS system is better than a "counterflow" HERMS system. Another pump is just going to have to happen. Not only will it provide recirculation for the hot liquor tank, but it will allow me to have all kettles on one level, pumping the hot liquor into the mash tun for sparging as I simultaneously pump the mash into the boil kettle. This way at least it is serving two purposes instead of the motorized stirrer which only serves a single function. While the rise time for mashout will still take a while (indicative of all HERMS systems), I will be avoiding the problem of having to fine-tune my hot liquor during each brew session using the counterflow method.

Also, I think I am going to go all electric. Makes for easier automation and doesn't fill my space with CO. It will also reduce the risk of setting my wood brew stand on fire with open flames.
 
My $0.02 is that you're over-complicating the issue. I run a HERMS coil in my HLT and simply use an in-line dial thermometer at the outlet of the coil before it returns to the top of the mash. I also have a temp probe in the HLT. I find that I need to run the temp of the HLT about 4 degrees warmer than the expected output off the coil but YMMV.

I don't have this system automated but it would be easy enough to do with an ASCO valve and pilot light system.
 
I've build HERMS with a dedicated HERMS-kettle. I had 2kw heating power (an induction stove) on it. I used a very small amount of water to get the response as fast as possible (1 quart). I made a hex-spiral rather than a coil, if you are wondering about the amount of water. It worked great, but it was too slow for step mashes. I could heat wort about 9C(16F) at best in-out from the hex-spiral at 2.5L/min flow. I got under 1C (1.8F)/min mash temp changes.
new%2520hx.jpg


With the CFC-HLT-HERMS I get up to 30C (54F) temperature difference between wort in - wort out and up to 4C(7.2F)/min mash temp change (90C(162F) HLT water).
cfctest6.jpg


Just compare the plots and see how fast the CFC-HERMS heats the wort even with "only" 80C(144F) water in the HLT.

The problem with the "HX-coil in HLT" is that you need to heat the whole kettle of water + mash to get your mash temp up and that's a really slow process. It's OK for single step mashes, but not so good, if a protein rest etc is needed.

This is one of the single best posts on HERMS design implications. Fantastic post and truly appreciated from someone who is a single upgrade away from going HERMS.


Adam
 
Although I am aware the second law of thermodynamics would insist that the heat would move from the hotter medium to the colder medium, the nature of a counterflow device would provide an exchange that results in an sort of equilibrium temperature between the two mediums, and getting the hot liquor to the correct temperature to provide the needed temperature support could prove quite challenging. Furthermore, the time required to raise the mash to mashout temps with such a system would be considerably longer than a RIMS system (because of the time required to raise the temperature of several gallons of hot liquor), thus making this method relatively inferior to the RIMS setup.

I will be avoiding the problem of having to fine-tune my hot liquor during each brew session using the counterflow method.

You're confused on the counter-flow HERMS process. I don't control the HTL temp, I just want it to be pretty hot so it has more thermal energy to transfer to the Mash. 180F to 200F is fine and you can do that manually. You do want to avoid boiling so you don't get bubbles in the line. I've found that the recirculation will pull enough heat out to avoid a boil.

What I control is the pump that recirculates the water in the HLT. When I reach the Set Point for the Mast, that pump is turned off. No heat is transferred to the Mash as it rests. When the Mash cools and needs more heat to stay at the Set Point, then the HLT pump is turned on. During the whole rest time when the pump was off, the burner or heating element can still be running on the HLT. That adds heat back into the HLT to recover what was transferred to the Mash when the pump was on.

You do not need to maintain your HLT temp at your Mash Set Point. You want the HLT HOT so it has a lot of thermal energy ready to transfer to the Mash when needed.

Here's a temp ramp I recorded on an untuned test run just to see it work using a turkey fryer burner under the HLT with 10 gallons. 2.1 F per minute. I think I can make that much faster with a little tinkering.

counterflow-herms-temp-ramp-57458.png


I did a later test with a 5500W element that I didn't record that took the Mash from 66F to 170F in 18 minutes. 5.8 F per minute. Another run was 66F to 150F in 12.25 minutes. 6.8 F per minute. That's with a 10 gallon HTL and 10 gallon Mash.
 
This is one of the single best posts on HERMS design implications. Fantastic post and truly appreciated from someone who is a single upgrade away from going HERMS.


Adam

Thanks, I've put a lot of hours on this, hopefully it saves someone the trouble of testing things. I've had almost all HERMS-systems I've seen anywhere and I think that the CFC-herms is the best without any question. Only big down sides are the difficulty of the temp control + need of the 2nd pump.

I'm still trying to find the best control settings, here's a plot of a real mash that I made yesterday (60mins 50C, 45mins 62C, 45mins 66C, mash out 74C):
munich1mash.jpg

There's a lot more overshoots compared to the test plot without grains. Grains are a really hard thermal mass to simulate.... I've another mash going on now with improved control sketch. The biggest problem to me is to how to measure the mash temp accurately. There's so big temp differences on the mash when it's heating up that it makes the controlling a really difficult task to do especially with really hot wort coming from the herms. I've been thinking to add a few temp sensors in different parts of the mash and averaging it to get better results (Arduino is great for this sort of stuff, so easy and cheap to add sensors etc.). I also use more water in the mash now to get a sort of buffer in the mash tun to protect the grains in the top from overheating.

Yes, my main hobby is making brewing gear, don't even really care if it makes the beers better or not :D Then comes beer drinking and after that the brewing.
 
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