Reverse HERMS

[QldKev]

Something I've been thinking about for a while and another thread has prompted me to put this up. I'll call it a reverse HERMS. It's reverse as the coil goes into the mash and fresh hot water is recirculated through it. The same reverse HERMS / heat box then can double for both the mash and the HLT heating requirements.

Benifits
Only one set of heating elements is required for both HLT and HERMS
Reverse HERMS / heat box could just be a kettle with inlet and outlets plumbed into it.
No wort contact for the heating element (removed possibility of scorching / burning elements etc)
Only fresh water is pumped through the HERMS coil. Easier to keep clean.
Mash coil doubles as an immersion chiller.
Mash coil helps heat more uniformly.
Instant cutoff of heating, no temperature overshoot due to thermal mass in HERMS unit. In this case water just stops flowing.
No need to holes for heating elements in the main vessels.
Option to push a second coil in the HLT meaning no water from inside the coils touches brew water/wort.

Drawbacks
Second pump is needed to recirculate mash. Pumps are not that expensive.
You would not want the solenoids switching at SSR speeds. But I do not think you would not need to.
You would need a couple of liters of water at all times in the HLT. In my case I keep some water there for clean ups anyway.
Option to remove the solenoid and have a second pump keeping the HLT and mash flow separate. Not sure if this is worth while.

Other thoughs
Solenoid block may allow either flow to happen. When the mash needs heating it flows through there. Otherwise the HLT can get the hot water. If there is enough heat potential in the reverse HERMS both outlets may be able to flow simultaneously.
Possibly leave the pump and HLT open always, and only switch the flow through the mash as needed.


A second option....
Don't have a reverse HERMS box and flow water from the HLT through the coil in the mash tun.

The downside to this is the thermal mass of the HLT may make ramping slow as the HLT cannot exceed the set temperature for it, whereas the separate HERMS can jump up above the desired temperature range to push ramp rates faster. ie. When a ramp to mashout is required, the HLT is set to 77-78c. So the water going to the mashtun coil will not exceed this temperature. With the first idea, the heat box may get up to 90c making the change in temperature faster. Also the heating is heating both the HLT and mash at one time making it slow.

 

[gava]

I'd think you'd get inconsistent temps through your MASH since the heating coil will be heating whats around it and not whats near the wall of the MLT.
So in the middle you'd have 65c but near the walls you could be 10+c less which will probably result in crap efficiency.

Good for thinking outside the square but personally I think this wouldn't work very well.

my 2c

Gav

 

[QldKev]

This is a discussion thread, just an idea. The mash would still be recirculated via a second pump, I noted the second pump as a drawback maybe I should have drawn it in there. So rather than hotter wort being poured at the top and sucked down through the mash, this way you would have more uniform heating from the coil, and the recirculating wort would have less difficulties to even it out. That's my thought anyway.

 

[Parks]

I really don't see it working at all. It takes long enough to raise mash temp with a hand held element let-alone a coil where the max temp is 100 deg C

 

[gava]

This is a discussion thread, just an idea. The mash would still be recirculated via a second pump, I noted the second pump as a drawback maybe I should have drawn it in there. So rather than hotter wort being poured at the top and sucked down through the mash, this way you would have more uniform heating from the coil, and the recirculating wort would have less difficulties to even it out. That's my thought anyway.

Ah, I didn't read it like that... That would help yes...

interesting Idea.

Although I'd love to see the results of this one..

 

[GalBrew]

I think you would need a big ass coil in the mash, and a constant mash recirculation to keep the temp in the mash more uniform and eliminate any temperature gradients in the mash. Not sure you would get ramp times as quick as a normal HERMS?

 

[pk.sax]

Yeah, had the similar idea but to use the herms to boil the kettle. As said above, max 100C in the coil won't heat that quick, neither would it boil so quick in my case unless using some heating system that goes well above.

Centralised heating would be awesome if achievable on the home scale. I mean, do we really need a HLT for a full volume 1v/2v mash...

 

[TheWiggman]

I think the issue you would run into is ramp times. Consider the priciples around thermal conduction which relate primarily between your conductivity and temperature difference. The higher the difference in temperature, the faster the rate of change of temperature. Consider these points -

1. Assuming that the temperature is already 78°C in your HLT, as soon as this transfer takes place to the MLT the temperature will increase in the MLT and decrease in the HLT. This will then mean the HLT will need some form of control system to compensate, which could be something simple like an STC-1000 or whatever. In any case there's a good chance the temperature once it reaches the MLT will be lower than your desired 78°C.
2. As the MLT gets closer to the desired temp (let's say 67°C) the rate of change will slow. This is only a 11°C difference so when you're getting close to this there is not much thermal energy available in the flowing liquid to transfer in your coil.
3. If the coil was infinitely long in your MLT, the temp of the water coming out will be equal to the temp of the mash tun. Thus, if you are limiting your HLT temperature you are only able to transfer a certain amount of 'energy' to the MLT will be directly related to the overall 'conductivity of the coil' in the HLT. This incorporates surface area, material condcutivity, flow rates etc.

If you think about these points it is desirable to have a higher temp in your heat exchanger (HERMS water) than the desired temp of the mash liquor. In reality what should happen is there is a big difference between your HERMS temp and MLT temp - where the MLT draws energy from the HERMS, in turn cooling it down - and as you get close to the set temp the temperature the two converge until they are essentially equal.
I think there is scope for your concept, but I don't think it would be as effective as desired.

 

[Parks]

I think the issue you would run into is ramp times. Consider the priciples around thermal conduction which relate primarily between your conductivity and temperature difference. The higher the difference in temperature, the faster the rate of change of temperature. Consider these points -

... clipped for brevity ...

That's what I said :lol:

 

[MastersBrewery]

This has been discussed before in Nev's hermit build thread, the pump he supplies, was re wired by a member that enabled it to work in either direction specifically for this application. I'll do my best to find some links for you guys
MB

 

[Parks]

This has been discussed before in Nev's hermit build thread, the pump he supplies, was re wired by a member that enabled it to work in either direction specifically for this application. I'll do my best to find some links for you guys
MB

Nope - that's quite a different concept.

That was about turning your herms setup into "reverse flow" the same as how a braumeister works. This is running hot water through a coil in the mash.

 

[MastersBrewery]

ahhh gotcha, so which is called what then?

 

[Parks]

Not sure either have a name set in stone.

I would call the other one in Nev's thread a reverse flow HERMS. This... I don't know

 

[TheWiggman]

That's what I said :lol:

Yeah I was at work and hiding the screen when people walked by. You posted while I was writing.
Then I saw that Kev already said what I said. Doh!

The second idea would be much more effective. Heat up the HLT, start the pump and keep the heater on until ideal temp is reached. With the first idea you're heating two pots at the same time, hence longer ramps.

Got a spare pot and chiller around QldKev? Why not give it a go?

 

[QldKev]

I really don't see it working at all. It takes long enough to raise mash temp with a hand held element let-alone a coil where the max temp is 100 deg C

Why would this system be any different to a traditional HERMS for heating times. The water in my HERMS does not exceed 100c, even with the element on 100% duty. The advantage here is we can have a longer coil without having a larger HERMS volume.

Yeah, had the similar idea but to use the herms to boil the kettle. As said above, max 100C in the coil won't heat that quick, neither would it boil so quick in my case unless using some heating system that goes well above.

Centralised heating would be awesome if achievable on the home scale. I mean, do we really need a HLT for a full volume 1v/2v mash...

I don't think this will work for the kettle. In the design above I've limited it to HLT and mash tun only.

I think the issue you would run into is ramp times. Consider the priciples around thermal conduction which relate primarily between your conductivity and temperature difference. The higher the difference in temperature, the faster the rate of change of temperature. Consider these points -

1. Assuming that the temperature is already 78°C in your HLT, as soon as this transfer takes place to the MLT the temperature will increase in the MLT and decrease in the HLT. This will then mean the HLT will need some form of control system to compensate, which could be something simple like an STC-1000 or whatever. In any case there's a good chance the temperature once it reaches the MLT will be lower than your desired 78°C.
2. As the MLT gets closer to the desired temp (let's say 67°C) the rate of change will slow. This is only a 11°C difference so when you're getting close to this there is not much thermal energy available in the flowing liquid to transfer in your coil.
3. If the coil was infinitely long in your MLT, the temp of the water coming out will be equal to the temp of the mash tun. Thus, if you are limiting your HLT temperature you are only able to transfer a certain amount of 'energy' to the MLT will be directly related to the overall 'conductivity of the coil' in the HLT. This incorporates surface area, material condcutivity, flow rates etc.

If you think about these points it is desirable to have a higher temp in your heat exchanger (HERMS water) than the desired temp of the mash liquor. In reality what should happen is there is a big difference between your HERMS temp and MLT temp - where the MLT draws energy from the HERMS, in turn cooling it down - and as you get close to the set temp the temperature the two converge until they are essentially equal.
I think there is scope for your concept, but I don't think it would be as effective as desired.

Think of the solenoid block in the original pic as a T piece and then 2 valves, one on each outlet.
So the reverse HERMS/heat box will only heat one at one time.

So if the mash needs heat it only heats that one vessel. The HLT valve is closed. All heat goes to the mash and the mash will heat as quick as a standard HERMS with the HERMS water potentially exceeding 78c (same as a typical HERMS may).

Then once the mash is up to temperature, the mash valve closes and the HLT if it needs heating will open his valve. Once again the water coming from the HERMS may exceed 78c.








So overall the mash is still being recirculated by a second pump full time. This will clarify the bed and distribute the heat.

 

[Mardoo]

Why would this system be any different to a traditional HERMS for heating times. The water in my HERMS does not exceed 100c, even with the element on 100% duty. The advantage here is we can have a longer coil without having a larger HERMS volume.

I believe that would be because of the ratios of the thermal mass involved. The thermal mass of the water in your HERMS is much greater than the thermal mass of the volume of wort in your coil at any given time. However the thermal mass of the water in your reverse HERMS coil is much less than the thermal mass of your mash.

 

[dent]

Yeah I already used the "Reverse Herms" term - "Backwards Herms" is still free if you want it.

I don't think it is a terrible idea. I think the best point of your system, which I don't think was mentioned, is that during the initial stages of the mash, where it is all gluey with starch etc and most likely to jam up, we can still heat the mash and get it converting so it flows nicely by the time you get to lautering. So in the end maybe you could run a thicker mash and maybe get some bigger batches for container size. Or go nuts with sticky adjuncts.

 

[TheWiggman]

Think of the solenoid block in the original pic as a T piece and then 2 valves, one on each outlet.

I completely misunderstood your concept. For some reason I thought the HLT water was flowing though the HERMS > MLT > solenoid > HLT. Wrong.

I take back what I said, I reckon the idea is fine. Slightly lower ramp times due to the heat exchanger in the mash, but probably negligible. Could be addressed with a long heat exchanger or smaller OD pipe.
I use the HERMS in my system to heat my strike water, this would be no different.

 

[QldKev]

Yeah I already used the "Reverse Herms" term - "Backwards Herms" is still free if you want it.

I don't think it is a terrible idea. I think the best point of your system, which I don't think was mentioned, is that during the initial stages of the mash, where it is all gluey with starch etc and most likely to jam up, we can still heat the mash and get it converting so it flows nicely by the time you get to lautering. So in the end maybe you could run a thicker mash and maybe get some bigger batches for container size. Or go nuts with sticky adjuncts.

How about UN-HERMS

Large % of sticky adjuncts is where the idea is actually originated from

 

[Not For Horses]

If you're only pumping hot water rather than mash, you could use 6mm tube. Heaps more surface area for the same volume of water being pumped.