# Reverse HERMS



## QldKev (12/2/14)

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 (12/2/14)

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 (12/2/14)

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 (12/2/14)

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 (12/2/14)

QldKev said:


> 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 (12/2/14)

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 (12/2/14)

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 (12/2/14)

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 -


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.
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.
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 (12/2/14)

TheWiggman said:


> 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 (12/2/14)

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 (12/2/14)

MastersBrewery said:


> 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 (12/2/14)

ahhh gotcha, so which is called what then?


----------



## Parks (12/2/14)

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 (12/2/14)

Parks said:


> 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 (13/2/14)

Parks said:


> 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.




practicalfool said:


> 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.





TheWiggman said:


> 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 -
> 
> 
> 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.
> ...


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 (13/2/14)

QldKev said:


> 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 (13/2/14)

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 (13/2/14)

QldKev said:


> 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 (13/2/14)

dent said:


> 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 (13/2/14)

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.


----------



## Not For Horses (26/2/14)

How do you reckon this would go for heating green malt during the conversion phase for crystal malt?

The idea being that you want to take wet green malt from the floor at ~16 degrees and heat it to 72 with minimal water used in the 'mash' to retain all the sugars inside the kernel thus maintaining a high extract value for the finished product.


----------



## QldKev (26/2/14)

Not For Horses said:


> How do you reckon this would go for heating green malt during the conversion phase for crystal malt?
> 
> The idea being that you want to take wet green malt from the floor at ~16 degrees and heat it to 72 with minimal water used in the 'mash' to retain all the sugars inside the kernel thus maintaining a high extract value for the finished product.


I think it would work great


----------



## Beerisyummy (16/5/14)

Did you end up trying this QldK?


----------



## QldKev (16/5/14)

Beerisyummy said:


> Did you end up trying this QldK?



Nope not yet, Beer projects are on hold due to other hobbies currently consuming my time and money. The only issue I have thought about is with the coil in the mash it will be harder to give it a thorough stir.


----------



## Beerisyummy (16/5/14)

No probs. I'm brewing later today with something similar. Time will tell.

I think you've used a similar pot within a kettle for the mash? I could be thinking of someone else. Anyway, the whirlpool and recirculation seem to do away with stirring for me. Efficiency is great with a sparge.

cheers.


----------



## RelaxedBrewer (16/5/14)

This is a really interesting idea. 

One problem that might be an issue is that the heating coil will be in contact with actual grain. This may cause scorching of the grain.

I am going to into this further as I am trying to work out the best temperature control and ramp/step heating setup for my large system. The length of coil for the heat transfer is really appealing.

edit. on further thought. Where would you measure the temperature of your mash from?


----------



## stux (16/5/14)

HEIRMS - heat exchanger in recirculating mash system

CIMRS - (simmers) coil in mash recirculating system


----------



## Beerisyummy (18/5/14)

The ICHE - RIM maybe? :unsure: Immersion Coil Heat Exchanger - Recirculating Infusion Mash. No scratching allowed!

For anyone interested, I did a run with my set up on Friday and the results were promising. It's a 1v rig (sort of) with a small boiler used to supply hot liquid to the immersion coil.
As long as you have your grain contained in something along the lines of a malt pipe, the coil can be used to heat the mash water as well as chilling during the whirlpool.

A couple of observations:
- The system was really simple to control with an STC1000. My PID was unavailable, so I just tossed the STC probe in the same as the coil which did not cause any overshoot, although I think luck helped with the settings.
- Ramp times were almost identical to the other HE methods I've tried thus far. After 3 test runs and 1x 40l batch I'm convinced it should work consistently.
- With 15m of liquid filled coil and only enough water to cover the element, there was very little lag time when powered up.
- Cleaning was extremely easy and all parts in contact with the wort can be visually inspected before and after use.
- A LBP was enough to run the boiler system and coil. The little bugger handled 110c for a half hour as well.
- I was able to get 35L of water boiling in the kettle (during the last test run) after playing around with the boiler fluid. Unfortunately, I only have one LB pump which stopped me from testing higher temps.
- 35L of water being boiled by a 15m long element ( the coil) does not look normal. The pot looked like it was full of "Schweppervescence".

Based on the above, I can't see why you couldn't supercharge a small boiler to feed several remote coils. I'd imagine a coil inside the actual mash wouldn't work very well, but any moving liquid works just fine.

All a bit of fun if you like tinkering.


----------



## TheWiggman (18/5/14)

Got any pics beerisyummy?


----------



## QldKev (18/5/14)

Sounds great for a first run of a completely new idea. 
The comment about _"Cleaning was extremely easy and all parts in contact with the wort can be visually inspected before and after use."_ I think is a great point.
You mentioned you don't think it would work if the coil was in the grain, but what if the mash itself was being recirculated via another pump? That would ensure the wort is continually mixing.

A standard immersion chiller, a LBP and a $8 kmart kettle for an easy way to control mash temps, and the coil doubles as the chiller.


----------



## Beerisyummy (18/5/14)

QldKev said:


> Sounds great for a first run of a completely new idea.
> The comment about _"Cleaning was extremely easy and all parts in contact with the wort can be visually inspected before and after use."_ I think is a great point.
> You mentioned you don't think it would work if the coil was in the grain, but what if the mash itself was being recirculated via another pump? That would ensure the wort is continually mixing.
> 
> A standard immersion chiller, a LBP and a $8 kmart kettle for an easy way to control mash temps, and the coil doubles as the chiller.


Access for cleaning was what got me started on this experiment. The 30 plate chiller that I'd been using as a heat exchanger really had me worried. I looked at an easy way to jacket the bottom of my kettle and eventually decided the coil was a better design.

It's just my gut feeling about the coil not working in the grain bed. I guess if you had a really fluid slurry of grain, or extremely good flow through a grain bed the recirculation might be enough. I just think the heat transfer will be too slow.
The idea definitely warrants further investigation.

There was about 10L of clear runnings whirlpooling around the coil before being pumped up through the grain bed to recirculate. This way the boiler fluid never exceeded the runnings temperature by more than 17c.
That means the hottest parts of the 15m coil were never very hot, which was totally different in my old set up. Instead of very hot runnings being recirculated back into a cool mash this way the whole thing is very gentle.

Some other ideas I had for coil placement were under a false bottom or in the layer of water/ wort above the grain bed. The recirculation might be enough to get effective heat transfer. I figure it's someone else's turn to do some tests on that one. I won't be brewing again for a few days.




TheWiggman said:


> Got any pics beerisyummy?


That I do! I even got one of the coil boiling the kettle.
Give me a while and I'll get them posted up.


----------



## Beerisyummy (18/5/14)

Pics as promised.

First one shows the coil I made. There is a tee half way down to split the coil in two halves. The general idea was that cooling water can go down to the outer tee and spread the cooling goodness. When I use it for heating the heated water is directed down to the inner tee which should give less flow restriction to the lower coil, just in case the top is above the liquid during the mash.




This is the cradle I use to pump water up through the mash. The next pot nestles onto it and gravity seals it all up. I have thought about making a few subtle changes to this part put it works well enough.



This is the part that holds the mash. 5- 6kg is a good size grain bill as is, for more I use a longer rod and add the offcut from the cradle as an extension collar.



All this drops neatly into the 50L pot and coil. The insulated lid fits snuggly over the top but I was yet to widen the side opening in this shot.



Add water, slowly add the grist while stirring and you're ready to put on the screens. 3kg of wheat and 2 kg of PPils in this time.



Three modified Ikea spatter guards. First is the glass type (with the glass removed) as a seal and then the two mesh types. It works and the parts were easy to source cheaply.



Turn it all on and walk away. If you get a stuck sparge from a fine grist it simply pops the mash pot up out of the cradle. reversing the flow for a bit will normally fix this or you can just use a sensible grind setting.



After the boil I simply kept the whirlpool going while running cold water through the coil. 15mins later it all got covered up and left to settle before draining in to the FV.



This shot is the 35L of water fizzing from the coil. I was only game to push the LBP to 110c during this experiment so it was a gentle boil. The whole thing looked like a big tub of soda water in the flesh.



Enjoy guys.


----------



## Adr_0 (18/5/14)

dent said:


> 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.


Actually I was wondering how you do your initial dough in?

And everyone is saying differential temperature is needed - and it is - but don't underestimate flowrate. If you have flow on both sides of the tube - and it looks like you do - and have the pumps to do it, that will do massive things for your ramp speed.

As Not For Horses said, narrower ID tube is best. I actually think 3/8 is the ideal as you get about 40% more power than 1/2" for the same flowrate and differential. On that same theory 6mm should be good, but you might lose pressure/flow with any decent sort of length and go backwards... unless you have awesome pumps.

If you get stuck, maybe try the AdRIMS...
*trolling*


----------



## Beerisyummy (18/5/14)

Dent or me?

I think the narrower ID tube will totally stuff the flow rate, although I'm willing to snag some tube and try. It really comes down to the available pumps IMO.


----------



## Adr_0 (18/5/14)

Beerisyummy said:


> Dent or me?
> 
> I think the narrower ID tube will totally stuff the flow rate, although I'm willing to snag some tube and try. It really comes down to the available pumps IMO.


Doing the initial dough-in... QldKev actually.

Yes, my gut feel is 6mm is too narrow but I have had great joy with 3/8" tube in the past mostly due to the higher velocity. I'm ignoring the poor availability of 3/8" fittings....

This is particularly the case for using garden hose for immersion chilling, for e.g. and 3/8" makes a measurable difference on 1/2". Unfortunately while higher velocity = more power, higher velocity = higher pressure drop so your pump has to be able to manage a decent flowrate with more back pressure on it. It will balance out somewhere, but my gut feel is that for 6mm tube it will be too low in the flow and any benefit you get from increased velocity will be negated. Somebody can run the hydraulic calcs, not me...


----------



## TheWiggman (18/5/14)

Looks the goods beerisyummy. It looks like you're just pumping water, how did you manage to get it up to 110°C? The water's boiling though, so hot it was. 
Adro, where did you get that number from (40%)? Not sure what you mean by power. Pipe diam won't affect power, only efficiency of thermal transfer. 
I crapped on about it in the HERMS thread, but thinner pipe does not necessarily equal better efficiency. For a given flow rate, assuming flow is fixed, the larger diameter pipe the better. For a given velocity, the opposite is true. Now because we're talking small centrifugal pumps, the narrower the pipe the lower the flow, and hence going a smaller pipe has a bit of a compounding effect. But to maximise transfer, more flow is better. Thus larger pipe is better for a GIVEN LENGTH in this scenario.


----------



## TheWiggman (18/5/14)

Adr_0 said:


> This is particularly the case for using garden hose for immersion chilling, for e.g. and 3/8" makes a measurable difference on 1/2". Unfortunately while higher velocity = more power, higher velocity = higher pressure drop so your pump has to be able to manage a decent flowrate with more back pressure on it. It will balance out somewhere, but my gut feel is that for 6mm tube it will be too low in the flow and any benefit you get from increased velocity will be negated. Somebody can run the hydraulic calcs, not me...


Sort of right. The specifics of the theory is right, but we're talking centrifugal pumps. Larger diameter = less pressure loss due to viscosity. Fewer losses = less pressure or 'head' on the pump, which equals more flow. 
Never forget this - low discharge pressure = more flow for centrifugal pumps. 
I could do the maths but it's a ball tearer and any change in flow requires a lookup to a Moody chart and a recalculation of the whole thing. Also, you're referring to velocity incorrectly - you meant flow when talking power. More flow means more power spent. These little pumps don't care about back pressure, nor do most centrifugal pumps. They just draw less power and internally recirculate more.


----------



## Adr_0 (18/5/14)

TheWiggman said:


> Sort of right. The specifics of the theory is right, but we're talking centrifugal pumps. Larger diameter = less pressure loss due to viscosity. Fewer losses = less pressure or 'head' on the pump, which equals more flow.
> Never forget this - low discharge pressure = more flow for centrifugal pumps.
> I could do the maths but it's a ball tearer and any change in flow requires a lookup to a Moody chart and a recalculation of the whole thing. Also, you're referring to velocity incorrectly - you meant flow when talking power. More flow means more power spent. These little pumps don't care about back pressure, nor do most centrifugal pumps. They just draw less power and internally recirculate more.


When I say 'power' I mean heat removed (joules/cal) per second - sorry, should have clarified that. 

The 40% I worked out about 10-11 years ago halfway through doing my degree. It was basically about 20% extra due to the velocity, and about the same again for the extra turbulence. Both of these essentially just move fresh fluid to the contact surface. It is well accepted in the industry, with the trade off being increased pressure drop.

Which is where we agree: centrif pumps do go back on their curve with more back pressure, so it has to be balanced and you need the pump curve for this. Generally the beefier pumps have decent flow and aren't that sensitive to back pressure.


----------



## TheWiggman (18/5/14)

Righto. Make sure you differentiate between flow and velocity - for a fixed flow, larger diameter means lower velocity so this changes the situation. You can't just talk about velocities in this scenario because it's driven by a pump. 
If you care, I have the formula out of a heat transfer text book which shows the relationship between diameter and temperatures to determine your heat transfer convection coefficient. Can't do it now due to phone. 
Make sure you pour a glass of your best home brew prior to reading though - it's riveting stuff.


----------



## Burt de Ernie (18/5/14)

Kev,

Dropping the coil into the mash was what Rinnai build one had going. I had approximately 7 meter of 3/4 copper coil in the mash tun. (Notice the 3/4 mustard colour pipe dropping in to the mash tun below). I found the ramp times were not too desirable even running the Rinnai at 85 degrees.





The current setup I have could easily be incorporated into your 2 option which would give you good ramp times and this can be done running 75 degrees.


----------



## Beerisyummy (19/5/14)

TheWiggman said:


> It looks like you're just pumping water, how did you manage to get it up to 110°C?


I was in a small town where Propylene Glycol was unavailable. $0.65 worth of table salt ended up being the easiest solution at the time.

BdE, there seems to be a human head protruding from your mash tun!


----------



## Adr_0 (19/5/14)

TheWiggman said:


> Righto. Make sure you differentiate between flow and velocity - for a fixed flow, larger diameter means lower velocity so this changes the situation. You can't just talk about velocities in this scenario because it's driven by a pump.
> If you care, I have the formula out of a heat transfer text book which shows the relationship between diameter and temperatures to determine your heat transfer convection coefficient. Can't do it now due to phone.
> Make sure you pour a glass of your best home brew prior to reading though - it's riveting stuff.


I probably have the same textbook...






To translate:
- The governing equation is q (heat transferred per second) = h (heat transfer coeff) x Area x diff T
- 3/8" tube has 27% LESS heat transfer capacity than 1/2" based on Area only - makes sense and most people understand this
- 3/8" tube however has 76% HIGHER heat transfer coefficient due mostly to the increased velocity and turbulence
- 3/8" tube OVERALL (when these factors combine) can transmit 28% more heat power per metre for a given flowrate than 1/2" tube

3/8" tube is also cheaper, but unfortunately fittings are a bit annoying to find - you can braze 1/2" fittings on without a drama though.

As I said in a previous post, this is well understood in the industry (gas processing, refining, chemical processing, LNG) but always has to be weighed up against pressure loss in the pipe. This is particularly relevant to centrif pumps and you need the pump curve from the manufacturer (or do a bench test) and then you can use your hydraulic calcs to see where the system will operate on the pump curve.

Anyway, let's get this back to reverse HERMS....


----------



## Adr_0 (19/5/14)

And I guess the application to reverse HERMS is not to underestimate how important flow is IN and AROUND the tubes.

So hammer it through the tube - as long as your heat can keep up - buy also make sure you get good flow through the grain bed. This with a decent temp difference will help your ramp time. 

When you first said 'reverse' I thought you might have drawn from the top of the bed and pumped in to the bottom. Probably great for mash/lauter efficiency and heat transfer buy probably not the best for grain bits in your pump. You would also need a pump with a fair bit of suction lift.

If anyone has a system like that, I would love to see it...


----------



## Parks (19/5/14)

Adr_0 said:


> When you first said 'reverse' I thought you might have drawn from the top of the bed and pumped in to the bottom. Probably great for mash/lauter efficiency and heat transfer buy probably not the best for grain bits in your pump. You would also need a pump with a fair bit of suction lift.
> 
> If anyone has a system like that, I would love to see it...


This is something like what I am planning. My plan is to have flow reversible so I can prime the system normally then reverse the flow for herms. Then when it gets to mash out temp go back to normal for clarification.


----------



## Beerisyummy (19/5/14)

Parks said:


> This is something like what I am planning. My plan is to have flow reversible so I can prime the system normally then reverse the flow for herms. Then when it gets to mash out temp go back to normal for clarification.


That's pretty much what I do. The efficiency and clarity is great using this method. No stirring needed.


----------



## Adr_0 (19/5/14)

Parks said:


> This is something like what I am planning. My plan is to have flow reversible so I can prime the system normally then reverse the flow for herms. Then when it gets to mash out temp go back to normal for clarification.


Awesome...


----------



## S.E (19/5/14)

QldKev said:


> 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.
> 
> 
> 
> ...


Your first drawing is the same as a domestic hot water and central heating system as used in colder climates only the reverse HERMS in your drawing would just be a boiler (no coil inside) and the flow pumped from the top outlet and return to the bottom. Your mash tun would be the hot water cylinder and the HLT would be a radiator (or radiators in each room).

I have built lots of central heating and hot water systems for myself, friends and family back in the days when everyone installed their own solid fuel or gas boilers and re wired their own houses. 

I had thought but never got around to doing something similar with my brewery so will be interested to hear how you get on with this. My plan had been to use my brew kettle to heat all the mash and sparge water first then pump some to the mash tun and re circulate the sparge water through a copper pipe snaking back and forward flat on the bottom of the MT just above the manifold or FB to maintain mash temperature while using a second pump to re circulate the mash. Then when the mash was finished pump the sparge water from the kettle to the HLT.

Cheers Sean


----------



## TheWiggman (19/5/14)

Adro, it's valid indeed for HERMS or reverse as selection of pipe is one of those thumbsuck things where you're safer going more than less. The result could be twice as much real estate taken up by the HERMS tube.
The maths was right in your example but there is an issue with the application of the Dittus-Boelter equation for the Nusselt number. Assuming a different equation was used, this would change the result completely.

I might rasie a new thread about this for the eggheads and maybe knock up a spreadsheet to do the calcs for critical review.

What's super-critical though is like you said is flow over the reverse-HERMS coil. This will have a massive impact on the efficiency of the HERMS. If put straight on the grain bed without flow (which is not how beerisyummy's system operates, fortunately for him) there will be slower ramp times, hot pockets and the measuring point for the temp control will have a huge bearing on the system design.
The only other way I think this could be addressed is through a recirc system. Or maybe a running mash paddle?


----------



## Adr_0 (19/5/14)

TheWiggman said:


> Adro, it's valid indeed for HERMS or reverse as selection of pipe is one of those thumbsuck things where _*you're safer going more than less*_. The result could be twice as much real estate taken up by the HERMS tube.
> *I can't tell you how many times in my career as a process and project engineer we have replaced pumps, control valves, flowmeters and water pipelines because somebody has thought 'bigger is better'. The key is that you have you evaluate the system in place. If you want to apply safety factors, understand the impact they may have on the system. *
> 
> The maths was right in your example but there is an issue with the application of the Dittus-Boelter equation for the Nusselt number. Assuming a different equation was used, this would change the result completely.* You are welcome to try as many correlations as you like - make sure you post your results for everyone to see. Don't forget the pump curves.*
> *And if you're talking laminar flow, remember this is like trying to get a faster boil by turning the heat down on your burner.*


----------

