HERMS Coil

[allgrainpa]

I am attempting to convert 2 keggles into a herms HLT and MT. I have been looking at many different set-up options. I am wanting to build a SS Herms coil with triclamp fittings. The Stout Kettles look awesome and I would love have one but the wife is not going to allow me to drop that kind of cash. Plus this is what makes homebrewing great, tinkering and building/upgrading your own system.

I contacted Stout kettle company (conical-fermentor.com) and asked about the diameter, size and length of their herms coil. They informed me for a 15 gallon tank they use 3/8 tubing diameter of coil of approx. 6" in coiled diameter and used approx. 31 ft of coil, stainless steel of course.

Wanted everyone's opinion and their input. Is there a "magic" number of coils the heat exchanger that will offer the best heat exchange? Has anyone had problems with 3/8" OD in regards of grain getting stuck inside the tubing?

All input and opinions welcome.

 

[Smellyglove]

Herms efficiency is something for the mathematically skilled people, I'm unfortunately not one of them.

The factors I can think of right of the bat are:

How much liquid will there be in your HLT when you use your herms? Remember that when you ramp up the temp, the wort flowing through the coils works against your heating element in the HLT, since it has a lower temp than the temp you're trying to reach. This is the most important factor if everything else is according to the "book".

Higher flow means less heat exchange directly to the wort running through the coil. But since its a closed system I reckon the result will be approx the same timewise.

Higher flow means you pull more "dirt" through the system, and get less clear wort (my experience).

 

[BadWolfBrewing]

I have the stout coil, the 8mm, which is the actual inner diameter, is too small. At full throttle, my center inlet chugger can only get about 1.25 gpm, which isn't fast enough for my system.

Are you using an insulated mlt? That makes a big difference, as the heat exchanger doesn't have add much work to do.

I have a stainless mlt, and it the mash temperature really lags the hlt. I have learned to compensate for it, but a faster flow would fix things.

Talk to zach at stainlessbrewing.com and tell him what you want. He builds custom coils for less that I can even find the raw materials for.

 

[BadWolfBrewing]

Also, faster flow means more heat exchange. Don't let anybody else tell you otherwise.

 

[Smellyglove]

Also, faster flow means more heat exchange. Don't let anybody else tell you otherwise.

How can this be correct? If the wort spends less time in the herms-coil, it will not get as heated as wort spending more time in the coil.

Edit: This discussion will show up in the thread, so I'll jumpstart it:

The slower flow the more heat is being applied to the wort in the herms coil. Even it if spends more time, it will not get any hotter than your set temp. If it doesn't spend enough time in the coil it will not get warmed up to your set temp. So the optimal flow would be where the wort has reached your set temp just as it exits the coil.

Here comes one of the funny things: Since it's a closed system, the same wort will travel through your coil over and over again.
The higher the flow, less heat get exchanged to it, since it stays in the area of heat exchange for a smaller amount of time. It's like putting your finger on the stove, the longer you keep it there the more your burn your finger. Less flow means more heat gets to it.

But like I said, since it's a closed system, and if you have a good insulated mashtun, "all" on the heat-energy stays within the system. So you can pick your choice. High flow = more trips through the herms-coil, less flow = fewer trips through the coil, the result should be the same, as it is a closed system where the energy/heat applied stays within it.

Please correct me if Im wrong, but this seems logical.

 

[ChocolateMaltyBalls]

Flow depends on the coil length. The longer the tube the higher flow you can use. You want higher flow so you get your mash volume thru the coil and heated quicker.

I spot check the coil out put every once in a while, and since I recirculate wide open (after setting the grain bed) it is usually below the set temp at first. But it recirculates fast enough to over come the coil inefficiency, and come to mash temp in a reasonable time.

I find the key is not to rely on the HERMS to get to mash temp, but only to maintain. I use strike water to get close to mash temp then let the coil get it the rest of the way.


Sent from my iPhone using Home Brew

 

[Smellyglove]

I find the key is not to rely on the HERMS to get to mash temp, but only to maintain. I use strike water to get close to mash temp then let the coil get it the rest of the way.


Sent from my iPhone using Home Brew

Agreed. If I'm brewing alone I dump all the grains in at once, meaning I need a strike temp of 4C above mash temp. If I have a buddy over we'll stir the grains in slowly, then I don't have to think about mash temp vs strike temp.

 

[allgrainpa]

Bad wolf:

What size system do you have? The stout coil is this being used in a custom stout kettle or did you place a stout coil in an alternate vessel?

 

[BadWolfBrewing]

The stout coil was included with the 20g stout tanks HLT.

Don't get me wrong, I'm still able to make beer. But steps like mashout take longer than I'd like. At steady-state, i.e., once the system has settled and temps stop changing, the MLT is about 1.5 degs. F below the HLT. I an live with it, I'd just like it to respond to changes in the HLT faster. The flow rate is what causes the lag.

Heat transfer is wonky stuff, and non-intuitive until you've been forced to study it. Everybody on these forums has some expertise. There's biologists that talk about yeast slants, welders that build beautiful brew stands, etc... I have a doctorate in mechanical engineering, with an emphasis on controlling electromechanical systems. So, thats the part of the hobby that I really get into.

The rate of heat transfer is proportional to the difference in temperatures. Picture flowing through a HERMS coil at just a trickle. Within a couple feet, the temp in the coil is equal to the temp in the HLT. Once that happens, you aren't actually adding any energy to the fluid in the coil.

Now speed up that flow. Eventually, the exit wort is less than the HLT. Though non-intuitive, this is actually a good thing. This means that you were getting more thermal energy into the fluid.

Here's where somebody could point out that even if the rate at which energy was transferred from the HLT to the wort in the coil is increased, the wort is moving faster so it doesn't get to feel the effects of the increased rate for as long. So the pro and the con cancel out.

If there was a finite amount of liquid that we could move through the heat exchanger and we wanted to get as much heat transfer out of it, then yes. Slow down as much as possible.

Our situation is different though, as we are continuously pumping more liquid into the coil. That liquid then returns to the MLT, and we keep pumping more. The coil is always full. The higher the log mean temperature difference between the coil and the HLT liquid, the more heat transfer we get.

The other benefit to flowing faster is increased turbulence. The heat exchange coefficient increases with turbulence. That is the 'selling point' of the convoluted tubing. Though our flow is already pretty turbulent, so aside from more surface area I doubt it helps much.

As long as you aren't overly compacting the grain bed, you'll do better the faster you flow.

Hope that wasn't too long / boring. There's a fair amount of misinformation floating around on this forum on the whole heat transfer topic.

 

[Smellyglove]

The stout coil was included with the 20g stout tanks HLT.

Don't get me wrong, I'm still able to make beer. But steps like mashout take longer than I'd like. At steady-state, i.e., once the system has settled and temps stop changing, the MLT is about 1.5 degs. F below the HLT. I an live with it, I'd just like it to respond to changes in the HLT faster. The flow rate is what causes the lag.

Heat transfer is wonky stuff, and non-intuitive until you've been forced to study it. Everybody on these forums has some expertise. There's biologists that talk about yeast slants, welders that build beautiful brew stands, etc... I have a doctorate in mechanical engineering, with an emphasis on controlling electromechanical systems. So, thats the part of the hobby that I really get into.

The rate of heat transfer is proportional to the difference in temperatures. Picture flowing through a HERMS coil at just a trickle. Within a couple feet, the temp in the coil is equal to the temp in the HLT. Once that happens, you aren't actually adding any energy to the fluid in the coil.

Now speed up that flow. Eventually, the exit wort is less than the HLT. Though non-intuitive, this is actually a good thing. This means that you were getting more thermal energy into the fluid.

Here's where somebody could point out that even if the rate at which energy was transferred from the HLT to the wort in the coil is increased, the wort is moving faster so it doesn't get to feel the effects of the increased rate for as long. So the pro and the con cancel out.

If there was a finite amount of liquid that we could move through the heat exchanger and we wanted to get as much heat transfer out of it, then yes. Slow down as much as possible.

Our situation is different though, as we are continuously pumping more liquid into the coil. That liquid then returns to the MLT, and we keep pumping more. The coil is always full. The higher the log mean temperature difference between the coil and the HLT liquid, the more heat transfer we get.

The other benefit to flowing faster is increased turbulence. The heat exchange coefficient increases with turbulence. That is the 'selling point' of the convoluted tubing. Though our flow is already pretty turbulent, so aside from more surface area I doubt it helps much.

As long as you aren't overly compacting the grain bed, you'll do better the faster you flow.

Hope that wasn't too long / boring. There's a fair amount of misinformation floating around on this forum on the whole heat transfer topic.

since you're the man to ask, and I suck at these things.

Can you confirm my thought that the perfect flow rate is when the wort has reached the set temp of the herms, just before it exits it? or am I wrong?

 

[allgrainpa]

Bad wolf:

So it sounds like you invested in a stout kettle system. Are you continuing to use stout HLT even if your unhappy with the system response to temp changes? And I'm I following you correct by stating if stout would use a different HERMs cool the system would be responsive and over all better system?

I contacted stout concerning their coil for this exact reason and to get everyone's input before I lay down a large amount of cash.

 

[BadWolfBrewing]

it depends on your goal. In something like chilling (cfc or IC), I'd say there is a reason to conserve water. So, as the wort gets closer to pitching temps, slowing down the flow so that it takes less water to cool the wort further.

In mash recirculation, you will get the most heat transfer with the highest possible flow. The flow rate is in my case limited by a narrow HERMS coil. If that wasn't an issue, it would be limited by the maximum lauter rate, i.e., pulling liquid from the mash without compacting the grain bed. I would guess on my system that is between 2 and 3 GPM.

Any forced convection heat transfer works that way. Think of the wind chill effect. The faster the cold air is moving, the more heat transfer from you to the air. Or blowing on hot food. The faster you blow, the faster it cools.

All we are interested, in the recirculation case, is keeping the HLT and MLT as tightly coupled as possible.

1. The more flow rate through the coil the better, although you will get to a point of diminishing returns (i.e., increasing the flow a crazy amount won't make much more of a difference).

2. The more you agitate or recirculate in the HLT, the better. Again, there will be a point that increasing it won't make much of a difference.

3. Finally, the surface area of the heat exchanger will increase how tightly coupled the HLT and MLT are. This is also affected by the flow rate though. Think of the care you described where the coil egress is at the HLT temp. Increasing the length of the coil doesn't help you, even though you are increasing the surface area. Increasing the diameter, on the other hand, increases the surface area while also decreasing the flow resistance. Increase the diameter too much, and the flow is laminar instead of turbulent, and so the increased surface area actually hurts you a little.

I keep meaning to write up an article and submit it to HBT about temperature control systems and heat transfer, but haven't gotten to it.

 

[BadWolfBrewing]

Bad wolf:

So it sounds like you invested in a stout kettle system. Are you continuing to use stout HLT even if your unhappy with the system response to temp changes? And I'm I following you correct by stating if stout would use a different HERMs cool the system would be responsive and over all better system?

I contacted stout concerning their coil for this exact reason and to get everyone's input before I lay down a large amount of cash.

Yep, I have the whole 20g system, all electric with a Kal-type panel.

I exchanged a few emails with John about the coil back when I first received the system last summer. The coil could be improved in a number of ways.

1. It is very tightly coiled. This also decreases the flow rate, as a tightly coiled pipe has much more resistance to flow than a straight pipe. This also means that the HLT liquid 'inside' the coil and the liquid 'outside' the coil are very separated. When I first started using it, this caused major problems as I wasn't getting a lot of agitation in the entire HLT volume. I fixed this by adding a tee so I can shoot the recirc water both inside and outside the coil. That made a big difference.

2. The coil is very tall (see point 1). After I transfer the strike water to the MLT, sometimes I need to add more water back to the HLT just to keep the coil submerged. This water addition is probably not as hot as I'd like, so I have to wait while it warms up.

3. It is 8mm tubing, which is also very restrictive.

4. The coil was raised to allow a heating element to fit under it, which is good. It was raised REALLY HIGH though, something like 6 inches. At approximately 1 inch per gallon, if the height of the coil was only raised 3 inches, it would require a lot less water to keep the coil under water

That looks like a lot of complaining, but the system really does work just fine. The MLT tracks within 1.5 F of the HLT, which is really all that matters. Having it get up to temp a little faster would be nice, but it isn't a deal breaker.

Aside from thinking the coil could use some improvements, I'd say my other complaint is the domed bottom of the boil kettle. The tangential inlet is great, and I can get a hell of a whirlpool going. There is a ton of dead-space though, and I have to tilt the kettle a fair amount when transferring to fermenters to avoid leaving almost 2 gallons behind. It wouldn't be a huge deal, but I brew by myself and I only have so many hands.

That all being said, I would order them again. The bottom drain in the MLT is fantastic, the construction is very sturdy, I like the false bottom a lot, and they come with all the hardware you need

 

[allgrainpa]

yes I am talking in regards of mash recirculation. In the stout 15 gallon tank they use roughly a 3/8" OD coil. If you were to use a 1/2" OD coil then you could run the water faster thus improving efficiency of mash recirculation, got it. Now like you mentioned the next factor is how fast you can lauter. Your system can move 2-3 GPM? What type pumps are you using?

Does the stout kettles use, again roughly, 3/8" diameter ferrules inlet/outlets throughout the HLT and MT design? This would appear to be a flaw in their design.

The effect of using 1/2" coil would make your herms coil larger in diameter in the HLT and with all the triclamps, thermometer probe, inlet/outlet fittings room appears to be limited. Do you think this is why they chose 3/8" tubing? they informed me that their coil diameter is only 6" which makes a nice compact herms coil which appears nice.

Would you recommend a STOUT designed HLT, MT and BK?

 

[BadWolfBrewing]

Bad wolf:

So it sounds like you invested in a stout kettle system. Are you continuing to use stout HLT even if your unhappy with the system response to temp changes? And I'm I following you correct by stating if stout would use a different HERMs cool the system would be responsive and over all better system?

I contacted stout concerning their coil for this exact reason and to get everyone's input before I lay down a large amount of cash.

Not sure I answered your question, even in all that text. I get wordy after I've had a pint.

Yes, I still use it. I've done 6 batches on it, and I have the hang of it. A better heat exchanger would make things easier, like not having to refill the HLT to keep the coil under water, or get to mashout temps faster. It doesn't effect the quality of the beer at all, just adds steps /time to the brew day.

I'm considering making a new straight piped counterflow heat exchanged out of copper to double as a HERMS HEX and CFC. I need a CFC, and if I can get double use out of it than all the better. To be perfectly honest, half the reason to build it is probably because I like having something to work on.

Insulating the MLT would make a lot of problems go away too. Not a good reason, I guess, but I like their appearance a lot and don't want to cover them up.

I'm happy to answer specific questions about the system, or take pics or measurements or whatever too.

 

[BadWolfBrewing]

yes I am talking in regards of mash recirculation. In the stout 15 gallon tank they use roughly a 3/8" OD coil. If you were to use a 1/2" OD coil then you could run the water faster thus improving efficiency of mash recirculation, got it. Now like you mentioned the next factor is how fast you can lauter. Your system can move 2-3 GPM? What type pumps are you using?

Does the stout kettles use, again roughly, 3/8" diameter ferrules inlet/outlets throughout the HLT and MT design? This would appear to be a flaw in their design.

The effect of using 1/2" coil would make your herms coil larger in diameter in the HLT and with all the triclamps, thermometer probe, inlet/outlet fittings room appears to be limited. Do you think this is why they chose 3/8" tubing? they informed me that their coil diameter is only 6" which makes a nice compact herms coil which appears nice.

Would you recommend a STOUT designed HLT, MT and BK?

My pumps, the center inlet chuggers, can really move a lot of liquid if there isn't the flow restriction. The 2-3 GPM I was referring to was how fast you can lauter without causing a stuck sparge. I'm just guessing at the number. At a little over 1 GPM, I still have a pretty loose grain bed. So, with a bigger pump or less restrictive coil, I think I could recirculate faster before having problems.

Only the coil is < 3/8", the ferrules are all plenty big for a homebrewer. Just eyeballing, I'd say about an inch, ID.

A bigger coil with bigger tubing would fill up more of the HLT, that is true. I think there is room for it though. I think somebody ordered a replacement coil from www.stainlessbrewing.com to fit the stout HLT with 50' of 1/2" stainless tubing. Not sure how it turned out though.

Yep, I like mine a lot. The little problems are not deal breakers.

 

[allgrainpa]

2 questions for bad wolf:

#1 are you badWolf Brewing located in manassas, va I ask because your bio lists Madison, wi as your location.

#2 this may be a dumb question but im not sure I know what a herms hex coil is. CFC stands for counter-flow chiller and I know and understand what a CFC is well but not a "herms hex".

Again thanks for taking your time and answering my questions

 

[BadWolfBrewing]

2 questions for bad wolf:

#1 are you badWolf Brewing located in manassas, va I ask because your bio lists Madison, wi as your location.

#2 this may be a dumb question but im not sure I know what a herms hex coil is. CFC stands for counter-flow chiller and I know and understand what a CFC is well but not a "herms hex".

Again thanks for taking your time and answering my questions

Hah, no I'm not that brewery. I did see them on the internet though. I had to change the name of my 'brewery', so as to not copy them when I etched pint glasses

Actually, I'm in Detroit now, but moving to South Bend in a few months.

HERMS is heat exchange recirculating mash system. HEX is shorthand for heat exchanger. I've seen pics of people using the CFC to heat the mash liquid. HLT water flows through the outer pipe, the wort flows through the inner pipe

 

[allgrainpa]

gotcha.

I would love to see pics of your system. How long have you been brewing?

 

[Smellyglove]

Please. Can someone tell me why you get your entire mash heated faster if you have a flow which is high?

 

[BadWolfBrewing]

Please. Can someone tell me why you get your entire mash heated faster if you have a flow which is high?

One way to look at is the faster you flow, the less time it takes to get all of the mash liquid through the heat exchanger.

Say you have 10g of wort. Is you flow at 0.5 gpm, it takes 20 minutes for the entire wort to pass through. If you flow at 2 gpm, it takes 5 minutes.

I know it isn't that simple, as the mash liquid is continuously being mixed as you recirculate, but it is a reasonably accurate concept.

The simple yet factual answer is, the heat transfer coefficient for forced convection increases with flow rate. Think of a little cylinder of water traveling through the coil. The amount of energy transferred from the coil wall to that small volume is proportional to the temperature difference between the cylinder of water and the tubing wall.

If you slow the flow way down, the temp of that little volume quickly matches that of the tube wall. So, for most of its trip through the coil it isn't doing much to help. If you speed the flow up, it will have a greater difference in temperature for all of its trip, so it will exchange more energy.

The usual conclusion is that because a slow flow means that the egress of the coil is at the HLT temp, then maximum heat transfer was achieved. I guess it was, if you are only concerned with heating up the wort in the coil. But you have gallons sitting in the mash tun, just waiting to get themselves through the coil as well. By flowing faster, you get all that volume through the coil sooner. And as that volume goes through, you are heating up the entire mash, and eventually the mash liquid coming out of the coil will be near the HLT temp.

To summarize a long point, just because you've achieved great heat transfer to the little amount of fluid in the coil doesn't mean you are doing a good job of getting that heat into the mash vessel quickly.

Sorry if that isn't more clear, this is tough stuff to explain. Here's an online calculator where can play with the numbers. Just put in something close to our values, and try different flow rates. I'm not sure it is accurate for our class of heat exchangers, but the relationship to flow rate will be there.

http://www.engineeringpage.com/cgi-bin/he/h_tube.pl

If I think way back to undergrad, the heat transfer course was one of the hardest that we had to go through.

 

[BadWolfBrewing]

gotcha.

I would love to see pics of your system. How long have you been brewing?

Coming up on 5 years or there abouts. Started on a stove top with my grandpa, and really got into it.

Here's a few shots. I tried to show the herms coil, and how I split the water return into two paths

 

[allgrainpa]

Bad Wolf:

nice picks. Are all three vessels 20 gallons look like some might be different sizes. Do you mind telling me the sizes of each vessel, ie BK 20 gallons, HLT 10.

Thanks again for your time in this matter. I want to learn as much as possible about STOUT kettles and everyones input that has ir is currently using them.

 

[BadWolfBrewing]

They are all 20. The boil kettle has a skirt to allow for the domed bottom, and the mlt has a skirt to allow for the bottom drain. The hlt doesn't have a skirt so it sits lower.

No prob, happy to help

 

[Smellyglove]

One way to look at is the faster you flow, the less time it takes to get all of the mash liquid through the heat exchanger.

Say you have 10g of wort. Is you flow at 0.5 gpm, it takes 20 minutes for the entire wort to pass through. If you flow at 2 gpm, it takes 5 minutes.

I know it isn't that simple, as the mash liquid is continuously being mixed as you recirculate, but it is a reasonably accurate concept.

The simple yet factual answer is, the heat transfer coefficient for forced convection increases with flow rate. Think of a little cylinder of water traveling through the coil. The amount of energy transferred from the coil wall to that small volume is proportional to the temperature difference between the cylinder of water and the tubing wall.

If you slow the flow way down, the temp of that little volume quickly matches that of the tube wall. So, for most of its trip through the coil it isn't doing much to help. If you speed the flow up, it will have a greater difference in temperature for all of its trip, so it will exchange more energy.

The usual conclusion is that because a slow flow means that the egress of the coil is at the HLT temp, then maximum heat transfer was achieved. I guess it was, if you are only concerned with heating up the wort in the coil. But you have gallons sitting in the mash tun, just waiting to get themselves through the coil as well. By flowing faster, you get all that volume through the coil sooner. And as that volume goes through, you are heating up the entire mash, and eventually the mash liquid coming out of the coil will be near the HLT temp.

To summarize a long point, just because you've achieved great heat transfer to the little amount of fluid in the coil doesn't mean you are doing a good job of getting that heat into the mash vessel quickly.

Sorry if that isn't more clear, this is tough stuff to explain. Here's an online calculator where can play with the numbers. Just put in something close to our values, and try different flow rates. I'm not sure it is accurate for our class of heat exchangers, but the relationship to flow rate will be there.

http://www.engineeringpage.com/cgi-bin/he/h_tube.pl

If I think way back to undergrad, the heat transfer course was one of the hardest that we had to go through.

I get you, thanks.

I know there is no point in having the wort staying in there longer than it takes for it to get heated to the temp you want it.

I thought the most effective flowrate would be so that the small cylinder of water inside the coil has reached the temp just as it exits the coil. Then no heat is being "wasted" and the water has absorbed most possible heat.

 

[BadWolfBrewing]

I get you, thanks.

I know there is no point in having the wort staying in there longer than it takes for it to get heated to the temp you want it.

I thought the most effective flowrate would be so that the small cylinder of water inside the coil has reached the temp just as it exits the coil. Then no heat is being "wasted" and the water has absorbed most possible heat.

Like I said, it is counter-intuitive. Here's a new way of looking at it.

Ignore the coil for now, and just think of two vessels that share some common walls. Which is more or less true, though the wall they share happens to be coil shaped...

You want to maximize the amount of heat exchange between the two. So, you try and maximize the surface area (the wall they share) and you try to get some flow in the vessels.

This flow is important, as anybody who has tried an IC with and without stirring / whirlpooling knows.

By getting a good flow in the vessels, you are turning natural convection into forced convection. If you don't flow, the wort next to the shared wall heats up and prevents new colder wort from also getting next to the wall so it can also heat up. If you get the liquid moving, there's always some cooler wort next to the shared wall, so you are always getting the most heat transfer between the 2 vessels.

It sounds odd, but just treating the coil like a shared wall between vessels is perfectly accurate, and it might make the heat transfer concepts more intuitive.

I found this paper too:
http://www.solarenergy.ch/fileadmin/daten/publ/EuroSun2010_Logie_ERRATA_SECURE.pdf

On page 6 they show some experimental results from changing the flow rate. They use mass flow rate, or an m with a dot over it. In all cases, higher flow = high heat transfer coefficient

 

[Smellyglove]

Like I said, it is counter-intuitive. Here's a new way of looking at it.

Ignore the coil for now, and just think of two vessels that share some common walls. Which is more or less true, though the wall they share happens to be coil shaped...

You want to maximize the amount of heat exchange between the two. So, you try and maximize the surface area (the wall they share) and you try to get some flow in the vessels.

This flow is important, as anybody who has tried an IC with and without stirring / whirlpooling knows.

By getting a good flow in the vessels, you are turning natural convection into forced convection. If you don't flow, the wort next to the shared wall heats up and prevents new colder wort from also getting next to the wall so it can also heat up. If you get the liquid moving, there's always some cooler wort next to the shared wall, so you are always getting the most heat transfer between the 2 vessels.

It sounds odd, but just treating the coil like a shared wall between vessels is perfectly accurate, and it might make the heat transfer concepts more intuitive.

I found this paper too:
http://www.solarenergy.ch/fileadmin/daten/publ/EuroSun2010_Logie_ERRATA_SECURE.pdf

On page 6 they show some experimental results from changing the flow rate. They use mass flow rate, or an m with a dot over it. In all cases, higher flow = high heat transfer coefficient

Alright. Thanks for all your input.

So, if the wort which exits the coil is as hot as it can get, it then have more energy and transfer some of this energy to the colder wort in the mash tun, it doesn't help (as much) on the time it takes to heat the whole wort?

I was under the impression that since it's a closed system with a finite amount of wort, and you put x amount of energy into it, it will still reach the target temp as fast as with a higher flow. The difference being where the cold wort gets it heat from (directly from the coil or from hotter wort).

I'm not arguing here, Im just curious about how all this works

 

[BadWolfBrewing]

That is what makes this different from something like a single pass CFC. In that case, you reduce the flow rate to get more cooling. If we were doing some sort of single pass HERMS, where the liquid is drained from one vessel, through a HEX, and back into another vessel with the intent on raising the temperature, you would slow down the flow rate.

In a continuously recirculated mash, you have a finite amount of wort, but an infinite amount of times that same wort can be recirculated. So, instead of optimizing the process to get the most heat exchange per unit of wort, you optimize the process to get the most heat exchange per unit of time.

The way to optimize to get the most heat exchange per unit of wort traveled is with a slow flow rate. In the case of single-pass CFC, you only have a finite amount of volume, and once it has passed through the chiller you can't cool anymore. Time doesn't matter though, so you slow it down to a trickle to maximize the total amount of energy removed from the wort in its single pass through.

The way to optimize to get the most heat exchange per unit of time (which we want) is with a fast flow rate. We have, in a manner of speaking, an infinite amount of wort we can pass through the heat exchanger. We want to optimize the energy transfer per unit of time, because we are battling thermal losses to ambient, which is an energy per time concept as well.

 

[StainlessBrewing]

My pumps, the center inlet chuggers, can really move a lot of liquid if there isn't the flow restriction. The 2-3 GPM I was referring to was how fast you can lauter without causing a stuck sparge. I'm just guessing at the number. At a little over 1 GPM, I still have a pretty loose grain bed. So, with a bigger pump or less restrictive coil, I think I could recirculate faster before having problems.

Only the coil is < 3/8", the ferrules are all plenty big for a homebrewer. Just eyeballing, I'd say about an inch, ID.

A bigger coil with bigger tubing would fill up more of the HLT, that is true. I think there is room for it though. I think somebody ordered a replacement coil from www.stainlessbrewing.com to fit the stout HLT with 50' of 1/2" stainless tubing. Not sure how it turned out though.

Yep, I like mine a lot. The little problems are not deal breakers.

Post 118 bottom picture. https://www.homebrewtalk.com/f41/looking-stainless-coils-325644/index12.html

 

[jesse3474]

If your using a 15.5 gallon keg you need at least 1/2 or 3/4 for coils. Smaller line more pressure bigger line less pressure on your pump,,


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