Thinking Of Building A Herms

[Kytro]

I am thinking of building a HERMS brewing setup. I have someone who can make the equipment, but I need some advice on pitfalls. What should I look out for and what are really nice ideas that have helped make life much easier?

Cheers.

 

[Sammus]

Small volume (5-10L) vessel with as much copper coil as you can fit. Higherly recomended that you can stir the water bath. Assuming you have some kind of electronic temperature controller, have the wort temperature probe right at the heat exchanger outlet, so you dont risk overheating the wort and denaturing enzymes.

That's all that comes to mind right now

 

[Screwtop]

Small volume (5-10L) vessel with as much copper coil as you can fit. Higherly recomended that you can stir the water bath. Assuming you have some kind of electronic temperature controller, have the wort temperature probe right at the heat exchanger outlet, so you dont risk overheating the wort and denaturing enzymes.

That's all that comes to mind right now

+1

Screwy

 

[Thirsty Boy]

Away from the heat exchanger itself - I have had issues with flow rate. When the flow rate drops too far, your temperature control can go out the window. So a well designed false bottom with a good surface area. So you can pull enough wort through to keep the flow rate up, without compacting your grain bed.

Most people are only running off during their sparge... in a HERMS/RIMS you are effectively running off all the time - worth considering when you are thinking about how finely to crush and what mill to buy etc etc.

oh ... and +2 on the above stuff

 

[Kytro]

Thanks, I will keep all this in mind when designing the system.

 

[Vossy1]

Sammus has prety much covered the HE. The smaller the volume of the HE, the faster it will react to temperature fluctuations in the mash. My HE has a 3ltr volume and I insulate all the piping. I use an insulated MT and AFAIC the only 'weak spot' in my system is the non insulated HE pot, I must get round to sorting that at some point.
TB's points are spot on, using a full coverage fb will really help.
Dough in and leave the mash to rest for around 5 mins, then start the recirc pump. If the recirc gets blocked turn the pump off. the grain bed will usually then rise/relax a little, then turn the pump back on.
There's a write up on my HE here
I haven't had to add a 'stirrer' into the HE, as I've had no need for it, though I did consider it for a while when building the HE.
To give you some idea of size, the copper coils are 15cm in diameter and the coil depth is also 15cm. I've got a stainless coil en-route to replace the copper coil, it should arrive shortly.

 

[roger mellie]

To give you some idea of size, the copper coils are 15cm in diameter and the coil depth is also 15cm. I've got a stainless coil en-route to replace the copper coil, it should arrive shortly.

Just as a matter of interest why replace with Stainless? Stainless makes a better insulator than an exchange medium. Stick with copper I reckon.

Just my 2c

RM

 

[sinkas]

SO I can see that you want a small HE to make it chage temp faster, but how big does it need to be abel to effectively chagne the temperature in 40L or recirc wort?

I was going to use a 12L pot, but it sound far too big

 

[TidalPete]

Just as a matter of interest why replace with Stainless? Stainless makes a better insulator than an exchange medium. Stick with copper I reckon.

Just my 2c

RM

Spot on there Rodger. Copper is a much better conducter of heat & that's want you want in a HE.

Vossy1,
Your face looks familiar. Do I know you?

TP

 

[Kytro]

There are a few things I'd like clarified if possible.

I see a number of set-ups out there that use the same size HLT and MLT and Boil Pot, is there any specific reason why? For my MLT I am thinking about adding a false bottom, are there any specific rules about how they should work. I was thinking about a flat false bottom sitting on some metal tabs.

I am assuming a false bottom is usually a metal plate with small perforations or a mesh the grain sits on as the wort is sucked from below.

 

[Sammus]

There are a few things I'd like clarified if possible.

I see a number of set-ups out there that use the same size HLT and MLT and Boil Pot, is there any specific reason why? For my MLT I am thinking about adding a false bottom, are there any specific rules about how they should work. I was thinking about a flat false bottom sitting on some metal tabs.

I am assuming a false bottom is usually a metal plate with small perforations or a mesh the grain sits on as the wort is sucked from below.

Basically. you can buy premade false bottoms that have a curve to them (concave/vex depending how you look at it) ready to plonk on the bottom of a mash tun.

No reason to have all the same size, when you see that its probably because there is an abundance of freely/cheaply available suitable stainless steel vessels that only come in one size h34r:

normally you'd want the kettle to be the biggest, followed by the hlt then MT. I think HLT and MT would normally be a pretty similar size...

 

[Vossy1]

Just as a matter of interest why replace with Stainless? Stainless makes a better insulator than an exchange medium. Stick with copper I reckon

There is a difference between the conductive properties of copper and stainless, and copper is better. One of my own main concerns was the ability to dry the HE between uses, to avoid verdigris formation. Stainless negates that problem, or doing anything fancy to avoid it. I'm also quite concerned about copper in my brew set up due to the acidic nature of wort, and as such I am replacing all the copper and brass fittings, as it's my personal choice to do so.
There's a great piece on the conductivity differences of copper v stainless on one of the US forums...I'll try and find it.

but how big does it need to be abel to effectively chagne the temperature in 40L or recirc wort?

The bigger your HE the slower your heat exchange to wort, as the time taken to heat the HE pool is longer. Small HE's can heat rapidly, transfering the heat to the mash faster. I use a 3ltr HE with 50 ltr mashes on average.

Your face looks familiar. Do I know you?

Hey TP. I noticed another AHB user (Father Jack) uses the same avatar...oops. I've been using the same face in the U.K for a while.
I'll try to find a new one for AHB ;-)

 

[Vossy1]

Here's the info on the conductivity differences between copper and stainless steel which are applicable to HERMS heat exchangers.
The difference is not as big as you would think, and considering HERMS units have a continual heat source, it makes even less difference.

Despite a huge difference in thermal conductivity of 221 vs. 0.12 (Al vs. PP), here is a direct comparison of Cu (k=400) to SS (k=17), .75mm thick (actual SS tubing is thinner, Cu is thicker, so this assumption favors Cu), with a convection heat transfer coefficient for water of 1000 (varies from ~500-~10000, 10000 would be extremely turbulent/fast flowing). (I'll work to more significant digits than are properly allowed, since otherwise any significance from the thermal conductivity is lost!)

First, the formula:

1/U = 1/h1 + dxw/k + 1/h2,

where:
U = overall heat transfer coefficient (heat tranfer per area)
h1, h2 = convection heat transfer coefficient for each fluid
k = thermal conductivity of the wall material
dxw = thickness of the wall material (in meters)

Cu:

1/U = 1/1000 + .00075/400 + 1/1000 = 0.002001875
(note that the factor determined by the wall thermal conductivity is many magnitudes less than the factors determined by the properties of water)
U = 499.53

SS:

1/U = 1/1000 + .00075/17 + 1/1000 = 0.002044118
U=489.21

So, that's about a 2% difference in thermal transfer performance, all else being equal.

Even if you use the extreme for the convection heat transfer coefficient of water (10000, never gonna even get close with a coil chiller in a boil kettle), the resulting difference is minor ( 4954 vs. 4096, or about 18%).

And here's a reference that Polypropylene can be as efficient as metal in a HE

 

[schooey]

I have a 12m SS coil in my HLT for my HERMS. I can maintain my mash temp with having the HLT temp ~4C abovemy required mash temp. That's not much different to what I have seen guys quoting for copper in their systems. I really don't think the difference is big enough to be worried about in a relatively small batch rig that the home brewer would use.

I'm not saying SS is better than copper, just that it works ok in this environment. Like vossy, I wanted to get the copper out of my system....But then again I have a great big copper chill coil in my kettle. Go figure :blink:

i was having a discussion with MHB a couple of weeks ago about this though, and I can't remember the exact science, but apparently it can be beneficial towards clarity as it assists in the formation of the break. Maybe MHB can chime in here if he glances past

 

[roger mellie]

Here's the info on the conductivity differences between copper and stainless steel which are applicable to HERMS heat exchangers.
The difference is not as big as you would think, and considering HERMS units have a continual heat source, it makes even less difference.



And here's a reference that Polypropylene can be as efficient as metal in a HE

Good reply Vossy - now lets apply the real world.

Take a 12" piece of 1/2 inch copper pipe and hold on to one end. Apply some heat to the other end - wait 20 milliseconds - drop the piece of copper pipe - it gets really hot - really really fast.

Repeat with a similar size piece of SS tube - thin or thick - keep applying heat - eventually it will get too hot to hang on to. Might take a minute.

I think we found the metal with the better heat transfer properties.

And applying to our pissy little heat exchanger with our miniscule flows - I think you want the medium with the fastest transfer properties.

And make sure your shiny heat exchanger is passive - some of the nickel products that can leach out of SS are slightly more nasty than a bit of copper oxide.

Cheers

RM

 

[schooey]

Good reply Vossy - now lets apply the real world.

Take a 12" piece of 1/2 inch copper pipe and hold on to one end. Apply some heat to the other end - wait 20 milliseconds - drop the piece of copper pipe - it gets really hot - really really fast.

Repeat with a similar size piece of SS tube - thin or thick - keep applying heat - eventually it will get too hot to hang on to. Might take a minute.

I think we found the metal with the better heat transfer properties.

And applying to our pissy little heat exchanger with our miniscule flows - I think you want the medium with the fastest transfer properties.

In saying that, though, remove the heat source from both, and you can pick the copper again long before you can pick up the stainless. The copper loses heat just as quick as it gains it, where as the stainless has better thermal retention.

I think we are losing sight of the big picture here. Given you have heated water in your HLT to strike temp, and you hit your mash temp the delta temp between where you want it and whats being lost out of your tun isn't going to be that great. So effectively, once you have the coil hot, it stays hot, no matter what it's made out of. Even when doing a mash step from a protein rest of around 50C to a sach rest of 65-67C and then on to mash out and sparge temps of 75C+, I don't find my step times are any longer than what I have read people achieving with copper HERMS systems

Like I said before, SS works well in my system, just as copper works ok in plenty of other peoples.

 

[Sammus]

SS and Cu are both metals, relatively to other non-metal materials, theyre great conductors of yeat. It's like comparing a porche gt2 and lamborghini, sure one might be quicker, theyre both plenty fast though

 

[roger mellie]

In saying that, though, remove the heat source from both, and you can pick the copper again long before you can pick up the stainless. The copper loses heat just as quick as it gains it, where as the stainless has better thermal retention.

I think we are losing sight of the big picture here. Given you have heated water in your HLT to strike temp, and you hit your mash temp the delta temp between where you want it and whats being lost out of your tun isn't going to be that great. So effectively, once you have the coil hot, it stays hot, no matter what it's made out of. Even when doing a mash step from a protein rest of around 50C to a sach rest of 65-67C and then on to mash out and sparge temps of 75C+, I don't find my step times are any longer than what I have read people achieving with copper HERMS systems

Like I said before, SS works well in my system, just as copper works ok in plenty of other peoples.

You dont want thermal retention - you want the energy to transfer.

Never said it wouldnt work - a lot of us have (ahem) converted 50L SS vessels in our breweries - I use mine as a Kettle. If the same vessel was made from copper I would use a shedload less energy to heat the same volume of fluid. Its all about efficiency - some of the energy is transferred using SS - more is transferred using copper - Silver is better still.

I will stop now - I am sounding like Darren.

RM

 

[3G]

Do i need a temp sensor on the outlet of the HE only and use this temperature to turn the HE element on and off. Or do you need a sensor on the outlet to read say 66 and another sensor in the HE water to set the temp at say 68 or 70.

 

[Vossy1]

Good reply Vossy - now lets apply the real world.
Take a 12" piece of 1/2 inch copper pipe and hold on to one end. Apply some heat to the other end - wait 20 milliseconds - drop the piece of copper pipe - it gets really hot - really really fast.
Repeat with a similar size piece of SS tube - thin or thick - keep applying heat - eventually it will get too hot to hang on to. Might take a minute.
I think we found the metal with the better heat transfer properties

Always good to see real science in action

And make sure your shiny heat exchanger is passive - some of the nickel products that can leach out of SS are slightly more nasty than a bit of copper oxide.

It would be silly not to ensure that the copper replacement was less than 304 or 316, which are food grade.
Copper oxide is easily stripped from the surface of copper by wort, but due to acidic nature of wort, it will continue to eat away at the copper also. I'd be more worried about the surface lead on 'older' brass fittings.

I use mine as a Kettle. If the same vessel was made from copper I would use a shedload less energy to heat the same volume of fluid. Its all about efficiency - some of the energy is transferred using SS - more is transferred using copper - Silver is better still.

That would depend on whether you are heating from outside, or inside the kettle. Copper would conduct better with external gas heating, but stainless would insulate better with internal heating....horses for courses I guess ;-)

I think we are losing sight of the big picture here

I agree, sorry.

Do i need a temp sensor on the outlet of the HE only and use this temperature to turn the HE element on and off

Yep. There is/should be (depending on make) an off set parameter in the PID called the PSB which you can use to 'off set' the difference between the HE and MT.