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
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
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.
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.Just as a matter of interest why replace with Stainless? Stainless makes a better insulator than an exchange medium. Stick with copper I reckon
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.but how big does it need to be abel to effectively chagne the temperature in 40L or recirc wort?
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.Your face looks familiar. Do I know you?
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%).
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.
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.
Always good to see real science in actionGood 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
It would be silly not to ensure that the copper replacement was less than 304 or 316, which are food grade.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.
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 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 agree, sorry.I think we are losing sight of the big picture here
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.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
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