HERMS coil touching side of pot

[Lopsy]

Hello all,

Looking for some specific advice that I haven't found on here before.

I am making the usual 50' SS HEX coil inside a 20 gallon kettle.

After my first pathetic attempt to bend a coil into my pot I ended up with minor kinks and dents. Not too bad, flow shouldn't be too much of a problem. My problem was that I bought the .02 thick tubing and wasn't patient. I used the rigid tube bender (400 series, not the roller one) to no avail. So it was mostly bent by hand and foot. At the end of my struggle I ended up with a coil that slides into the pot by touching the side almost everywhere.

Should this affect heat transfer greatly?

Don't be afraid to over analyze. I want this to be right.

I may just have to buy the .035 thick tubing and do it right by following some suggestions I came across after my first attempt. I'm looking to either be told to not sweat it, or to just buck up and do it right. I'll post some pictures later if you'd like.

P.S. it looks like crap inside the kettle, some parts not strictly decreasing. And because I couldn't make tight radius turns it torques my compression fittings and bulkheads pretty hard.

 

[jbaysurfer]

I wouldn't sweat it tbh. The thicker tubing isn't going to conduct heat as well either so the benefit you'd get by redoing it with the thicker tubing will probably merely offset the small efficiency loss you'll get by touching the sides of the MLT. Ideally, you'd like free water flow all around the surface of every loop of the coil, but again, if you're going from .02 to .035 tubing to do so, I think you're in the diminishing returns category.

I used copper in mine, just for the conductive properties of it vs. steel. Copper is much better heat conductor.

 

[Lopsy]

Deleted

 

[Lopsy]

Refer to next post

 

[Lopsy]

Some coffee, and further refinement:

We have two situations at hand:

1) Heat transfer from HLT water through HEX coil to wort.
2) Heat transfer from wort through HEX coil through pot to air.

For this we will consider a 2 degree difference from the wort in the HEX compared to HLT water. And we assume the inside surface of the pot is the same as the HLT, which makes sense considering the world works in a continuous nature.

1) 16 for thermal conductivity. 0.02" of propagation distance
2) 16 for thermal conductivity. 0.03" of propogation (through tube, then pot)

1) 20.1kW (150F to 148F)
2) 5.6kW (148F to 70F)

Noticeable.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatra.html#c2
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatcond.html#c1

Graham

 

[Ravenshead]

You're making my head hurt:

• Put a coil in your HLT and circulate your mash through it.
• Put your temp probe in the MT.
• Allow your PID to control the temp via it's auto tune function.
• Done.

That all you need.

 

[jbaysurfer]

You're making my head hurt:

• Put a coil in your HLT and circulate your mash through it.
• Put your temp probe in the MT.
• Allow your PID to control the temp via it's auto tune function.
• Done.

That all you need.

Agreed, although I applaud the OPs nerdy-ness, it's about making beer, not reinventing the wheel. The fastest way to increase mash temp in my herms system is to increase the heat in the MLT. The rest is really splitting hairs. Plenty of people have herms systems where the coil touches the kettle wall. And it works with both SS and Copper, so it touching the wall isn't going be a big deal.

Also, while I'm no physicist, it seems to me if you want to do the math right, you need to consider the thermal inertia of the SS MLT which will already be heated to the same temp as the sparge water or thereabouts.

Still Ravenshead's post is the most practical advice.

 

[luhrks]

Still Ravenshead's post is the most practical advice.

+1 You're way overthinking this..

 

[Lopsy]

Sounds good. Thanks for the replies.

 

[kal]

I used copper in mine, just for the conductive properties of it vs. steel. Copper is much better heat conductor.

Correct that cooper conducts heat better than stainless but for our purposes of heat transfer from one moving liquid in the coil to another moving liquid outside, the difference is negligible/not really measurable.

Heat sinks for CPUs are copper but the physics is different... more of a wicking away of heat.

I remember wondering the same a good 4-5 years ago when I was designing my setup and there were long threads about with lots of math from mech and materials engineers (I'm electrical so it made my head hurt). Long story short, the conclusion was that there was no point to choosing a copper HERMS coil over stainless for better heat transfer so I went with stainless.

I use a 50' 1/2" OD HERMS coil and the temp of the wort exiting is equal to the HLT water temp that is used to heat the wort.

Kal

 

[jbaysurfer]

Correct that cooper conducts heat better than stainless but for our purposes of heat transfer from one moving liquid in the coil to another moving liquid outside, the difference is negligible/not really measurable.

Heat sinks for CPUs are copper but the physics is different... more of a wicking away of heat.

I remember wondering the same a good 4-5 years ago when I was designing my setup and there were long threads about with lots of math from mech and materials engineers (I'm electrical so it made my head hurt). Long story short, the conclusion was that there was no point to choosing a copper HERMS coil over stainless for better heat transfer so I went with stainless.

I use a 50' 1/2" OD HERMS coil and the temp of the wort exiting is equal to the HLT water temp that is used to heat the wort.

Kal

Good stuff. I may have chosen copper based on a misguided belief, but nonetheless, it's what I've got now. SS is blingier, but I think I'm finally slowing down on my gear whoring enough to realize that I can make good beer with the stuff I've got on hand. Your setup otoh..I'm almost afraid to look for fear of what it'll cost me.

 

[MX1]

Correct that cooper conducts heat better than stainless but for our purposes of heat transfer from one moving liquid in the coil to another moving liquid outside, the difference is negligible/not really measurable.

Heat sinks for CPUs are copper but the physics is different... more of a wicking away of heat.

I remember wondering the same a good 4-5 years ago when I was designing my setup and there were long threads about with lots of math from mech and materials engineers (I'm electrical so it made my head hurt). Long story short, the conclusion was that there was no point to choosing a copper HERMS coil over stainless for better heat transfer so I went with stainless.

I use a 50' 1/2" OD HERMS coil and the temp of the wort exiting is equal to the HLT water temp that is used to heat the wort.

Kal

Kal is = parts +inspiration and -monies in bank...lol

I too am setting up with a 50foot 1/2 od SS Hex in my 15 gallon pot. Can't wait to brew....

Tim