I'd expect that a PID controller should be able to compensate for the overshoot caused by the lag time. The temperature response through a thin-walled copper pipe is going to be very fast but I don't think the response time through a SS bolt is going to be a whole lot less. 'Yes', it will be a little slower but I don't think it will be noticeable.
Copper is 28 times more conductive than stainless steel that is a fact. Length and thickness effect this of course. But that is significant especially when 1 to 1.5*C of temp difference can wreck havoc on a beer.
I agree a good SSR PID would be able to compensate but why bother having to do all that work for a naff solution?
Besides that drilling a hole in a bolt accurately isn't a job for the average Joe, no? Certainly no a hand drill job IMO. Ok assuming that we have a drill press the best you can do is a 1mm side wall which I am assuming a M8 bolt with a 6mm drill bit. Going to any bigger hole I would suggest you be getting too close to the thread cut.
Anyways here is a little tid bit from Engineering Toolbox to clarify.
Heat conductivity:
A figure of merit for copper is 231
A figure of merit for stainless steel is 8.1
A figure of merit for steel (mild) is 32
A figure of merit for aluminum is 136.
The units are BTU / H * ft * Degrees F.
For a given length of time copper will conduct almost twice as much heat as aluminum and 28 times as much as stainless steel (but only about 7 times as much as regular steel). This is why there are copper bottomed stainless steel pots.
I've got a copper pickup tube in my kettle and haven't noticed any corrosion. Caustic solution is another matter... There are lots of German breweries running copper kettles without too many corrosion issues. I also heard on a Brew Strong episode with Dr Charles Bamforth that a little copper in a system is a good thing as it helps stop some weirdo reaction from occurring.
I could see galvanic corrosion possibly being an issue though.
just my $0.02 worth.
garyd
So you haven't notice the copper pick up tube go from a dull coppery colour before the boil to brighter coppery colour afterwards then? When I had a copper manifold in the MLT I saw this happen every brew day. And yes it is galvanic, usually. Beer is corrosive and it is acidic, no? Obviously a good oxide layer will help to prevent this from happening but maybe take a closer look next you brew?
Yes a little copper is apparently great for yeast health as well. A lot of the big breweries will use a sacrificial copper annode in there systems for this reason but as well as for taste apparently? I have never been employed by a big brewery only done the tours but I have been told by someone that is in the know of this situation, which I have taken on face value.
As for the Germans and copper breweries I wouldn't think that they are as maintenance free as you suggest but I have never worked in one or around one so I can't comment any further. I have however noticed a lot of the modern commercial offerings that I have seen researching on the net are stainless steel lined with a copper sheath to keep up the illusion of grander days at a guess? Maybe there something in that?
Anyway obviously I can't be taken too seriously so here is an except from BYO's website that will help to clarify the situation:
"Copper
Copper has the highest heat conductivity, is easy to form and was traditionally used for making the brewing kettles or coppers. Copper can be readily soldered, brazed and welded with the proper equipment. Soldering and brazing should be more than adequate for most brewery uses.
Copper is relatively inert to both wort and beer. With regular use, it will build up a stable oxide layer (dull copper color) that will protect it from any further interaction with the wort. Only minimal cleaning to remove surface grime, hop bits and wort protein is necessary. There is no need to clean copper shiny-bright after every use or before contact with your wort. It is better if the copper is allowed to form a dull copper finish with use.
However, you need to be aware that copper can develop a toxic blue-green oxide called verdigris. Verdigris includes several chemical compounds cupric acetate, copper sulfate, cupric chloride, etc. and these blue-green compounds should not be allowed to contact your beer or any other food item because they are readily soluble in weakly acidic solutions (like beer), and can lead to copper poisoning (i.e., nausea, vomiting). To clean heavy oxidation (black) and verdigris, use vinegar or oxalic acid-based cleansers like Revereware Copper and Stainless Steel cleanser.
For regular cleaning of copper and brass, unscented dish detergent or sodium percarbonate-based cleaners are preferred. Cleaning and sanitizing copper wort chillers with bleach solutions is not recommended. Oxidizers like bleach and hydrogen peroxide quickly cause copper and brass to blacken; these oxides do not protect the surface from further corrosion, and are quickly dissolved by the acidic wort. Copper and other trace metals are beneficial nutrients for yeast, but the amounts that are dissolved from non-passive oxides can be detrimental to
the batch.
Copper counterflow wort chillers should not be stored full of sanitizer or water. Any biological deposits can lead to corrosion in both water or sanitizer. Copper should be rinsed thoroughly with clean water and allowed to drain
before storage."
old corny keg dip tube works well for these, stainless, perfect size diameter wise, just cut it to length and fold the end over neatly.
+1 Great solution!
Chap Chap
