Originally Posted by theonetrueruss
I am thinking all this is over-complicating the issue. The temp of the wort coming out of the herms tube is what is important and if you are regulating your heat source via PID/controller off of that the control should not care about the heat stratification and it just wont matter as long as it can get the wort coming out at a consistent temperature.
I am running my eHERMs without any circulation of the HLT water and only using a simple temp controller and the temp coming out of the coil stays within 1 degree of my set point.
Please tell me where I am wrong?
Some things to think about. Do we even know how much of a temperature difference is going on with any given system design? Is it 20 degrees? Won't the copper or stainless coil also help carry the heat through the HLT?
Enough of a temperature difference could theoretically change the temperature of the wort enough at a certain point in the coil that the enzymes don't perform as expected. IMO uneducated mind, the likelihood of this happening is very slim. I imagine that once a wort reaches a stable temps, the temperature differential is not enough to be concerned with.
A larger diameter and shorter coil would obviously have less stratification going on than one which is narrow and tall. Therefore there may be more of an issue with the latter design.
That all said, there are several methods used to prevent stratification and most of them are very cheap and easy to use. So until there is sufficient data to the contrary, it would be wise to use one of those methods to prevent any problems.
I personally was intending to use a small food grade recirc pump mounted right on the side of the HLT. A car's window wiper motor would be great for operating a stirrer as well. They can be had for $15 or so at junk yards and are ready to run with a small 12V supply.