only recently, about one month ago, I finished my HERMS setup and did my first batches with it. I was surprised how my feeling for thermodynamics and heat exchange were actually wrong. My setup consists of 3 vessels and two pumps. Mash tun capacity is 50l and I am aking batches of about 45l. I have temperature sensors in many places, mash tun, HLT, HERMS out, the inlet of the mash tun from the HERMS, sparging inlet and so on. In this post, I would like to share my experiences and also to ask some questions which I believe are interesting for other brewers:
First, I couldn’t believe that heat exchange through the HERMS coil (I use 3-way version) works in that way that if I am stepping to 70 degrees, my how water is at about 76-77 degrees and that there is 6-7 degrees temperature difference of the wort coming out of the HEMS coil and the how water around the coil. I thought there should be plenty of time and area to actually exchange the heat. I am not disappointed, jut excited about my new discovery .
If I set my PID to let’s say 68 degrees, the hot wort from HERMS coil entering the mash tun will indeed always be 68 degrees, but the mash itself is always lower. This was the biggest surprise to me because the mash doesn’t reach the set point in some acceptable time frame. My pump is set almost at the maximum, which means that in only 3-4 minutes the whole liquid volume is pushed through the coil, so I was expecting after 10 minutes to have the main mash at the set temperature. Do you also experience this? Do you use a sensor inside the mash for controlling your PID or the output of the HEMRS coil? I use the output of the coil. If so, how is possible that the grans have such thermal capacity? And finally, if I am pushing the wort through the coil where it reaches the desired temperature, that could also mean that the mash conversion is actually happening there. So, what should be the reference point in this case?
Brewing German type wheat beer was really stressful and basically impossible due to the stuck mash. I did all rests, at 38, 45, 51, 55, etc … but at some point especially about 60 degrees the mash bed becomes hard and impenetrable.
What do you think?