Technical Mash Tun Question involving thermodynamics.

[idzy]

Hi fellas,

I am brand new here and this is my frist post so please excuse me for any mistakes I do. Anyway I will start by describing my new electric mash tun I have created. It is a 50L stockpot with a 2.2 kW heating element inserted into the side with a false bottom about 20mm above the heating element. The stockpot is 40 mm in diameter, unfortunately I was not given the height in the spec but I could measure it if needed. I have got an STC 1000 wired up to control the heating element to keep the mash tun temperature at an accurate temperature setting. My question is, will the heat transfer rate from the heating element to the water be fast enough to be able to assume that the grain and water are the same temperature at every point inside the mash tun? and if so does that mean I can put my temp sensor anywhere in the mash tun and effectively keep an accurate temperature? I have done some basic thermodynamics in 1st year Physics but I think this is beyond me.

Thanks in advance for any replies!

Unlikely. You need recirculation or agitation through stirring the mash. The other problem could be scorching during mash steps, which is experienced in a RIMS system with recirculation. The other concern is the use of an STC-1000 over something like a PID with SSR (solid state relay). With a solid state relay you can turn the element up and down by percentage. With no recirculation and an element at 100% it will be quite problematic.

I would be investigating either a RIMS or HERMS system if you are looking to heat your mash with electricity. Most brewers on here use HERMS and target to keep within 1c across the entire mash for a given mash step.

A way to test your system (if already built) would be two probes, one near the element and another near the top of the mash.

 

[Liam_snorkel]

I have essentially the same setup.
Temp probe placed between the element and the pump inlet.
My pump is a little brown pump. With it on full-whack, it takes a while to 'clear' the wort from below the FB and start sucking 'unheated' - The temperature at this location fluctuates as much as 5-10 deg over target during these periods. I use a thermapen to check the mash temp and it's within 0.1 deg of target while this is happening.

 

[CyberAle]

Tips for recirculating.

Mash in and let rest no recircing for a few minutes

To start no more than 1/3 full flow for 10 minutes to 'set the grain bed'

Gradually increase to full flow.

Note flow is controlled
with a ball valve, the ball valve should be located on the outlet of the pump in all cases.

Cool, I have a recirculating pump now that works well except i have no ball valve. Just wondering what the initial no circulation does? I actually put the mash in at around 50 degrees so I don't scorch any of he grains and then bring it up to about 66 degrees.

 

[Lyrebird_Cycles]

Just wondering what the initial no circulation does?

The idea is to allow the bed to settle a bit before you start pulling. Pulling early will tend to increase the concentration of barley endosperm* at the bottom of the mash which can lead to the creation of a relatively impermeable bottom layer. If you allow the mash to settle itself and then pull very gently at first you should get a better mix of husk and other particles in the bottom layer.


The best way to manage this is by differential pressure; ideally you want to be under 0.3 kPa for the forerunnings and then to keep the DP across the bed as low and as even as possible through the run, preferably under 1 kPa over the entire area. I keep my lauter running at about 0.6 kPa until I'm well into the sparge.




* The endosperm has relatively high beta glucan level, the beta glucan absorbs water and swells to create a mucilaginous matrix which is very effective at blocking the bed.

 

[malt junkie]

Also The no circulation at mash in allows time for the grain to absorb liquid and expand.

 

[Lyrebird_Cycles]

Ah yes, most of my experience is with systems with separate mash and lauter tuns, I hadn't considered that one.