Amateur HERMS

[Hop Bomb]

Your logic is based on science. I cant really argue with that - it wasnt my best subject in school. Im basing my herms on other peoples designs already in use (particularly the kettle herms) I wanted to build something of similar size but with a nicer finish. Barkar uses a currys 1.7 ltr kettle as a herms with no issues (hopefully he'll chime in on his attempts (if any) at step mashes). I hope you are spouting rubbish too. If you arent Il only be out 20 quid as all the hardware can be swapped over to a larger pot.

[Ciderhead]

Luvin this discussion
Just went and measured vol in my burco and as copper displaces, I have just 5L of water to cover over the top of the coil, I have a makey up plastic lid but didn't notice a huge boiloff last couple of times.
Heres the crunch number for you JD, I have just over 5M of coiled copper in there so I guess I am getting optimal heat transfer?  I have 10MM so thats over 1.5L right?

[Buri]

@ JD. There is a mistake in your logic I believe.

Look at it from the other side. If a pump can transfer 11 L per minute. so 22L are pushed every 2.min. In other words I can put entire mash through HERMES every 2 min.

There are three factors.
1. coil needs to be long enough to heat mash to a target temperature.
2. HERMES heating element needs to sustain heat output of the coil.
3. flow rate.

So if I have heating element of 4.5 kw It is possible to make coil with similar heat transfer properties.
Look at it as a heating element inside a mashtun that has very thick walls. you just need a large surface to transfer the heat.

[barkar]

I generally get brainfreeze re anything regarding science  -  i just followed what i had read form other forums which suggest the smaller the pot  the better the change in temp , as you will probably recirculate the mash water numerous times through the herms you will/should raise the temp at every loop etc.  I have 2.2kw element to heat 1.2 litres at every crossing. The larger the water size the less kw you have per litre 

In relation to step mashes i haven't really had to need to do that , generally don't brew pilsners or lagers.

What i have found is that where i have missed mash temp for one reason or another i have managed to raise the temp comfortably to desired temp. One instance i didn't heat the tun before doughing in the tun -  mash temp was 55/6 c - i wanted 66-68 - recirculated and in approx 5 - 10 minutes it was where i wanted -  wasn't ideal nor planned but did constitute a step mash. 
I can have a play on friday to see will it raise temp sufficiently by 15 - 20'c. from 40 to 60 odd to 70 etc. in the interests of science etc.

 

[johnrm]

My 2c...
Not only are you heating the mash, you are cooling the Herms Pot.
This means that the Pot does not boil for the duration of the Heat exchange as the intermediate liquid is being cooled as heat is being transferred.
As it is not boiling, the pot does not boil-dry.

[JD]

Barkar's real life numbers are the most telling. They trump all the philosophising I was doing earlier. I'll concede in the face of hard facts.

Thinking about it further, Johnrm has hit on the flaw in my argument: I failed to include the simultaneous cooling of the HE pot. It is this that will prevent any boil off.

@ Ciderhead
So you have 5M of coil and its got a 10mm diameter and your question is 'what's the volume of liquid displaced by the pipe'? Not as easy to figure as it might first appear. The pipe, when straight, has a capacity in millilitres of L x R² x PI. L is  pipe length in centimeters = 500,  R is the pipe radius = 0.5  and PI=3.14159. This amounts to 393ml. If your question was about how much liquid is inside the pipe, the wall thickness needs to be subtracted from the radius and the above equation recalculated.

With the pipe coiled into a helix the equation is more complicated. http://en.wikipedia.org/wiki/Spring_%28mathematics%29. Note that this article acknowledges that its formulas doesn't take into account the distortion of the pipe that occurs when it's bent into a helix.

[Ciderhead]

I think I'll pour it into a bucket  and measure it

[Hop Bomb]

Classic practice v theory here. Some tests would be great Barkar. Seeing as its all about surface area could I use a plate chiller as a HE? Pump + recirc x temp water through one side & pump mash wort through the other? My plate chillers surface area is 0.36 m sq.

[Ciderhead]

Classic practice v theory here. Some tests would be great Barkar. Seeing as its all about surface area could I use a plate chiller as a HE? Pump + recirc x temp water through one side & pump mash wort through the other? My plate chillers surface area is 0.36 m sq.

are there not issues around excess proteins and particulate sticking in your chiller that normally are on the bottom of your boiler?
i know nothing about plate chillers :

[DEMPSEY]

I will do a practical test later on. I will put 20 Litres in the mash tun check its temp and use the HERMS pot only to raise its temp.

[johnrm]

This should be a good test, although the thermodynamics of Water vs Sweet Mash will be slightly different.

[DEMPSEY]

OK ran the test. Put 20 Litres of water into Mash Tun
HERMS temp was 16.3 C 
Mash Tun temp was 16.1 C.
Switched on the Herms Pump and the Herms Heating element at 18.55pm. Target temp set at 50.0 C

@ 19.17 pm
HERMS temp 35.7 C
Mash Tun temp 34.0 C

@ 19.32 pm
HERMS temp 50.0 C
Mash Tun temp 48.9 C
HERMS heating element switched off at the 50.0C HERMS pump continued to recycle water.

@ 19.33 pm
HERMS temp 50.6 C
Mash Tun temp 50.0 C

Despite the HERMS element switched off the temp still continued to rise

@ 19.37 pm
HERMS temp 51.4 C
Mash Tun temp 52.2 C

@ 19.44 pm
HERMS temp 51.3 C
Mash Tun temp 52.1 C

Temp had peaked and was now falling back. I found that with grain in the Mash Tun this was better controlled.

[barkar]

I done something similar


I tried same test 21-2 litres in closed system ie tun and recirculating coil (approx a litre in pipes) ,

Ambient temp was bang on same as Brians 16.3  both herms water tun and set at this 

I dialled in 41 ish into herms pid

I put a thermometer in the furthest part of the tun from the return and used that as evidence of the minimal temperature in the tun  - while both probes were equal at the start - there was approx 8 degrees differential between it and the Herms probe once the element started 

Measured in 10 degree increases in tun thermometer rather than probe out of herms coil


16.4 - 26.4   10c in tun   8.5 minutes

26.4 - 36.4 again 17 minutes(8.5 minutes in step)

41c ish met in tun at 20 minutes

Turned off herms once temp reach let water recirculate until the temperature between the 2 equalised

Set pid to 68 again measured in 10c increases in the temp probe in the tun  - reached 61 bang on 17min ie 20c  jump

As the pid was set  to 68  it took another 10 minutes to equalise, i am sure if it was set higher it would have come about quicker as the pid was only pulsing the heat on and off for the majority of this)


Not sure which is more efficient


I can t really explain the differential in temp between the 2 probes as thermal loss as a result of
1.  Size of tun - 80 liotres
2. 1 Metre of return from exiting herms back to tun
3  Lag for equalisation (?) of water temp across the tun -  probe was set furthest away from return   
4. Water in coil at any given time was 250 ml
5. 2 different probes 1 stc v pt100 reaction speed of temp change maybe quicker than stc probe

[Hop Bomb]

Super work lads. Thanks!

[JD]

Excellent results. My worries are completely unfounded. That last 17 minute step of Barkar's experiment is the very case I was concerned about.
/J