Amateur HERMS

[Ciderhead]

it settled out 5 above target but like the stc you can calibrate to reflect the difference.

[Ciderhead]

What was the issue?

Sent from my ZX81

As above
" I must of had a loose wire as it was being pushed into project box, its a bit tight in there now alright with the transformer, as all seems to be fine now."

[Will_D]

John, Just check the spec of the SSR: Most of these are now spec'd for 5 volt Arduino type control, (some even down to 3.3 V) You MAY be OK with 12 Volts but just check the specs. May just need a 5V supply!

There ARE some controlers that have an internal 5V supply and so can switch a SSR directly. Most just have relay contacts.

RTFM!

[Ciderhead]

Thanks Will, the input is 3-32V dc so I should be ok

[Hop Bomb]

Very good! Im a few steps behind you. Still building my asparagus pot herms vessel but made a good start last night:



Those lock nuts from ebay are the business. Leak free fitting here with ease. Had to give the pot a tap of a hammer to flatten it so it the element would sit flush but all good so far.
The pot holds 2.5 litres. By the time the coil goes in it'll hold a lot less making it perfect for herms (hopefully)

So does my mash liquor enter the coil at the bottom & exit at the top or vice versa? Thanks.

[Ciderhead]

Nice job, rather that have to drill your pot just run the coil through the lid and put some bends on as you would a wort chiller

I think we had this fluid heat transfer discussion elsewhere on chillers and on chillers it came down
1) It doesn't make any difference
2) the hot wort is at the top so for maximum heat transfer expose the cold water at the top first
3) Your transfer fluid gains more heat transfer as you progress through the coil so transfer from bottom to top

Personally I have always been in favour of No 2, so for herms the mash tun goes straight to the coils on the top first where all the heat is.

My coil is suspended 5-7cm off the bottom away from the base of the burco

Tbh at our level I am not sure it makes a whole hill of beans.

[Hop Bomb]

No 2 makes sense. Cheers.

[JD]

@Hob Bomb

I've been keeping an eye on this thread with a view to doing something like this myself. Initially I thought your idea of the 2.5 heat exchange pot was a neat and tidy idea. Now I'm a little concerned.
Its all to do with heat transfer. I may be way off here so if anyone here is a heating engineer or has a better handle on the physics involved, I'd appreciate their input.

I'm assuming, for the sake of argument, that we're getting 100% efficiency of heat transfer.  In reality, we'll get less.

As I see it, assuming you'll be trying to do a step mash and your mash tun has 15L of liquid in it. To bring this from 55 ^oC to 68^oC, you'll need to put heat into system of at least 195000 (13^oC increase by 15000 ml) calories. This assumes the liquid in the mash tun is plain water as well. An actual mash will require even more heat.   

If you were heating the mash tun directly, the heat would transfer directly from element to liquid as fast at the element could deliver it. I've seen this step take 15 minutes when directly heated so we'll go with that heat transfer rate. This is about 13000 calories per minute. The heat input is down to the surface area of the element mostly so it matter little how much water is being heated, the same heat will be transferred per minute.

Considering your HERMS system, you will be indirectly heating the mash by passing it through the hot water in the 2.5L heat exchanger pot. This means that the heat in the HE pot will be put into the mash tun as fast as the HE coils will allow. For the sake of argument, lets assume that the coil is 100% efficient and that all the heat in the HE pot will be transferred to the mash tun as fast as the heat is put into the HE pot.

So, assuming we can keep it hot enough, the HE pot will have about 6 time less water in it than the mash tun. To increase the mash tun heat by 13000 calories per minute, the heat in the HE pot will need to increase by six times that. Since the liquid volume in the HE pot cannot change, the only way to increase the heat is to increase the temperature by 6 times but since we are heating water, we hit a hard limit of 100^oC. This means that for our 13^oC rise in the mash tun, we need to see a 78^oC rise in the HE but we can only manage a 45^oC.

The inevitable consequence is that we cannot get the mash tun up to temperature in the same time as it would take were we directly heating the mash. We need to extend the time. In the above calculations, we would need to extend the time by a factor of (78-45)/45 or 73%. What would have worked using direct heating and took 15 minutes will now take 26 minutes. In that 26 minutes the HE pot will need to remain at 100^oC. This is boiling temperature for water. Your pot will boil dry before the step completes.

I contend you need a bigger HE pot.

/J

[Hop Bomb]

Im not trying to heat all the mash liquor at once though. Im using a pump to recirc the mash liquor through the HE. With a smaller volume herms pot it reacts much quicker when you want to increase temp. Flow rate on my current pump is 8 litres p/m but Il be going a little slower than that as I dont want to turn my grain bed to concrete. In a 15 min step my entire mash liquor will have passed through the herms coil a shit load (to use a technical term ) & il hopefully be able to hit my targets & hold it there. Im pretty sure my 2.5 litre pot will be fine as lads on here & other forums are doing fine with 1.7 litre kettles as herms. If Im not though il be the first to post about it. 

[barkar]

Yeah with reduced flow rate and the volume of water in your coil  you should see pretty quick temp increases . A pid is self learning so it shouldnt overshoot - it may on initial auto tuning stage but after that should be fine. I set pump usually to 8- 10v of power (dont know how many l / min but it is a slight bit more than a trickle and considerably less than full bore!) Similarly you ar adjusting the power to the element based on the temp of the wort leaving the herms / entering the tun. Some might say it would be better checking temp in the tun as an adjustment in the herms but temp may not be equally spread across the tun.   

[Ciderhead]

JD complicated but very valid points, my thermocouple is in the middle of the mash grain bed and because I spread flow of wort uniformly across the top of my grains I know thats my tun temp.

If I start at 60 with a target of 68 and 4-5kgs of grain and about 13l of water with a solar pump I can circulate 7L per minute, I am getting temp rise by between a degree to 1.5 per minute, more that this with a stronger pump and potentially you compact the grain to a concrete block and less that this and as you point out it takes an age, so about 6 mins to do the above.

In the states they were big fans or large coils in their HLT, but there is no quick response to immediate requirement for temp increase if you have to heat 30L of water, even on my HLT with 2 elements its takes over half an hour to boil.

When I fly sparge even though my temps are good from HLT I still pass through the herms, to wash out and also ensure temp

I guess the reason HB and I are doing it is it gives much better consistent control of mash temp with minimal overshoot perhaps a degree on first heat, but with the flow its only overshot for a minute, so unlike direct heating with gas or underback where you can blast it but tricky to hit and hold your numbers.


I was reading last year about thermal shock and this process avoids that obviously.

To me one of the big things is the quality of the crud from the hot break, there isn't any!, whereas in the past I used to find myself scooping it off.

Controlling and maintaining is a doddle as well and because of the constant throughput. 

[Ciderhead]

HB I should also point out here I boil or pass through a volume of boiling water through pump and herms at start to give everything a good swill out and then I backfill hlt to bring water down to required strike temp.

[DEMPSEY]

My HERMS pot uses a 2.2Kw element and heats a 10 Litre pot. What I found was instead of heating the HLT and transferring hot liquer to the Mash Tun to blend with the grain I can instead put the required amount of liquor into the Mash Tun and use the HERMS pot to heat it up. this free's up the HLT for sparge liquor.

[Ciderhead]

Dempsey, what sort of transfer rate are you getting?

[JD]

I'm sticking to my guns about my concerns over the pot size. Ciderhead and Dempsey use bigger pots. Ciderhead is getting up to 1.5 degrees rise per minute and he's using a 10l HE pot. The mash recirculating many times just means the heat in the HE pot get to the mash quickly. It does not mean that the HE pot has any more heat capacity.
The heat going into the mash tun has to come from the water in the HE pot. The pipes and pumps used, no matter how good or bad they are, will only interfere with that transfer. They cannot improve on it. It's thermodynamics and there are no truer laws in all physics.

If, as HB is doing, a 15l mash tun is to be temperature controlled by a 2.5l HE pot, then if the mash tun is to be raised by 1 degree, the HE pot, assuming the element is switched off, must drop by 6 degrees. The element in there so the HE pot can replenish that lost heat. The pace at which the mash tun can be heated is the rate at which the HE pot can be replenished divided by six.

If all the system is to be used for is single infusion, then the system will work fine. As a means to stabilise the mash temperature, the pot size is fine. My concerns are if the system is to be used for step mashing. Going from a protein rest temp of 50 to a sacharrification temp of 67 will cause the HE pot to boil dry, I fear, and the 67 will not be reached.

Hopefully I'm spouting rubbish. I'm going to be seriously interested in the performance of HB's heat exchanger. There'll be no one happier when his HERMS works perfectly. I'm just a wee bit worried it won't.

/JD