# HERM IT coil to hold fermentation temp - Small build



## Khellendros13 (3/10/15)

So I am looking at a 7gallon Chronical and the FTSS kit.

Problem is, the controller it comes with only runs the pump. I ideally I would like to have a heat pad or belt for those colder nights.

I planned to run the cold water from my keezer, and want to see if it can achieve cold crash temps.

Last night and today I got to rigging up a test using a coopers FV and my HERM IT coil (smaller then the FTSS coil I should note). I bought a pond pump and sat it in a bucket in my keezer.

So far, results are not fantastic in a 28c garage, though I have not let the pump water get to 2c yet, so a test in the morning should prove better.
With 19.5c water in the fv it only manages 18.3c

I do plan to get the FTSS coil and jacket if this ends up working, and install the coil in the side so I can keep the domed list for pressurized keg transfers.

Photos below, I'll post back with results once the pump water has cooled to 2c and see how quickly I can get it to 16c, and then 5c (not quite cold crash but I think even this will push it).


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## Moad (3/10/15)

Some insulation might help?


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## Tex N Oz (3/10/15)

What is the volume of water in the reservoir (keezer)?


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## Tex N Oz (4/10/15)

Bear with me while I put my nerd pants on but it appears that what you are trying to do is not possible with the equipment you are using. I'll try to explain it below.
Let's say you have your volume of water in the keezer down to 2°C and the water in the fermenter is 28°C.
When you first turn on your pump, you will see the temperature (T) of the fermenter quickly fall to the temperature as outlined in the equation below. 

Assuming the volume of water you are trying to cool is 26.5 litres and the volume of water that you are using to cool with is 5 litres (as I assume by your pictures).

the sum of the heat lost from one to the heat gained by the other = 0 So ΣQ1+Q2 = 0

Q1 = the heat gained by the reservoir in your keezer Q2 = the heat lost by your fermenter.

The equation is as follow as there are no phase changes (melting ice) involved.
m=mass
c=specific heat
T=temperature

m1c1ΔT1 = m2c2ΔT2

(5000)(4.186)(T-2) = (26500)(4.186)(28-T)
20930(T-2) = 110929(28-T)
20930(T)-41860 = 3106012 - 110929(T)
131859T= 3147872
T = 23.87°C

At this point, both the water in the keezer and the water in the fermenter are equalised at 23.87°C. Any further cooling of your fermenter will require the heat lost in the keezer reservoir to be greater than the heat gained by your fermenter from the ambient. Eventually you will find an equilibrium there as well as the heat exchange rates "stall" and become equal with each other at a given temperature.
I seriously doubt you will see anything close to 5°C without some modifications to your system. 
Firstly, change the plastic bucket for a metal bucket as metal will exchange heat at a much faster rate. Second, insulate the fv the best you can. Actually, insulate anything that's outside of the keezer.
I'd also put a small computer fan in the bottom of the keezer blowing air over the metal bucket. I'm not fully convinced you will get to your 5°C with a 2°C setpoint of your keezer as that's only a ΔT of 3°K
Your fv will need to be insulated at least as well as your keezer and the capacity of your compressor must also handle the load. You might find the product in your keezer gains in temperature before the system stabilises. 

Edit: I should also note that the coil you are using is more than enough for the volume of your fv. Upgrading will only be a waste of $$ as it's definitely not the weak link in this system.


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## Khellendros13 (4/10/15)

Tex N Oz said:


> Bear with me while I put my nerd pants on but it appears that what you are trying to do is not possible with the equipment you are using. I'll try to explain it below.
> Let's say you have your volume of water in the keezer down to 2°C and the water in the fermenter is 28°C.
> When you first turn on your pump, you will see the temperature (T) of the fermenter quickly fall to the temperature as outlined in the equation below.
> 
> ...


Thanks for the detailed info, even if I struggle to understand the equation.

You are right, the water in the keezer is too low volume for heavy duty cooling, I might try a keg when I have time to swap it out. Volume+better heat exchange.

I didn't bother to insulate as I don't have anything ideal around. I would use the jacket for the Chronical 7 though. The coil in the FV currently is my HERMs coil, so either way I would need a new coil...and the brewtech coil has more sanitary fittings welded to it as well.

This morning the FV temp was 20.5c, after almost 90 mins it is now 16.7c...looks like that is the limit of 1 cycle with the current water volume in the keezer. I'll get a bit more scientific Monday hopefully and try with a full keg.


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## Tex N Oz (4/10/15)

Khellendros13 said:


> Thanks for the detailed info, even if I struggle to understand the equation.
> 
> You are right, the water in the keezer is too low volume for heavy duty cooling, I might try a keg when I have time to swap it out. Volume+better heat exchange.
> 
> ...


I think with a full keg of water you would have much much better results. Here are a few numbers.

(20000)(4.186)(T-2) = (26500)(4.186)(28-T)
83720(T-2) = 110929(28-T)
83720(T)-167440 = 3106012 - 110929(T)
194649T= 3273452
T = 16.81°C
equilibrium at 16.81°C and then with much higher exchange rates of the surface area of a stainless keg you might get to where you want to be fairly quickly. Didn't think about this last night as I had put a few (dozen) brews down at the food show.. Paying for it this morning. 

Edit: Freakin hang-over from the deepest darkest spot in hell this morning. Anyway, you're welcome. Happy to help a fellow out. The equation though it looks daunting is fairly straight forward but very good to know when dealing with thermodynamics. If you could manage to build an ice bank out of your system it would be even better. The latent heat of ice is around 333.55 joules of energy as opposed to water at 4.186 joules (kg). I might travel this road myself to avoid huge fridges for everything.


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## cke11y (8/10/15)

Great experiment!

I can't help with maths but see this thread: http://aussiehomebrewer.com/topic/86800-a-glycol-chiller-using-bits-i-have/

I did something similar. Having a copper coil in permanent ice on my return side reduces my reservoir temp increases significantly. My setup can hold lager ferment temps on a hot day (my brew space is a cool room though) as proven last weekend. It definitely cannot cold crash though! Bummer! Maybe with glycol I could? Dunno?


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## sp0rk (8/10/15)

Whatever happened to a fermenting fridge...


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## TheWiggman (8/10/15)

There's a minor conceptual flaw in lines with what's already been said. Your maths is correct Tex N Oz but only accounts for two vessels in a closed system, in reality there is a keezer running which will continue to transfer heat after the initial exchange has occurred.
For the reservoir in the keezer you effectively have a volume of water in - let's say - 4°C ambient. The fermenter will be sitting in an ambient temp of 28°C. At _best_ you aren't going to achieve a result better than halfway between, which is 16°C. You'll have one tub sitting in the keezer radiating heat at 16°C, and another tub sitting on the shelf sucking in heat at 16°C (notwithstanding vessel sizes, there will be minor differences in reality). The main limiting factor for cooling is going to be the ability of the cold to transfer* into the HEx in the keezer. The two ways to improve this would be -

Insulate everything outside the keezer where you don't want heat transferred
Improve convection around keezer HEx
Pump/circulate water in vessel
Remove vessel altogether and set up fan blowing across coil

I personally think the last bullet point would be the best. This turns it into a radiator, which is the #1 heat transfer method worldwide. Used in cars, mobile equipment, air conditioners, transformers, the keezer... And insulate.

* Yes, I know this isn't the way heat travels but the concept remains the same


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## Tex N Oz (8/10/15)

TheWiggman said:


> There's a minor conceptual flaw in lines with what's already been said. Your maths is correct Tex N Oz but only accounts for two vessels in a closed system, in reality there is a keezer running which will continue to transfer heat after the initial exchange has occurred.


I said "Any further cooling of your fermenter will require the heat lost in the keezer reservoir to be greater than the heat gained by your fermenter from the ambient."
How does this relate to a closed system?




TheWiggman said:


> For the reservoir in the keezer you effectively have a volume of water in - let's say - 4°C ambient. The fermenter will be sitting in an ambient temp of 28°C. At _best_ you aren't going to achieve a result better than halfway between, which is 16°C. You'll have one tub sitting in the keezer radiating heat at 16°C, and another tub sitting on the shelf sucking in heat at 16°C (notwithstanding vessel sizes, there will be minor differences in reality).


Of course I can. If the volume of -4°C water is greater than the 28°C water, I will equalize at a temperature lower than half-way and those differences can be much greater than minor.
Going back to ΣQ1+Q2 = 0 with Q1 and Q2 being m1c1ΔT1 and m2c2ΔT2
It's the basic heat equalisation calculation barring latent heat or other states of the mass.



TheWiggman said:


> The main limiting factor for cooling is going to be the ability of the cold to transfer* into the HEx in the keezer. The two ways to improve this would be -
> 
> Insulate everything outside the keezer where you don't want heat transferred
> Improve convection around keezer HEx
> ...


If you go with this route, you'll completely lose your heat storage reserve and it will take much longer for initial temperature reduction of your product, not to mention the problems associated with a small closed loop recirc system..


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## TheWiggman (8/10/15)

Holy quotes! I will say I missed one thing, I thought there was a coil in the bucket inside the keezer. There isn't, it's only a pump, so replace



TheWiggman said:


> Remove vessel altogether and set up fan blowing across coil


...with...
'Set up a fan blowing across the bucket'

It wasn't an attack at your credibility, there is an unknown you aren't considering which means the heat equation isn't the be-all and end-all. I didn't say negative 4°C in the keezer, I said 4°C. The heat equation you've stated is for a closed system because there is no Q input or output. There is no consideration there for convections rates and coefficients. 

What it says is (and yes you've already said this, not being patronising) -

Body 1 has a certain amount of heat energy which is transferred to body 2
Body 2 has a certain amount of heat energy which is transferred to body 1
The amount that transfers between each is the same, and the temperature settles to equilibrium.
This say nothing of the continual heat transfer between the fermenter and the ambient air, and between the cooling water and the fridge air.
What happens if the keezer is turned on and remains on?
What happens if the heat transfer convection coefficient is improved to the surroundings in the freezer?
What happens if we insulate the fermenter?

We want to reduce the rate of transfer between the fermenter and surroundings (28°C) and increase the rate of transfer between the cooling water and the keezer (4°C).

Reduce transfer between fermenter and surroundings - insulate.
Increase transfer between cooling water and keezer air - a radiator with 4°C air blowing past it (in the case a coil with fluid pumping through it) will have far better heat transfer than a bucket/keg full of water sitting in a still environment. The limiting factor is the heat transfer convection coefficient between the cooling water and the thing cooling it, the cold air in the freezer.

There are better methods after the initial chilling has taken place than placing the bucket in a keezer, keeps fluids (air and liquid) moving is one of them.


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## osprey brewday (9/10/15)

try and find an old work shop water cooler (bubbler type thing) and use a recirculating closed loop. insulate all hoses and fermenter try gum tree ect for water cooler


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## osprey brewday (9/10/15)

osprey brewday said:


> try and find an old work shop water cooler (bubbler type thing) and use a recirculating closed loop. insulate all hoses and fermenter try gum tree ect for water cooler




this is what i plan to use to chill a conical if i ever get one thinking of using solar swimming pool tube mat to wrap around or a copper tube wrap work that bit out when need be.
Aquarium chillers are another option


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## Tex N Oz (10/10/15)

It's all good mate. I never felt you were attacking my credibility and I'm always up for sharing of ideas and information. 
Understand, I'm not one to debate for the sake of being "right for my ego" but instead for being "correct for the science". While I, like everyone else, hate being wrong, I will always step up when it's obvious that I'm so. On the flip-side, I'll always point out something that's incorrect but it's not intended personal either.
With all of that said, I've "marked" your quote below in blue to highlight my response.



TheWiggman said:


> Holy quotes! I will say I missed one thing, I thought there was a coil in the bucket inside the keezer. There isn't, it's only a pump, so replace
> 
> 
> ...with...
> ...


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## Kingmaa (10/10/15)

I'd be looking at an aquarium chiller. Refridgerated units that cool fluid as it is pumped through. Most would be able to chill 25 litres to freezing, even the cheap ones are rated for up to 20 degrees pull down on 500 litres of water


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## Khellendros13 (11/10/15)

This certainly took off like a big stout!

Appreciate all the maths and ideas here, been short on time with work and my mum in hospital for a hip replacement.

The end result right now, is a Coopers Recipe pack English Bitter (gathering dust since Feb) fermenting away with a starter of Nottingham (was 3 months expired). Pitched at 18c, been sitting at 20.5 with less than a .5c swing since last night. I just bumped it to 21c since it is proving to be stable.

I have accepted this setup will not let me cold crash, but for Ales between 16-21c it is looking ok, especially once I have the Conical and jacket for it in November.
Aquarium chiller is something to look at, I did see some comments around though that wrote these off as not powerful enough.

I'll answer a few questions too.

Why not a fermenting fridge?
- I was using one, but it died. With 4 people in the house, it had to double as a normal fridge when not fermenting beer, in a 2 car garage with 2 cars and way too much crap everywhere.
I have my own corner with some shelving and my keezer near the door to the house, but past the keezer and where the fridge was, one of the cars parks right in front. Made it difficult to check.
This isn't my house, and I'd rather use my existing space.

Ambient temps - 
I initially said 28c as that is what it was then, the garage fluctuates and lately it's been closer to around low 20s. No doubt this is helping the cooling capacity remain "good enough".

Using Radiators-
I did think of this, I have closed loop watercooling gear around the place for PC cooling, but the size of radiators had my wondering about how fast equilibrium would be reached.

Just had a look at your thread cke11y, would love to see some pics of the setup, as FTSS gear is what I am looking at as well.


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