How To Build A Cheap-ass Thermowell For Fermenter In 5 Minutes

[Whiteferret]

How much wort movement/circulation is there in an active fermentation? ie is there a difference in internal to external temperature locations. If you are measuring a point on the inside of the wort the outer layer(s) could be a lot colder. I dont know I have opaque fermenters so I cant see how much it swirls/agitates/mixes. Can anyone give any ideas as to how much there is?

ps my probe is in the air of the fridge
and I have a PC fan ciculating it :icon_cheers:

 

[shadders]

How much wort movement/circulation is there in an active fermentation? ie is there a difference in internal to external temperature locations.

depends on a lot of things, which part of the fermentation cycle, health of yeast, nutrient value of wort, temp etc... I've had AG brews pitched on the trub of the last brew that looked like there were eels swimming in it within 12 hours... On the other hand I've had lagers with a packet of s-23 pitched dry on top and those you couldn't see any sign of activity for most of the ferment.

I would guess for most mild ferments in a fridge the cooling would promote a current down the side of the fermenter, into the centre then up the middle. Cold wort at the sides would sink, pulling wort from the centre to replace it, once it gets to the bottom it's got to go to the centre. Though how fast that is depends on all the above.

 

[shadders]

QB from a couple of weeks of steady observation I can say that the fridge gets to it's thermostat cutoff temp much faster that the fermenter reaches the set temp. A few minutes Vs 1/2 - 1 hr. That's for a normal cooling cycle, i.e. after the wort has been brought down to within the fridgemate range. The off cycle is quite long (can be a few hours) and the fridge ambient temp gets up to pretty much wort temp in that time.

 

[DanRayner]

Good scientific debate going on right here. I like it.

 

[jonocarroll]

QB from a couple of weeks of steady observation I can say that the fridge gets to it's thermostat cutoff temp much faster that the fermenter reaches the set temp. A few minutes Vs 1/2 - 1 hr.

As I would assume - won't take long to cool down 50g of air.

That's for a normal cooling cycle, i.e. after the wort has been brought down to within the fridgemate range. The off cycle is quite long (can be a few hours) and the fridge ambient temp gets up to pretty much wort temp in that time.

This also seems normal. One would expect the off cycle would be long if the fridge is well insulated and there is not too much heat generated by the ferment within that time (heat that is generated, and propagated to the probe).

But is the off-cycle longer/shorter if you turn the dial up? I suspect it's not either.

 

[speedie]

4.18 is the specific heat of water ie kilo joules per kilo gram
not wort or fermented beer
so be scienitific please

 

[speedie]

the delta proportion of any control is either inherent or setable
if you are discussing a lame fridge stat it is generally about 2-4 degrees
if you are using an eletronic device it maybe setable to .1 of a degree
but this is not a good pratice as the fridge motor needs an extented off cycle for the gas to equalise
thus decreaseing the starting current on the motor due to both sides of the pump being equal
for HOME brew stick with a flucuation in control of 2 degrees
here is some thought for you what gives raise to the heat generated during the fermentaion process
is it friction or some unexplainable chemical reaction
or is it the heat of evoluation
speedster

 

[Online Brewing Supplies]

Whoo hoo this is really getting interest / confusing and probably a little technical for me. I leave it up to my high tech devises to do this stuff for me. Plan right and put the right gear/software in and there is no problems.
Nev
GB

 

[barls]

wrong speedie.
you can set your device as low as 1 degree difference so long as you have a decent compressor delay set so not to over heat the compressor. mine has been set at one degree difference now for 4 years, the compressor only kicks in once every 3 hours in winter and a little bit more in summer.

also you are still going on about this friction in fermentation. its not that you idiot, its the byproduct of the living yeast transforming sugars in to alcohol. just like your body giving off heat as it burns sugars.

 

[jonocarroll]

20L wort, assumed similar to water

4.18 is the specific heat of water ie kilo joules per kilo gram
not wort or fermented beer
so be scienitific please

here is some thought for you what gives raise to the heat generated during the fermentaion process
is it friction or some unexplainable chemical reaction
or is it the heat of evoluation

Oh. Your. God. I just hurt myself laughing at the irony.

If you have the specific heat of wort, please, by all means, post it. Particularly if it differs greatly from 4.18, and all the more so if it's off by three orders of magnitude. Oh, and the units are J kg^-1 K^-1. The word 'specific' in there indicates division by mass since it's an extensive quantity.

 

[shadders]

This also seems normal. One would expect the off cycle would be long if the fridge is well insulated and there is not too much heat generated by the ferment within that time (heat that is generated, and propagated to the probe).

But is the off-cycle longer/shorter if you turn the dial up? I suspect it's not either.

Without a concerted effort to measure it I can't say however my guess would be assuming both fridge thermostat settings produce the same bottom level wort temp:

Fridgemate Off cycle would be about the same for both since the wort has to heat from 18-20 deg in both cases.

Fridge compressor On cycle time in total would be about the same for both as it takes the same amount of energy to pump 2 degrees worth of heat out of the wort regardless of how fast you do it.

However total on time for the fridgemate would be longer in the case of a fridge thermo setting at 10 degrees. Lower thermal gradient = lower rate of heat transer. So whilst the total On cycle time for the compressor is the same it would be interspersed with more compressor off cycles. Probably more cycles of shorter duration.

After all of that we need to account for the lower lag between ambient temp and probe temp which should reduce the fridgemate on cycle. It doesn't actually need to pump the same amount of heat out of the wort because the lower lag means it stops at a higher wort temp than it would on the 0 degree fridge thermo setting.