Brewing Under Pressure with an iSpindle/Tilt

[Petrolhead]

I’ve started brewing under pressure with my Fermzilla Allrounder and wondered if this effects the accuracy of my iSpindle, or a Tilt.

My thoughts are that if it does it is fairly insignificant. If the ’tube’ on both isn’t compressed then the displacement stays the same so the buoyancy remains unchanged.

If the tube was open then the buoyancy would change....and of course the wort would ruin the electricker! Anyone brighter than me got some thoughts above my school boy physics?

 

[DocAnna]

I’ve started brewing under pressure with my Fermzilla Allrounder and wondered if this effects the accuracy of my iSpindle, or a Tilt.

My thoughts are that if it does it is fairly insignificant. If the ’tube’ on both isn’t compressed then the displacement stays the same so the buoyancy remains unchanged.

If the tube was open then the buoyancy would change....and of course the wort would ruin the electricker! Anyone brighter than me got some thoughts above my school boy physics?

Full disclosure I don't have an iSpindel, I just enjoy the physics.

The buoyancy within the liquid will be effectively unchanged since the force keeping it afloat is equal to the mass of liquid displaced. For a constant mass which the iSpindle is, the mass of liquid displaced will also remain constant, with the volume varying on the density (or gravity) of the liquid. However, the displacement of the gas in the fermenter also has a buoyancy force which is equal to the mass of gas displaced. Eg in a helium balloon, the ballon floats even though the balloon has mass since the mass of the volume of air displaced is greater than the total mass of the balloon. For most environments the mass of air/gas displaced provides so little buoyancy that it is not relevant. However, in a high pressure environment, with a hollow container filled with a gas at lower pressure the buoyancy theoretically could be relevant. I'm going to quote buoyancy force as mass rather than Newtons as it's easier to make sense of.

The following is based on a volume of 20ml of iSpindel above the fluid level, at 20 degrees C.

At (1 bar) atmospheric pressure 20ml of air displaced by an iSpindel would have a buoyancy mass of 23.8mg
In CO2 headspace due to the greater mass of the gas, the buoyancy mass is 36.1mg
So the effective weight of the iSpindel in CO2 would be 12.3mg less than it was when you put it in to the wort
At 1 bar additional pressure, ie pressurised to about 15psi, the buoyancy mass is now 72.2mg
So the effective weight of the iSpinel in CO2 is 48.4mg less than it was when you put in the wort.
The difference in pressures thus would yield a difference of 36.1 mg in effective weight in the liquid phase

This is complicated by the small angular movements of the iSpindel in the fluid varying the volume of displacement and that a different temperature will vary the mass of gas for any given temperature.

The short version is yes gas pressure would be expected to have a very very small effect on the buoyancy of the device in the gas it is in which would translate into the amount of liquid displaced and the angle of the device. Whether that is remotely recordable at the sensitivity of the device I really don't know.

Anna

 

[Obadiah Boondoggle]

I am sorry, but I can not help you with your physics question

I am, however, confused about your location

You have it listed as my shed

Well I am also in my shed and haven't noticed you there - although I do keep hearing voices

Up to now I have always believed them to be the voices inside my wife's head telling me what to do

What are you wearing so I can look out for you?

 

[RGeats]

I too brew under pressure with a tilt. However I haven't noticed it being less accurate than brewing at ambient pressure. Each isn't particularly accurate for me, but I don't care I am using the tilt to track the change of gravity, if it is out by a few points it doesn't really matter. I'll take a sample at the start and end and use a hydrometer to measure the gravity.

 

[zeptobrewer]

At high pressure there will be more CO2 dissolved in to the beer, so it gets progressively less dense as the fermentation continues. This is true during regular fermentation too though, and I get good results without adjusting for that.

If you have ability, force carb some liquid of a known gravity (plain water?) and see what sort of results you get. I'd expect the difference to be minimal, but interesting!

 

[Cheshire Cat]

I'm always under pressure when I brew from my wife talking about the steam and smell to my need to get things right. How can this ispindel help me?

 

[Obadiah Boondoggle]

Well an Ispindel keeps you under pressure not only on brew day but also during the whole period of fermentation giving you 4 updates per hour as to how your attentuation is doing. Temperature readings are equally as frequent so you can fret over whether to turn the heating mat off or on

You could always buy an Inkbird Thermostat to add to your arsenal, so you can relax about the heat pad and worry about whether you have the settings right on the Inkbird

Bearing in mind that the human race has been brewing beer for over 10,000 years - how did they manage without an Ispindel or Inkbird?

 

[Petrolhead]

So in a nutshell DocAnna the displacement will remain constant if the volume of the tube remains constant, ignoring small changes of density with pressure, so providing the ispintiltythingy doesn’t deform we are ok.

Happy days....

 

[Joe01522]

I’m wondering a similar sort of thing...

I thought I was pretty much at the end of fermentation, so dry hopped thinking a day more fermentation, few days increase the temp then cold crash. As I dry hopped I swapped my airlock for a spunding valve set to 25psi, and let the pressure build naturally.

Since then though it’s continued to drop a gravity point every few days. I can’t decide if it’s still fermenting or the co2 dissolving in the beer is causing the steady drop. I’d really like to cold crash so I can rack the beer off the hops before they’ve been on too long.