[conspire] sous vide question.

[Ivan Sergio Borgonovo]

On 10/25/2017 06:46 PM, Rick Moen wrote:
> Quoting Ivan Sergio Borgonovo (mail at webthatworks.it):
> 
>> I do work with this stuff. Depending on several factors I witnessed
>> temperature gradients of more than 4C in less than 20cm deep tanks.
> 
> I bow to someone who's actually done the measurements, instead of merely
> owning an accurate thermometer and making shirtsleeve speculations about
> skillets full of water.  ;->

I really didn't have to assure uniform temperature and so I didn't have 
to solve the problem, just be aware of it, since temperature was 
measured indirectly etc...
Actually I was quite surprised myself.

I did many tests with several sensors at a time and if I had to model 
the problem I wouldn't be happy.

What I've learnt is that it depends on too many factors:
- kind of heater (immersion, adhesive on the walls, on the bottom)
- geometry of the tank
- geometry/volume and heater power (speed at which you heat the water)
- stuff you put in and how
- thermal isolation of the tank
- temperature of the water

I think external boilers with pump may be a necessary solution if you've 
larger volumes of water and more precise temperature regulation.

Anyway, I was mostly interested to heat the water fast and be sure the 
temperature didn't drop below a certain level.
Something in the setup made things really worse for temperature 
uniformity: immersion heater and some stuff inside the tank that was 
causing far from ideal convection flow inside the tank.

I'd think in normal cooking pot things should be easier.

I gave a look to sous vide supreme video and they use a grid at the 
bottom to circumvent the problem.

-- 
Ivan Sergio Borgonovo
http://www.webthatworks.it http://www.borgonovo.net