After applying vacuum in mixing vessel Temperature decreased??

Actually it has a lot to do with boiling. Water has a very high latent heat of vaporization. Lower the pressure until the boiling point is below the temperature of the batch and it *will* boil. The heat for the change of state (539 cal/g) will come from the batch itself and the temperature will drop dramatically until it drops below the boiling point for the current pressure.

Ok I haven't used any real values just reduced pressure from atm to 0.5 bar at an example temp.,
Boyles law:
Pressure Start x Volume Start = Pressure End x Volume End
Temp Start Temp End

You switch this round so you see your Temperature End:
Temp End = (Pressure End x Volume End) x Temp Start
(Pressure Start x Volume Start)

Close lid, before you apply vacuum Volume End = Volume Start so remove from the equation:
Temp End = (Pressure End) x Temp Start
(Pressure Start)
Before applying vacuum
Temp End = (1 Bar) x 23 deg C
(1 Bar)
Temp End = 23 deg
After applying Vacuum
Temp End = (0.5Bar) x 23 deg C
(1 Bar)
Temp End = 11 deg <- lower temp

That's the the way the Law works (I think) as explained verbally in the responses above

There is more going on here than just the cooling effect from lowering gas pressure. It does indeed have to do with boiling, or specifically the energy required to make a phase change between liquid and vapor. When you reduce the pressure then the boiling point of the water plunges. Once it begins to boil in undergoes a phase change, and energy required to make the phase change is significant. That energy, called the enthalpy of vaporization, must come from somewhere. In this case it comes from the water because the energy rate from vaporization is greater than the energy input rate from your heating jacket.

If you were to place a container of water in a vacuum chamber with no heat input for long enough you can actually freeze that water in mid boil, preserving the bubbles and boiling surface of the water in a solid ice. After that the ice then sublimates directly to vapor.

But you don't take only my word for it. Here is a youtube video that shows the OP exactly what is happening in his system and explains why.

https://www.youtube.com/watch?v=glLPMXq6yc0

Gripster,

It's not that Boyle's law doesn't work. It's that it isn't responsible for the observed phenomena. Boyle's law covers changes in gas. It does not cover change of state.

In Puerto Rico asked for a cold beer. The bartender took the bottle out of the cooler, thumped the bottom on the bar several times snapped off the top and handed it to me.
By the time it got to me it was frozen and the bartender asked if it was "cold enough".
He kept the beer near freezing, when he thumped it he added energy, when he took off the cap the pressure was released and the liquid froze.
That guy in India needs a beer.

gas said:

In Puerto Rico asked for a cold beer. The bartender took the bottle out of the cooler, thumped the bottom on the bar several times snapped off the top and handed it to me.
By the time it got to me it was frozen and the bartender asked if it was "cold enough".
He kept the beer near freezing, when he thumped it he added energy, when he took off the cap the pressure was released and the liquid froze.
That guy in India needs a beer.

Click to expand...

I will have to verify this tonight... may take 6-10 to prove your theory



Hey Connolly, nice to see you have stopped by have you been busy? have not seen you around lately

geniusintraining
After 10 it works every time.

BEER[32] so you aren't wasting space

For example...sort of like Acteone...It is cool when splashed on your hand because of "evaporative cooling". Its "vapor pressure" is near ambient temperature and atmospheric pressure, so it is vaporizing (turning to vapor) and that motion causes a lower temperature.
The liquids in the tank are getting colder due to the evaporative cooling effect on the liquids that are vaporizing due to the lower pressure.

Knowing what the product is may help here. The jacket is filled with water, he has added water to the product, but we don't know what the product is nor how much vacuum is applied. If the product is something like ethanol, it would very likely boil under very little vacuum at 70 C. That boiling would scavenge a good deal of heat energy from wherever it could get it.

Any moisture in product will cool as it is evaporated under vacuum.
You can put a glass of water in a vacuum chamber and freeze it solid at ambient temperature, when you apply vacuum.

This is the reason that refrigeration systems work. The liquid has a certain boiling temperature at a certain pressure. If you drop the pressure below the boiling point at its temperature, it will boil and drop temperature. In refrigeration you will find very well defined preessure temperature graphs for refrigerant. If for example you want your r507 at -20 deg_F , you need to control it to 17.8 psig.

gas said:

After 10 it works every time.

Click to expand...

Need more research... I think tonight I will try it with tequila, should be a little harder to freeze with the higher alcohol content... but I will give it my best shot

May need a few weeks of research