Doubleuj wrote:Ideally water should run in the opposite direction to your vapour BUT, in the case of your rc if you have the inlet up the top and only a trickle of water going it may drain faster than it fills and be ineffective. This is why we say inlet at the bottom on both. However, I still have my rc water coming in the top but looped the outlet water up above the inlet, creating a sort of S trap so it doesn’t drain, seems to work for me :handgestures-thumbupleft:
The RC fills up with air because the cooling water has dissolved air in it. Water dissolves more air at low temperature and when the cooling water is heated up, it degasses. If you have clear cooling lines you'll see this happening. It's the same reason why water in a saucepan will have little bubbles stuck on the bottom and bursting and reforming well before the water hits it's boiling point.
Anyway, if the water flow is downward in the RC (top to bottom) then the air bubbles that come out of the water rise up against the flow of water (which is a slow flow once we start collecting) and get stuck in the RC. What was once a RC full of water is now one full of air and water trickles down from the inlet and straight out the outlet.
Cooling water in at the bottom allows the flow of water to be in the same direction that the bubbles of air want to go (up). This takes most of the air with it (some will still get trapped). If the water didn't take the air with it then there would be a point where no flow would occur at all, but the pressure from our pump (which is small now that it's passed the valve) sees to that.
It's the difference between pushing water uphill or allowing it to fall downhill. The pump is doing no work in the second case, other than providing the next bit of water to fall downhill.
I doubt that a loop in a cooling line would stop the air staying in the RC. I think the pressure from the air in the RC will hold back the small amount of water in a loop. Have you tested it out to see how much water is left in the RC after a lengthy spirit run? I would suggest doing a run in each of three different configurations, one with the loop, one without and another without the loop but cooling water in at the bottom. You'll want to have some way of finding the volume of water left in the RC. Or measuring the air that comes out of the RC after putting the still back into full reflux after say an hour of collecting. This could be done by putting a clear container upside down over the top of the water outlet where it exits your cooling lines, simply compare the amount of air trapped in the container in each test.