Direction of flow, flow rate, output temp ?

[CROW-EATER]

I am running a offset head still, 2" column, 3" condenser with a double wound cold finger coil.

Can someone please clarify for me, in which direction should my water flow through my coil and more importantly, why ?

Should I be aiming to have the water exit at a certain temperature or is it best to pump as much cooling water through my coil possible therefore keeping the temperature of the coil as low as possible over its entire length ?

I'm pumping my cooling water from and returning it to a big rainwater tank so wastage is eliminated.
I have several types of 12 volt pump at hand, all with different flow rates and I can meter my flow rate with a valve if necessary.

Cheers

[Swedish Pride]

direction does not matter much
try to get the water coming out hot, hot enough to steam.

[CROW-EATER]

Is there any scientific reason why we should have the water exiting hot other than to ensure that water is not wasted ?

[still_stirrin]

Is there any scientific reason why we should have the water exiting hot other than to ensure that water is not wasted ?

It is the most efficient operation that way. But if you don't care about efficiency, there is still reason for the exiting water to be warm....it creates a temperature gradient in the condenser.

The gradient is important so you don't get "shock cooling", or rapid condensation in the column before the vapor has fully traveled up the column. Time of vapor flow and full travel distance (column height) as well as packing material are important to manage the refluxing vapors & condensing liquids. It helps with the separation of the distillates.

So, the warm to hot water exit is important for successful operation of your still head. When I measured my exit water temperature (do it by touch now), I ran the flowrate so the water temperature was around 120-130*F...warm to the touch, but not too hot to touch.
ss

[der wo]

Is there any scientific reason why we should have the water exiting hot other than to ensure that water is not wasted ?

The gradient is important so you don't get "shock cooling"

And a shock cooled product condenser can cause huffing of the still.

[Hound Dog]

Is there any scientific reason why we should have the water exiting hot other than to ensure that water is not wasted ?

It is the most efficient operation that way. But if you don't care about efficiency, there is still reason for the exiting water to be warm....it creates a temperature gradient in the condenser.

The gradient is important so you don't get "shock cooling", or rapid condensation in the column before the vapor has fully traveled up the column. Time of vapor flow and full travel distance (column height) as well as packing material are important to manage the refluxing vapors & condensing liquids. It helps with the separation of the distillates.

So, the warm to hot water exit is important for successful operation of your still head. When I measured my exit water temperature (do it by touch now), I ran the flowrate so the water temperature was around 120-130*F...warm to the touch, but not too hot to touch.
ss

In short, if the condensate is cold it will sit on top of the hot packing and not go down causing flooding.

[CaptMorgan]

I am running a offset head still, 2" column, 3" condenser with a double wound cold finger coil.

Can someone please clarify for me, in which direction should my water flow through my coil and more importantly, why ?

Should I be aiming to have the water exit at a certain temperature or is it best to pump as much cooling water through my coil possible therefore keeping the temperature of the coil as low as possible over its entire length ?

I'm pumping my cooling water from and returning it to a big rainwater tank so wastage is eliminated.
I have several types of 12 volt pump at hand, all with different flow rates and I can meter my flow rate with a valve if necessary.

Cheers

You want your cooling water flowing in the opposite direction of your vapor flow in order maximize residency time and build a proper heat gradiant. With a double wound coil, direction won't matter that much.

Target a max flow rate of 1 qt/liter per minute at max flow. When stripping, I let it go at max. When in spirit run, outlet temp of around 100-130F should provide for stable and efficient still operation. Make sure you have no alcohol vapor escaping. I want to figure out the temp where I start loosing vapor for my still and make sure I stay under that temp. All stills will have their own unique temperature.

[CROW-EATER]

Thanks for your great responses folks.

It looks as If I was on the right path, but it's always nice to be sure.

I have been running my coil so the top is the coldest but I'm not slowing the flow rate enough to get the exiting water hot or even warm for that matter.
Luckily the return reflux distillate is very hot anyhow probably due to design & heat soak of the 2" T pieces and valved area.

Next run I'll have a valve to control my cooling water, I might even have a play distilling water again.

Captain Morgan wrote ". Make sure you have no alcohol vapor escaping. I want to figure out the temp where I start loosing vapor for my still and make sure I stay under that temp. "
Interestingly on my first run (before my coil mod) I climbed up on the workbench and looked down inside my condenser, I could see exactly what was happening in there ... wet coils, 3 dry coils at the top and visible vapor droplets forming and dropping.
On the next run the ambient temperature was much higher and there was no dry coils at the top.
Here's some photos I took, I coukd wcen see what was happening right down the bottom at the valves although the photos didn't capture the visible vapor.

On that I've added a second 1/4" coil and a 1/2" return up through the middle, also a 3" cap to the top of my coil primarily to stop insects or debris falling in and blocking the needle valves, to centralize the coil and to ensure any airflow through the work area doesn't blow vapors from the condenser.
To the top of the 3" cap I have a 1/4" breather tube bent at 180deg pointing straight down, I can use this to smell if vapors are escaping. I am considering adding a airlock to the breather tube so I can see if the still is blowing or sucking.
Picture showing the 1/4" breather tube

Picture showing how the 2 coils both flow in tge same direction, looking at the bottom of the coil