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Packing headspace and coolant

PostPosted: Sun Sep 18, 2022 8:12 am
by NFI
I have a FSD Mac4SS with 500mm packed section with 4 rolls of 100mm copper mesh which still leaves me with 100mm of headspace.

Is that headspace a must or could I still put more packing in to fill it to the reflux column?
Would it have any effect either way?

Kind of unrelated related but...
Is there a theoretical correct temperature/temp-range of the coolant passing through the reflux condenser? (My concern being that my coolant water may be too cold in winter)
Would hooking the inlet of the RC to the output of the PC assist in slightly heating the coolant?
As my reflux condenser inlet needle valve is only open 1/8 of a turn during the body of the run would I then have issues with the PC temperature?

Re: Packing headspace and coolant

PostPosted: Sun Sep 18, 2022 9:12 am
by Wellsy
Morning NFI
I believe you would be fine to put more packing in and that should result in a cleaner product , more packing equals more reflux/ stripping of flavour so cleaner product. Well at least that is my understanding but I have been wrong before lol.

As for the reflux water temp I believe everyone has variations and that is why there is no consistent setting that we can all use, my temp changes over the run so I need to tweak the rc water flow. As for preheating by the pc outlet I don’t believe that will work as the pc outlet won’t heat up until after it has passed the rc. If you restrict the flow of the water going through the rc it will effectively restrict the water flow through the pc and result in vapour/product escaping.

Well that’s my understanding anyway mate I am sure other will correct me if I have misunderstood

Re: Packing headspace and coolant

PostPosted: Sun Sep 18, 2022 9:33 am
by BigRig
if you are concerned with cooling water being too cold then you could always wrap the hose around the boiler a few times to act like a pre-heater.

I personally gave up running my still in the cooler months and now enjoy an off season watching the footy :laughing-rolling: .

Re: Packing headspace and coolant

PostPosted: Sun Sep 18, 2022 11:22 am
by howard
my water never changes during a run because it's circulated from the swimming pool.
however, the temp of the pool water ranges from 15c-30c during the seasons.
this is not usually a problem, as on a reflux run, i gradually close the water valve after being in full reflux to EQ the column.
i already know the approximate setting of the valve to allow vapour through.
by closing the valve slowly and waiting/observing until i get vapour through the RC (usually) gets me on the money, whatever the temp of the water.

Re: Packing headspace and coolant

PostPosted: Sun Sep 18, 2022 12:22 pm
by NFI
Thanks guys. :handgestures-thumbupleft:

Re: Packing headspace and coolant

PostPosted: Mon Sep 19, 2022 12:41 am
by RC Al
In theory you want the output water temp of the rc to be as close to the vapour temp as possible, the reflux going back to the plates/packing will be hot and require less energy to reboil/flash in the column.

This allows for either: a slower rate of boil for the same output speed, which leads to better seperation (cuts) - Or a greater output for the same energy use.

Win win for whatever type of product your making.

This is why I'm on the counterflow rc side of the fence, ie water in at the top - making that work the other way won't happen

Re: Packing headspace and coolant

PostPosted: Mon Sep 19, 2022 7:32 am
by NFI
RC Al wrote:This is why I'm on the counterflow rc side of the fence, ie water in at the top - making that work the other way won't happen


I always see people saying "water has to go in at the bottom and out through the top to prevent an airlock in the condenser" I was not even aware that there was an opposing view on that, interesting and something worth investigating. Thanks RC.

I hook my cooling water up to my tanks via our house pump ( I switch the house over to town water for the run). The pump has a lot of grunt and flow rate as it has to lift water up to the on roof solar hot water and we get high pressure/volume hot water output. When I hook it to the Reflux condenser (off the still for cleaning/testing) and with the condenser and tank taps fully open the pressure and flow rate coming out of the condenser is greatly diminished, a bit like a bubbler drinking water tap, the inlet hose is hard and bulging from the pressure. Is it normal for the defleg to have that much restriction/backpressure, I was quite surprised really.

Re: Packing headspace and coolant

PostPosted: Mon Sep 19, 2022 1:33 pm
by howard
if it's a shotgun type of condenser, they have spacers inside which will probably cause some resistance.
factor in the inlet size of the condenser and the grunt of of a house pump...............
i'm guessing the pump is a pressure pump?
maybe there's a pump guru on here, but i'm thinking that for the health of the pump v a lower still pressure delivery, maybe fit a valve bypass back to the tanks?

Re: Packing headspace and coolant

PostPosted: Tue Sep 20, 2022 8:43 am
by RC Al
:text-+1: with howard on that.

Im guilty of not using a bypass with my set up, a reconfigure is due atm anyways, might have to buy a valve or two this week..