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PID control of coolant temperature for dephlegmators

These are various style condensers for many different applications.

Re: PID control of coolant temperature for dephlegmators

Postby jake_leg » Thu Apr 05, 2012 6:56 pm

Not sure I buy the overcooling idea. There is a gradient of temperature in the dephlegmator. I have almost zero experience with CM though.
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Re: PID control of coolant temperature for dephlegmators

Postby Smaug » Thu Apr 05, 2012 7:13 pm

Just run it so that your discharge is a pencil lead size...

Control your flow so that ya piss like a pot still and it won't matter if ya break your spirit alcho. by the light of the moon.

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Re: PID control of coolant temperature for dephlegmators

Postby pintoshine » Thu Apr 05, 2012 9:28 pm

Jake_leg you have the proper idea of PID, the functions that rednose uses are extras.
PID once tuned, becomes adaptive and predictive in the process you are trying to control. The temperature change lag time has always is very hard to tune in. PID usually changes too fast. If you can set the parameters correctly, a PID system can hold you at near perfect temperature with no variance. Unlike the on/off with a deadband, PID is very nice in its ability to create stability.
Many don't know how PID works but in a nut shell it provides proportional power of change to the error measured. It integrates the the error to come up with a total error over time and it uses the change in error to help identify how drastic to change the power.
So the parameters are initially hard to control. Many of the modern PID controllers have a learning mode.
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Re: PID control of coolant temperature for dephlegmators

Postby zedzedtop » Fri Apr 06, 2012 3:24 am

Well, in a sense, nobody but the engineers at the company really know how they work. The algorithms are proprietary. For instance, if you knew the physical parameters of your system... conductivities, spec. heat etc, and you knew what the pid was actually doing, you could set the pid parameters to have it work optimally. Instead, you use 'informed' trial and error or 'AUTOTUNE.' Believe me, I spent many hours in grad school trying to extract info from Watlow about their pids.

So what is it about these stills that we are trying to keep constant, and why? Those who run electric stills have another precise way to regulate performance, but manipulation of this variable seldom gets mention.
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Re: PID control of coolant temperature for dephlegmators

Postby pintoshine » Fri Apr 06, 2012 7:38 am

I generally try to keep the top of the column vapor temperature as low as possible when making vodka while maintaining a fast take off rate. On pot stills I try to keep the product temperature acceptable but control the cooling water to the condenser to use as little tap water as possible for clients that have no circulating coolant.
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Re: PID control of coolant temperature for dephlegmators

Postby zedzedtop » Mon Apr 16, 2012 2:34 am

I've built (almost!) my still to have an RTD monitoring the water output of the dephlegm. Water flows in the top, out the bottom, counterflow, as has been recommended many times. I'm curious why it's better to monitor the output of the coolant water, and not the vapor temp?
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Re: PID control of coolant temperature for dephlegmators

Postby Rumdog » Sat Oct 25, 2014 4:56 am

How would a marine water chiller go.
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Re: PID control of coolant temperature for dephlegmators

Postby pintoshine » Sat Oct 25, 2014 7:40 am

zedzedtop wrote:I've built (almost!) my still to have an RTD monitoring the water output of the dephlegm. Water flows in the top, out the bottom, counterflow, as has been recommended many times. I'm curious why it's better to monitor the output of the coolant water, and not the vapor temp?


All the systems for deph control I build always monitor the cooling water in the dephlegmator and the top plate temperature. Only the dephlegmator water temperature tracks foranything meaningful. The plate temperature is too slow to react to.

I was wanting to ask about the in from the top method. I am assuming only a coil type dephlegmator. If it were a tube and shell dephlegmator this would not work. An air pocket forms at the top and can only be elliminated by circulating bottom in top out.
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Re: PID control of coolant temperature for dephlegmators

Postby acfixer69 » Sat Oct 25, 2014 8:52 pm

I'm not sure I understand Pint

I feed my shotgun deflagmator on the column in the top and out the bottom, counter flow and control the flow out the bottom and monitor and regulate the temperature there. I put a coin valve at the top to check for air as that question has been here before in Swedes build. If I start up and let it run for the stabilization of the column I never get air or need to bleed off any air.

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Re: PID control of coolant temperature for dephlegmators

Postby punkin » Sat Oct 25, 2014 9:26 pm

I do the same. I have a valve in the inlet line on a tee to bleed off air. Counterflow is always best as far as i understand.
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Re: PID control of coolant temperature for dephlegmators

Postby pintoshine » Sat Oct 25, 2014 9:44 pm

Well, now you tell me about the air bleed off. :doh:
These are kinda rare in most commercial setups. The bulk and short height of these exhibit no difference in counter flow or otherwise. So for simplicity sake, in the bottom and out the top. Never have to worry about a vapor lock or trapped bubble.
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