Temperature controlled valve

[DamienM]

Hi All,


I'm really just after some ideas on where to start.


What I want to be able to do is control the flow rate of water (cold) through a condenser system of between 0.2L p/min up to about 1.5l p/min to maintain a steady temperature of the condenser unit.


For example if the temperature starts to rise in the unit the flow rate will increase gradually to bring the temperature back into a 2deg C range of say 78-80. If the flow rate is too high and the temp drops below 78 it reduces the flow rate to bring it back into range. It’s not critical if it goes +/- 5deg C as long as it returns to the 78-80 range within say 10 seconds. I am currently doing this by hand and its pretty tedious as the process can take many hours to complete.


As mentioned not after the solution just some pointers I was thinking RasPi or Arduino to control the valves and communicate with the electronic thermometer.

Yes I’m making essential oils



What do you think?

Damien

 

[hevans1944]

You should be able to do this with an all-analog PID controller. Many of these available off the shelf. Of course you can take a digital approach, too, using Arduino to mediate between electronic thermometer (whatever that is) and your valve(s). That's probably what I would because (1) it sounds like fun, (2) could be cheaper, (3) there are a lot of folks here that would/could help.

There are lots of problems associated with closed-loop temperature control, but the most serious is response delay, the time between when the system realizes a correction is needed and when that correction actually affects the temperature being controlled. A finely tuned PID controller will help to solve most of the problems, and you have your choice of an analog or digital implementation of the PID algorithm. You should also have some familiarity with thermodynamics. Things usually get hotter a lot faster than they get cooler and that affects the control algorithm.

I realize you are just asking for suggestions and ideas, but it would really help if you could sketch out on paper what you are trying to DO instead of setting in concrete right now how you plan to do it. For example, what is a "condenser system" and how is heat exchanged with your "essential oil" (fractional distillation?) process? Do you have a distillation column with a linear temperature gradient that you want to control? I assume this is a home project and not on the level of complexity of an oil refinery.

 

[Wakoli Chokeli]

Well said Mr. Hevans'. Let me know if you are going for arduino, will be happy o help. Raspberry will be bigger for the project I think.

 

[debe]

This is what ive been using for refrigeration control from Ebay China. They work well & are only $2.50 free freight & are quite verasatile in its programing range.

 

[DamienM]

Thanks for the feedback guys,

To give a little more info yes it is Fractional Distillation I am doing with a constant stable temperature water source (not a looped system) where water comes in the inlet circulates in the reflux condenser exit outlet A then enters the primary condenser unit before exiting outlet B. I don't have it pictured but the manual flow controller is connected to the outlet B port to ensure positive pressure through the system. Likewise not shown is the Thermometer however you can see on the attached pic where it sits. To maintain the temp I adjust the outlet flow to raise or lower the temp, it is quiet responsive however a time delay of 15 seconds is acceptable. In fact thermodynamics in this case works in my favor as I want the drop in chamber temp to be slower then then temp rising, see the system is harder to regulate if it gets to cold but it also takes longer to cool as you stated.

I can keep doing this manual however as you mentioned Hevans where is the fun in that and I like the idea of Arduino. I mentioned the RasPi as I have been working with them at work in a trucking solution we have just created as a bridge unit between a $4000 zone one tablet (Latest tech) and an Acme 6000 (rs232 tech) utilizing the Pi's wireless connection, some creativity and the magic of serial to USB convertors.

Debe I like the product but I'm not sure if it will have the accuracy or responsiveness to control for this task though I could be wrong

Thanks again guys, of and I state essential oils as the other product is a we bit naughty

Cheers