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I hope I am able to ask this in the way I am thinking about it. Is there a point, or at what point does water become ineffective for heat exchange.

The reason I am asking, (My real world experiences.
When using our distillation unit, before We had what we have now, I used to have to keep my cooling water in 200 gallon tank, this would start off very cold, around ground temp 65 F or so. Using the water at this temp, We noticed that you get condensation mix in. Kinda like the sweat from your Cold drink on a summer day, (while making Fuel this isn't wanted) as the heat exchanger does its job, the reserve tank heats up. Now of course I have always thought that I needed to keep the water as cold as possible, Though it seemed that when the cooling water heated up closer to the point of the distillation, It seems to be more efficient/effective.( I don't know why I thought it was more effective, It just seems like I could really turn the heat up on the boilers and it would just rumble and produce massively)
This doesn't seem like it should work that way..
Which is why I am here asking for guidance. I would think that the coldest water would be the best. However you get a lower distillate, due to sweating. You can collect faster over all, because you can run it harder,but with purity loss from condensation. Heating the coolant water up to a steamy 120 F and it still does what it is supposed to do, Condense the final product. I am still able to run the machine hard, but you do notice the heat. Product out-put would still be high, But you can't run quite as fast as you can with very cold water since you could possible blow steam past the heat exchanger. However you don't have to worry about having condensation built up. Either way, I know they both work, I was hoping to know why one is better than the other, If that makes sense.. Thank you for any insight. Hopefully how I asked wasn't to jumbled up. Though I fear it may be, writing as you see is not at all a strong point for myself.

Cole Goodman
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  • I don't know your distillation set up but assuming the condenser/refluxer is at the top, shouldn't it be sufficient to switch on the condenser cooling water as late as possible? E.g. when the vapours is nearing the top/condenser? Once the column is filled with product vapours, the type of 'sweating' you describe is no longer possible. – Gert Jun 23 '16 at 14:35
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    This question is very difficult to answer as it is written. Please provide some type of schematic showing your situation. Also, what are you distilling? Is the distillation a batch process or a continuous process? What are you using to boil and condense the feed material? What pressure are you running your still at, and what range of pressures are acceptable? What compositions are involved, and what distillate purity do you need? Are you using reflux? In other words, a LOT more information would be very helpful. – David White Jun 23 '16 at 15:47

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