so in my search for an oven ive come across many brands styles shapes and sizes.....
its all very straight forward except for one tidbit when it comes to the actual name of the device.
Some are referred to as vacuum ovens, while some others are referred to as vacuum drying ovens
is there much, if any difference between them? from everything that i can read and see pics of, its just another name for the same machine. But i could be wrong... so if anyone has any insight into this it would be much appreciated
-oak
Solly, my experience with the plethora of different brands is limited, but we started with rebuilding a Napco vacuum drying oven, used to dry pharmaceuticals under vacuum. A robust oven, with only bottom heating and capillary tube mechanical controls. After moving one of the heaters to the top, adding three thermocouples and PID controls, it did a good job.
While looking for an off the shelf solution, we did a joint R&D project with Cascade TEK, and highly recommend their TV0 series with Welch pumps. We are still experimenting with our original loaner TVO-2 test sled, and my SPR partners have each purchased one for their own businesses.
We also experimented with an AI, and suggest that you look not only at features, but under the skin to better understand the differences between ovens.
The AI did the job, which is what we hire ovens for, but in examining the Napco, the Cascade TEK, and the AI undressed, I noted the polymer tubing plumbing on the AI, ostensibly silicone rubber, which given time will deteriorate, while both the Napco and the Cascade TEK use hard tubing.
Hee, hee, hee, to show that AI was paying attention, enter their newest market entry, their Elite series, which is hard plumbed and which offers a 5 sided heating solution.
To add to the anticipation, the former Cascade TEK Botanical program manager, now employed at Sweetleaf, conspired with Maxwell @ AI, and requested SPR lab space, along side the Cascade TEK TVO-2 test sled, to put an AI Elite through its paces and compare the differences. How could we resist and I'll share more when she provides the pari passu test comparisons.
In general what our vacuum oven research has shown, is that the oven is a inner can, with a door. That can is reinforced to withstand vacuum with structure of some sort, and the can is typically heated by attaching heating elements of some type on the outside.
The simplest have heating strips bolted to the bottom, and the more elaborate ($) units put elements on all sides but the door, so that heating is even.
Heat is a central issue in a vacuum oven, because there is no convection in a vacuum, leaving only radiation and conduction to transfer the heat from the oven walls to the product.
That is where the shelves come into play. Solid robust shelves firmly attached to the oven walls will conduct more heat than wire shelves sitting on shelf brackets.
The greater the mass of the shelves, the better they hold heat when the oven door is open, but the longer it takes them to change temperature as well, after you have dialed in new parameters. Some folks add marble shelves to act as heat sinks and better hold heat.
The best solution appears to be individually heated shelves, with individual thermocouples and discrete PID controls.
It goes without saying that good temperature controls are a key issue.
Good vacuum control is handy as well, especially in the initial stages of purging and having a pump rated for chemical duty allows you more latitude than one which requires constant monitoring and oil changes. For what we are doing in the oven, it isn't necessary to pull hard vacuums into the low micron/militorr range.
We like to stream or backfill with nitrogen, so the oven vents need to accommodate that plumbing.
We continue to use the port in the back of our TVO-2 test sled for accessories, like the gas analyzer and especially as a pass through for inside thermocouples, so it has turned out to be a nice feature.
Visibility is key, because you have to see what is going on to produce artisan concentrates, so a good window with adequate indoor lighting.
A bunch of small ovens would be more effective at artisan quality than one big one, because you have to not only be able to watch the patty, but you must be able to adjust the conditions for just that patty, and the more you have, the greater the variability and difficulty in keeping them all in the sweet zone.
