Recovery calculations, I believe the heat needed to vaporize DME at a rate of 1 lb per minute is 3,170w.
Using my 800w sous vide heater I should recover at a rate of 1 lb per 4 minutes at 100% heat transfer efficiency. At 75% transfer efficiency I should recover a pound of DME every 5 minutes 20 seconds.
I took the equations posted by @TheGratefulPhil and filled in the DME data. This site has some really detailed technical information if you know what to search for!
My next addition to this system is going to be making 2x DIY 8k BTU glycol chiller loops that are cooling 2x plate heat exchangers. I’ve got dual recovery lines, so I’m going to put a plate exchanger on both lines. I know it won’t condense in the plate exchanger, but it should remove most of the heat energy before it goes into the tank, so my dry ice lasts longer. I’ve got to drive an hour each way to get dry ice, so I want to make it last.
@Rowan do you think I would be better putting both ACs in a single glycol bath or use a separate bath for each chiller? I saw your thread on making them, it was an excellent read!
Thanks! I found so many of your posts when I was doing my thermodynamics research, technical search terminology is a direct line to your posts. You listed it all too, even the matching dry ice sublimation rates (which I’m fairly certain was 5g/s) for 1lb/min n-but.
Hopefully I got everything right, because this is the first time I’ve seen these calculations for dimethyl ether.
Unfortunately I don’t have a mini-split, but I do have 6 extra 8,000 BTU window units from when I was running multiple grow houses.
Once I find a competent and discreet HVAC tech in CO I’m going to have the evaporator cut off these units and pump the refrigerant directly into the plate heat exchangers. The plate heat exchangers I’m looking at from AlfaLaval are able to run even with higher pressure refrigerants like r410a, hell they can even run CO2 as a refrigerant with their tolerance, but I’m not sure of the best refrigerant choice for this project tbh, which is why I want to employ a tech.
I"m not a fan of how poorly it accepted torque. Seemed to deform as easily as PTFE. Have you seen envelope gaskets? PTFE wetted surfaces, FKM interior for spring and resistance to deformation.
No, the SMS gaskets are glyon, and they were crazy expensive. Interesting that you had issues with the Tuf-Steel, they were highly recommended when I saw them mentioned here. Are you doing the recommended 50 lbs?
What kind of psi can envelopes handle? DME has a pretty high vapor pressure, if I’m making crude it will be running ~130 psi. Normal recovery temperature will be 75-80°F, and that’s ~100 psi.
Have your vapor enter through the top port of the plate. That gives you counter current exchange and also allows gravity to aid in draining the solvent once condensed. It also helps maintain maximum surface area available for condensing. Keep in mind that routing post condenser is huge unless using a pump, don’t want to create a P-Trap in the plate… So make sure you gravity drain into the take post plate.
Ha, I didn’t even notice I put the solvent exit on the top when I made the drawing. Definitely wanted gravity to assist the solvent draining with counterflow for the refrigerant. The plan is good though? I’m a total novice when it comes to refrigeration, literally my first project with it ever.
Just checking chemical compatibility, pressure and temp. Safety is everything, so lots of PRV’s. If ya got any questions during the way just DM, I’m glad to help!
Have built 100’s of closed loop machines but never a DME setup, always fun playing with new solvents.
It definitely will, I just Googled “tube and shell r410a” and there was a whole page of products. I specifically looked for 410a because it runs at a higher pressure so the engineering would be more solid.
