View Single Post
Old 11-20-16, 02:29 PM   #9
Vapor Compression Goon
marx290's Avatar
Join Date: Mar 2013
Location: Portland, OR
Posts: 63
Thanks: 11
Thanked 22 Times in 11 Posts
Send a message via Yahoo to marx290
Default Went to long on a single post!

The next two are pretty recent. The hyperboloid condenser was neat looking, but it didn't have enough tubing or surface area to effectively dissipate the heat. Saturation temperatures on the high side were sometimes as high as 120 F or more. Subcooling was usually about 10 degrees. Circular construction is going to be a theme for this machine; I may eventually metal spin a brine tank for the evaporator which is shaped kind of like a bundt cake pan. The base construction and hole in the fridge will likely be round too, along with the bent laminated wood collar which will hold the controls and gauges, and will act as a cover to access the plumbing and wiring- if necessary.

This was originally supposed to have a sheet metal skin on the inside and out with the intentions of creating a draft for more effective cooling. That is why the posts are shaped and drilled that way. First attempt at assembly used 3/16" copper rather than 1/4". Lacing all those stainless steel posts (hand cut with shears and drilled on a press then bent with a cheap break) was exceedingly difficult. Imagine putting 16 keys on a key ring, but spinning them 16 times and feeding an additional hole with each one on each wrap. Think it would bind a bit? You would be right. I was able to complete the lacing, but it had a horrible taper and when I tried to fix it i just destroyed any symmetry it had.

I couldn't find anymore 3/16" tubing around town the next day, so I settled for 1/4" Drilled the holes out larger and even a little sloppy to make assembly easier. It has a slight inward taper bottom to top, so skinning it would have been difficult anyway. I decided to solder the copper to stainless posts and install it as is.

I'm happy to say that i have reduced the head pressure significantly, and improved subcooling to about 20 to 23 degrees. The ambient temperature in the shop varies dramatically, and It is getting a lot colder lately, so consistent data is hard to gather. I have tried a makeshift skin on the inside and out. It produced the draft I intended, but it wasn't enough I guess, and turned out to be a detriment to the performance. I like the exposed look anyway.

The next version will probably use 3/16" tubing. It will have a hyperboloid shape. I may split the 50 ft into two parallel runs, inside and outside coil, or I may run them in series. I will drill the holes, but then split them with throatless shears to give me fingers to apply the coils to and solder. More stainless steel surface area bonded to the copper would surely help.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
marx290 is offline   Reply With Quote
The Following User Says Thank You to marx290 For This Useful Post:
jeff5may (11-25-16)