Turbine cooling

Any questions about tools or supplies. Post your compressor/gun questions here.



Settled In
Posts: 14
Joined: Sat Jun 29, 2019 9:07 am

Country:
USA
PostPosted: Sat Jul 06, 2019 10:22 am
I've seen where a recommendation is to build a simple box and add ice packs for inlet cooling on a turbine for HVLP.

My question is has anyone tried setting the turbine up in front of a portable AC unit? It seems to me that the AC would cool the whole turbine, not just the inlet air.

I decided to try out my HVLP system by spraying some stain thinking that this is an easy test and allows me to get a feel for the system. The stain went on fine but I noticed that the info here is correct in that the air is really hot, and the turbine is hot enough that you don't want to touch it. While not a problem with the stain I was using (stuff dries really slow), I can see it being a problem with automotive finishes.

As a side note if anyone is interested, the Citation 4 and Apollo 7500 worked fine. Again, this was with stain so I can't see it needing much. The gun adjusted easily and predictably. And I have to say I absolutely love the 3m PPS system.

The only thing I didn't like has to do with cleaning the gun. Apollo designed it so it can be either a gravity cup (mine) or siphon cup. The unused port is plugged off with a cap. I initially cleaned the gun by spraying lacquer thinner through the gun thinking that's all it would need but I kept seeing dark fluid. Well the port gets filled and the thinner doesn't really flow though it. I found that taking the cap off the port, disassemble the front end and dip the nose in thinner and swishing it around cleans the port.

User avatar

Board Moderator
Posts: 5071
Joined: Tue Feb 24, 2004 7:00 pm
Location: central Ohio
Country:
USA
PostPosted: Sat Jul 06, 2019 10:41 am
Yeah, almost all of those "convertible" style cup guns suffer from that problem. I wonder if you could kind of redesign the plug so it had an internal silicone seal? We use different types of silicone and latex casting materials to replicate carvings. Some formulas are quite tough/durable and solvent proof. We have one high temp. formula that we can even cast metals in.....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



Settled In
Posts: 14
Joined: Sat Jun 29, 2019 9:07 am

Country:
USA
PostPosted: Sun Jul 07, 2019 6:32 pm
The way it looks to be designed, there's a smaller diameter port hole, then a larger diameter threaded hole in which an adapter screws into and butts up against the smaller hole sealing the OD of the adapter. Then a plug is screwed onto the adapter to seal the ID.

I suppose a Teflon disc could be made to fit in the port, then the adapter would screw up against it and seal the port and adapter. If that didn't work, then the adapter could be sealed on the end. I would most likely silver solder a short rod into the adapter. That would leave a shallow area that would probably clean out fairly easily. Either would be easily reversible if a suction feed cup is desired.

DarrelK - I believe you posted about using ice packs to cool the inlet air to the turbine. Have you tried cooling with a portable AC unit?

User avatar

Board Moderator
Posts: 5071
Joined: Tue Feb 24, 2004 7:00 pm
Location: central Ohio
Country:
USA
PostPosted: Sun Jul 07, 2019 10:12 pm
AC just doesn't seem to put out enough "cold" to keep the turbine blades cool. If the direct air to the turbine blades is kept cool the whole set-up will stay cool. What I like to do is shoot late at night when ambient temp.s drop into the high 60s low 70s and do the ice pack thing with my turbine just setting just outside my building. I also put a small desk top fan blowing on the ice packs directly at my turbine intake.....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



Settled In
Posts: 14
Joined: Sat Jun 29, 2019 9:07 am

Country:
USA
PostPosted: Mon Jul 08, 2019 6:13 pm
Being just south of Houston, not much chance of seeing 60s or low 70s this time of year. With the humidity here, I would be worried about going too cold and condensing water out of the air, which is why the AC unit seemed attractive.

It might be worth playing with a barrel of ice water and a radiator. Might be able to get it to thermosyphon so no pump needed. I would think ducting and a suitable fan would be needed.

Hmmm, might be an interesting project..................

Thanks for your input.

User avatar

Board Moderator
Posts: 5071
Joined: Tue Feb 24, 2004 7:00 pm
Location: central Ohio
Country:
USA
PostPosted: Mon Jul 08, 2019 10:49 pm
I can bring up a little more "food for thought" here.... back in Capspray's early days (they were absorbed by Wagner later on) they use to offer a special production turbine paint rig. This was at at time when you didn't have anything much past 2 stage motors. What they did was combine 2 of the 2 stage turbine motors on one chassis/platform (on wheels) thus creating the output of a 4 stage spray system....the problem, HEAT and a lot of it. What they ended up doing was building an air to air intercooler with it's own independent multi-speed thermo controlled fan. On that same chassis they also added a mini-compressor which would pressurize an on-board 2 gallon paint pot allowing the gun to just be a direct fluid feed with about 25 of fluid hose. The set-up worked pretty well for the times....it could handle much thicker liquids and I would say less heat was being generated in the air supply than even most modern 4 stage units. Soooooo....my point here is an air to air or ice-over-air kind of radiator could work but you would be battling somewhat the fact that there is a lot of CFM flowing through the system which may not have "time" to cool enough for a positive benefit. I would doubt that you could "crack" the air temp. enough that moisture would precipitate requiring a drain/catch can etc., but your going in a direction with this that hasn't been needed with the kind of temps we see around here....
Do keep something else in mind here.....the more "length" you add to your air hose going to your sprayer the more the air pressure will drop. Now that does not sound like a big deal and if we were talking compressed air it wouldn't be of that much concern. An average 4 stage turbine is only outputting 7 to 8 psi and even a 5 stage is probably in the 9 to 10 psi range. If you only knock down pressures a pound or two your 4 stage start performing like a 3 stage and your 5 stage drops to more like a 4 stage......again just some things to think about when you are playing with this stuff....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



Top Contributor
Posts: 4426
Joined: Tue Sep 16, 2008 1:17 pm
Location: Pahrump NV.
Country:
USA
PostPosted: Tue Jul 09, 2019 3:19 am
All you need to cool the compressed charge is a Place the Air can briefly expand.

Say your hose is 1 inch in dia. have it enter a chamber that's let say 8-12 inches in dia and 4 feet long then reduces back down to 1 inch. BAM! instant cooler air! An inter-cooler type expansion radiator with a fan would work best, coolers are cheap now days, water might wanna build up so you might want to design a Moisture collector and drain into it as well!

When Air is compressed it heats up, When it expands it cools. Even though its still under pressure in the chamber it still expands it still gives off Heat lots of it quickly.

physics class fellas
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

User avatar

Board Moderator
Posts: 5071
Joined: Tue Feb 24, 2004 7:00 pm
Location: central Ohio
Country:
USA
PostPosted: Tue Jul 09, 2019 1:53 pm
And, I wish I was a better student of air principles, ha, ha :lol: And I am familiar with that principle concerning compressed air however, I think it starts to fall apart somewhat because of the minimal amount of pressure involved and humongous amount of CFM that is being moved (60 to 130 cfm). One way we sort of work this out in our shop is to go from our hard-wired turbine in our storage area and plumb it with 2 inch pvc all the way to our furniture booth. Just doing that keeps our air hose temp.s around 90 or so all year long. That same turbine set-up on a short hose can hit nearly 130.....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



Settled In
Posts: 14
Joined: Sat Jun 29, 2019 9:07 am

Country:
USA
PostPosted: Tue Jul 09, 2019 7:01 pm
Well, I never took physics or chemistry. I did take calculus and Latin, not that I use either these days. Guess I took the wrong courses.

Anyway, seems like while the expansion chamber might cool, wouldn't you just heat back up going back into the small hose? I work at a chemical plant with lots of heat exchangers. Seems like if was that easy, we would have bunches of large diameter pipe in the plant instead, but we don't. I will talk to some engineers about it though.

I was thinking radiator as in car radiator because I figured it will flow lots of air and should transfer heat well. Seems to cool the engine coolant well and the air moving through is really hot. We have several fin fans at work where the engineers didn't want to pipe cooling water. Those also seem to work well.

This mainly was thinking out loud kind of stuff that might be worth looking into further.

User avatar

Board Moderator
Posts: 5071
Joined: Tue Feb 24, 2004 7:00 pm
Location: central Ohio
Country:
USA
PostPosted: Tue Jul 09, 2019 11:09 pm
Yeah, car radiator or large oil or transmission cooler would work also. The old Capspray units on those rigs I was talking about before looked like just a large oil cooler to me......
Get the thinking out loud thing completely...... :lol:
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!
Next

Return to Tools and Supplies

Who is online

Users browsing this forum: No registered users and 18 guests