Scroll Compressors

  1. RonL

    RonL 907
    Gold Member

    After quite a bit of searching I have had little sucess finding specs or sources of buying just the scroll compressor head. Wiki and a few other sites have good animation that helped in the understanding of just how they work, and what makes them good for some applications.
    Most information has been very shallow, I would like to find information on, speed, volume, pressure, and specific size and mounting options, as well as possible dealers or outlets. Surplus is usually best for price, but there seems to be little supply on the market.

    If anyone can help, THANKS :smile:

    Ron
     
  2. jcsd
  3. RonL

    RonL 907
    Gold Member

    Maybe I should have used the words "air end".

    Again I don't want to have to buy one with a motor, or an A/C compressor unit.

    Thanks for any links or information.
     
  4. russ_watters

    Staff: Mentor

    You haven't really told us anything about what you are trying to do....

    What are you compressing? What voume and pressure do you want?
     
  5. Q_Goest

    Q_Goest 2,991
    Science Advisor
    Homework Helper
    Gold Member

    Hi RonL. I generally look for things like this at ThomasNet:
    http://www.thomasnet.com/
    Be prepared to make some phone calls too. You can do a search but with the more complex things such as compressors, you're better off calling and talking to a sales person live.

    Thomas Register used to have a line of green books that looked like a set of encyclopedias. They'd come out once a year and cost a small fortune. Now with the internet, that line of books has gone away and replaced by the ThomasNet web site. There are others like it such as GlobalSpec.com but I'm kinda partial.
     
  6. FredGarvin

    FredGarvin 5,087
    Science Advisor

    Whoa. I completely forgot about the old Thomas books.
     
  7. Q_Goest

    Q_Goest 2,991
    Science Advisor
    Homework Helper
    Gold Member

    Yea, the Thomas books were like the internet on paper. They were so expensive, and so valuable, that when some department bought a new set, the old ones could be auctioned off to subsidize the new set.

    Alas, they've now gone the way of the slide rule.

    I'm not complaining though, mind ya. :tongue2:
     
  8. RonL

    RonL 907
    Gold Member

    Thanks Russ, Fred, Q,

    I have seen scroll compressors in books in the past, but the mind could not quite grasp the operation, a link in some other thread took me to wiki, where they showed an animation of operation, the mention of no need for valves or lubrication in some cases, gave me reason to look at these compressors opposed to vane units.

    I have two vane motors that are rated at just under 5 HP, RPM 3,000 and if I remember correctly 14 CFM@ 100 PSI. These require some method of lubrication, which poses some unknowns for me. These motors are quite small and lite, when compared to most other things in the 5HP range. I would like scroll units somewhat like these.

    As for the Thomas directories, I do have two old sets that I picked up from the main branch of the Austin library many years ago (they were updating, and selling off old books) like PF they take up a lot of time.:biggrin: They always seem to be behind something, and too much trouble to dig out. Their best service so far has been holding up 4 other shelf boards.:rolleyes:

    This is still in relation to an energy system that I am working on, both In my mind and physically. Due to the size of my system tanks (largest is 250 Gallon) my bobcat has had to give up it's seat on the trailer:rofl:.

    I'm keeping most of this separate from my real goal of having a propane based heat absorption unit. My knowledge is building thanks to PF, just not at the pace I had hoped for, I'm back home for a while and hope to get caught up, and back on track as soon as I can figure out where the track is.:confused:

    Russ, as for the PM on the lead acid battery, that is still on the back burner and I have the components to work on a prototype, looks like prep work for father's day has taken first place, so my questions will come some time after that.

    Thanks All

    Ron
     
    Last edited: May 12, 2009
  9. RonL

    RonL 907
    Gold Member

    To answer a little of this question, the compression of two materials, one air and the other propane vapor, the propane is a closed system and enclosed in a tank. Air is drawn into the same tank and compressed but kept isolated from the propane, and then exhausted at a colder temperature. (100 F degrees in, and 33 F out) air flow volume determines KW output.

    The working of this design will focus on a single power shaft, which involves 4 or more (vane or scroll) units plus a generator that serves as both a drive motor if needed at any time, and a method of extracting power, which is needed to equal out the change in temperature of the air that flows through the system.
    I would like high pressure which would reduce size, but around 100 psi keeps things at a safer level.

    The basis that I'm working on is, all mechanical work takes place inside the cold reservior, which moves heat of compression and frictional heat into a cold propane liquid, which in turn raises propane gas pressure (waste heat is always recycled).

    The use of two drive units (air and propane) and two scavaging units with a length of tubing and check valves of proper pressure ratings between them will assure that pressures stay at proper levels.

    An insulated inner tank will serve the need of two levels of pressure and temperature in the propane portion of the system.

    Again as said before in another thread, the most important goal of this design is lots of cold air, the electrical output keeps the system from overheating.
    I think whats different here is the intake and discharge are interacting with just one reservior. It's easy to get lost inside and hard for me to put into words, but it is kinda like the dog that chases his tail and never catches it.:smile:
     
  10. RonL

    RonL 907
    Gold Member

    I found a little information on a base mount unit that is v belt driven, all data is about the same as the vane motor, but at 49 pounds it is almost three times as heavy as the same 5 hp vane motor and almost twice as large.
    Having the option of a dual output shaft on the vane motors will let me set them in a straight line, and have a more compact configuration.

    Thanks for the help:smile:
     
  11. RonL

    RonL 907
    Gold Member

    Well my AC friend finally delivered two 5 ton rated scroll compressors, they appear to be small in diameter(which is good) and are quite heavy, hopefully it is in the shell and motor weight. I will need to disect them carefully, in order to use the portion of the shell they are mounted in. I'm trying to decide between using a disc grinder (messy and more pron to be dangerous) or a metal cutting band saw (will have to build a jig and rotate the shell two or three times) much slower.

    And then there is the smokey cutting torch.:uhh::frown:

    Have any of you guy's done this before?

    Anyone with any information please speak up.:smile:

    It always amazes me how many times threads are viewed and no one comments in any way.
    I'm not just talking about my post and threads.

    Ron
     
  12. RonL

    RonL 907
    Gold Member

    Some good news, I found what seems to be the main market for scroll compressors, the two that I have are Copeland refrigeration units (57,000 and 61,000 BTU) the spec tag says the rating for pressure is 20 bars, this just might compensate for the extra weight.

    I have decided to set up a lazy suzan style turntable on my work bench and build a solid mount for an angle grinder, then seperate the base from the shell, just above the internal motor mount, which will allow the motor to drop out. Depending on my design options the two shells will be clamped togeather forming a dual air end unit.

    As best I can tell the coupling between the motor shaft and the compressor unit appear to be a slip fit, something like a Lovejoy flex coupler.

    After this weekend maybe I can put some time in on this project.:smile:

    Ron
     
  13. Tell me how it works out! And please post pictures!
     
  14. RonL

    RonL 907
    Gold Member

    Thanks, I will :smile:
     
  15. RonL

    RonL 907
    Gold Member

    I have looked at this before and sometimes things just come into focus.

    http://en.wikipedia.org/wiki/Maxwell's_demon

    Maybe if I'm wrong someone can say why.

    If one scrolls down the page to experimental work by David Leigh, it seems that his work is much like what I'm building, where two gases exchange energy and the generator serves the demon function. He used light, I'm drawing heat from the atmosphere.

    I'm not sure, based on very little response, that anyone really understands what is described above in my system. The view count has been pretty high. (Imo)

    Time is flying and I'm missing my golden opportunity, the temperatures here are triple digets (103 yesterday) Too hot to work outside.:yuck:
     
  16. Scroll compressors can go up to 7-8 bar (atm) so one might be enough. They have a very good m3/min depending on size and can work even without lubrication ( bit more expensive).

    If the sole purpose is cold air then the propane seems useless. Use water instead to absorb the heat.
     
  17. RonL

    RonL 907
    Gold Member

    The sole purpose is not just cold air, the propane and electricity is how such an extreme difference of high and low temperature can be defined within a single cold reservior. The power and pressure differences are worked through the air motors as both, compression and expansion devices.

    My thinking might be flawed as to which is best in the long run, I shy away from water because of ice, and the fact that in steam range (might be best) heat tends to move out of the system.

    Propane gives the added value of drawing in heat from the atmosphere as well as absorbing the waste heat of compression, when in it's low temp state.
    IF NEEDED, it can contribute to the heat value of the system, as it is a combustion type fuel.

    The fact that so many forms of stored energy can be designed inside the cold reservoir, steam could in fact come into play in the system as an intermediate power provider. The overall goal is to pull air in at a higher temp and discharge it at a much colder state.

    The fact that this refocus of waste heat (of compression) into a driving power, lets the final facts come out to three things,

    A. BTU's removed from total air flow.
    B. Water drop out from condensation.
    C. Electrical Wattage (output) equal to sum of BTU removed from air.

    Ron

    P.S. The copeland specs on the side of the compressor states a 20 bar max pressure (it is a scroll)
     
  18. RonL - Did you have any luck locating a scroll compressor (only) unit? I have a similar project? If so, can you point out the solution for me?

    Big thanks in advance,
     
  19. RonL

    RonL 907
    Gold Member

    So many things change my focus with the greatest of ease, so no I have not gone beyond where I was in post #11.
    The big holdup.....??? I simply can't make a decision about how and exactly where to cut the housings so that I can still use the end sections and not ruin the critical alignment of the scroll unit.
    Work and other factors have been the main cause of the project setting in a paused condition, but it is still in the plan for what I want to do.

    Thanks for asking, it will be a good motivator.

    Ron

    PS in searching the net I did see some units in designs that mount solid and a motor is added using belt and pully.
    These were physically the wrong shape and size for what I want to do.
     
    Last edited: Aug 17, 2010
  20. Back when Trane had engineers in the USA (now in India), I used to work there. Being in the environment, gave me some insider knowledge on compressors, including the scroll. All compressors need predigious lubrication. In the reciprical types, the oil settles to the bottom of the compressor housing and gets drawn up through an angled hole in the shaft.
    I'm not certain how the oil gets drawn into the scrolls working area, BUT it's absolutely essential that it's soaking in oil. The oil forms the gas-tight seal and, it gets between the metal peices, preventing them from rubbing.
    In and AC/Heat pump, oil mist is continually leaving the compressor and getting mixed up with the refrigerant, but the cycle has a preference for bringing oil back to the compressor, so it doesn't dry out.
    If you reverse the process and use the compressor as a generator (which a scroll can do for awhile - if properly modified) then the oil will tend to settle outside the compressor, and eventually you run dry. Shortly after that, your scroll self detructs (had experience with this during R&D).
    Now vacuum people have another type of scroll that runs dry. It uses graphite surfaces that wear together and shortly need to be replaced. These puff microscopic carbon powder instead of the oil you see with most vacuum pumps.
     
  21. RonL

    RonL 907
    Gold Member

    Thanks Mike,
    Some of that kind of information is so hard to find and dig out, I did find a little about the dry running units and the information sounded like the longer they ran the better the seal, which is what you said, but no indication about how quick repair or replacement have to happen.

    You have read this thread and maybe others, in a closed design I see no real problem using propane as a refrigerant, do you know of a lubricant that would work well and not dilute too much? I'm not sure how, but I think distribution and recovery are things that can be designed for, without too much effort. Any advise or thoughts?

    Thanks
    Ron
     
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