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  1. #51
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    Re: Compressor as Expander for power (Rankine Cycle)



    190kW shaft output power from the expander is very large. Working on a isentropic efficency of around 0.6 ish, enthalpy change will be around 66kJ/kg and therefor mass flow will be around 2.88kg/s giving a volume flow at the expander inlet of around 2.88cum/s and around 26.5cum/s at the outlet. With these sorts of flow you have no option but to go for turbo compressors/expanders and large ones as well.



  2. #52
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    Re: Compressor as Expander for power (Rankine Cycle)

    Too funny this was an email I was reading the other day when we had a request for such a project.

    We have a screw compressor designed as a steam expander roughly generating 100-200 kW with 250-275 psi steam.

    I have just started my research on the unit now so I have limited answers but have not problem digging more answers for you if need be.

    Iceman
    Refrigeration is not just cool, it is my life.

  3. #53
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    Re: Compressor as Expander for power (Rankine Cycle)

    Hi everyone.

    I am studying and developing a ORC with 1 kWe as output, using a car air conditioning scroll compressor as expander.

    How can I work out the values of flow rate needed, knowing the inlet and outlet pressure??

    Thank you.

  4. #54
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    Re: Compressor as Expander for power (Rankine Cycle)

    the simple way, roughly, ET?, CT?, refrigerant? then you get know EP, CP, depending on ET, efficiency around 10%; you get the flow. You can search online a thermodynamic software/formular for that calculation

  5. #55
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    Re: Compressor as Expander for power (Rankine Cycle)

    forget the compressor idea.
    You will need something running on steam like a steamengine or a turbine.
    water will boil at 85 degrees when the pressure is lowered a little.

    Your water from the engine under pressure can be relieved into a expanding vessel, the liquid pumped back to motor and the vapour is used in a steamengine. The vapour is condensed and also pumped back to the motor.
    this way no need for heatexchangers so the efficiency is high.

    I have a central heating working with a stirling engine, that is another way to produce power.
    computer shooter
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  6. #56
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    Re: Compressor as Expander for power (Rankine Cycle)

    What about using a piston powered fridge compressor instead of a turbine? The expanding gas can increase cylinder pressure and force the piston down, and then it would reciprocate and do the same again, causing rotation.

  7. #57
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    Re: Compressor as Expander for power (Rankine Cycle)

    Can do but have to modify its valves controlled by crankshaft like an old train engine

  8. #58
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    Re: Compressor as Expander for power (Rankine Cycle)

    Yes, the flap valves must be reversed. Basicly the valve plate must be installed upside down.

  9. #59
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    Re: Compressor as Expander for power (Rankine Cycle)

    you all have no idea how a steamengine is working.
    read the book
    reversing will not help.
    computer shooter
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  10. #60
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    Re: Compressor as Expander for power (Rankine Cycle)

    I don't know who you're talking to, but I was referring to a reciprocating piston semihermetic compressor for refrigeration. Not a steam engine.

  11. #61
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    Re: Compressor as Expander for power (Rankine Cycle)

    so you say turn the flaps, the piston will go down at that moment, and how do you think to close the flaps and let the piston go up again ????
    you are really missing some basic here.
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  12. #62
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    Re: Compressor as Expander for power (Rankine Cycle)

    Quote Originally Posted by shooter View Post
    so you say turn the flaps, the piston will go down at that moment, and how do you think to close the flaps and let the piston go up again ????
    you are really missing some basic here.
    Yes, you're right. My mistake. The intake and discharge must be commanded with a gear train, not a flap.

  13. #63
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    Re: Compressor as Expander for power (Rankine Cycle)

    Ya, He's talking the one who's talking about recip expander (recip steam engine) means no idea on steam engine history, look back on this with engineer brain. "Bitter medicines fix remedies" (Vietnamese proverb)

  14. #64
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    Re: Compressor as Expander for power (Rankine Cycle)

    All,

    I ran across this thread doing some research online. I happen to work at a company called Air Squared, Inc. that manufactures and designs scroll expanders. I think someone else mentioned us in an earlier comment. I believe we are one of the only companies that offers them.

    Because of the all the interest surrounding our scroll expanders for waste heat recovery, we actually put our 1 kW and 5 kW scroll expanders into full production. The expander is in use in a numer of ORC applications (mostly university projects so far). The test data has been great.

    Anyway, thought I would share the info. You can find more on our site at htto://airsquared.com. Hope this helps and good luck.

  15. #65
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    Re: Compressor as Expander for power (Rankine Cycle)

    I just got cad plans for a tesla turbine has anyone thought of that . Cheap to build. Also has anyone thought of using the cold gases like hydrogen which they use to cold the windings on large generators at power plant. My first orc will use co2. Any thoughts on that let me know please

  16. #66
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    Re: Compressor as Expander for power (Rankine Cycle)

    A question and another idea. Why in orc do most want to use open or closed loop steam . Isn't there a lot more wasted heat then closed loop refrigerant based system . Yes I know the pressures get very high but one could make the system stronger aand gain the high efficiency . Now the idea open loop steam orc . One could make hydrogen easily with the wasted steam to store for use in a furnas at night instead of using batteries. Tell me your thoughts on that.

  17. #67
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    Re: Compressor as Expander for power (Rankine Cycle)

    Hello Everyone,

    I am working on building a 1.5kW electrical output ORC system. The heat input is around 10kW.
    A good source for small scale expanders is Infinity Turbine. They make units from 1kW, 10kW to over 100kW.

    Almost ready to start assembling the circuit. Does anyone know where I can purchase small quantities of R245fa refrigerant (<5kg)?

  18. #68
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    Re: Compressor as Expander for power (Rankine Cycle)

    Hello Tanner,

    I am also building a 1.5kW electrical output ORC system. If I was to use R245fa refrigerant, I figure I will need a mass flow rate of 0.04kg/s to achieve about 1kW net electrical output. This is with the evaporator working at 1700kPa absolute and the condenser working at 287kPa absolute.

    I can look up some pressure-enthalpy diagrams if you need some info. I chose to use custom expanders made by Infinity Turbine which are hermetically sealed and do not require oil lubrication. More expensive, but better efficiency then converting Copeland scrolls.

  19. #69
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    Re: Compressor as Expander for power (Rankine Cycle)

    I guess the best technology is the compressor working as expander
    Last edited by rcarlitos99; 07-03-2012 at 06:56 PM.

  20. #70
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    Re: Compressor as Expander for power (Rankine Cycle)

    Have you seen the ORC from ENERBASQUE (http://www.enerbasque.com/en/orc.html). It is based on compressor working as expander. They have a 25 KWe unit and I think, also, it is possible to subcontract his services as ORC consultants or order and stand-alone expander for your project.
    Our company has worked with them in this area and we are really happy with their services. They are really experts in this ORC world and they know the most appropiate technology and design options for each project.
    Just an option for the projects I have seen here. They are really interesting!!

  21. #71
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    Re: Compressor as Expander for power (Rankine Cycle)

    Hello
    I think that a small steam turbine is indicated that much of a screw compressor ..

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