2013



Results 1 to 17 of 17
  1. #1
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Mycom question and Manuals (Compound two stage)


    Dear all,
    1,My question is on MYCOM compound two-stage screw compressor 2520LSC. Why the oil heat rejection load almost does not vary with evaporating temperature?
    ET/CT Oil load
    -40/40C 132kw
    -45/40C 130.7KW
    -50/40C 130.3KW
    Is it reasonable?

    2,Anyone here has selection software of Mycom compressor and mycom screw compressor Installation & Operation manual, especially for Two-stage? Compound two-stage screw attract me a lot. Thanks in advance.

    Henry.



  2. #2
    Join Date
    Oct 2005
    Location
    Canada
    Posts
    33
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Henry

    A two stage compression system either a direct injection interstage cooling, or open flash interstage cooling, at the booster as the evaporating temperature goes down, say at constant discharge temperature as you have shown, many things are happening that are related. The compression ratio between the suction and discharge goes up, the discharge temperaure rocket up, as the compressor is doing more work, less mass flow rate to carry the heat, and the oil heat required to be rejected by the machine oil cooler is higher. The horsepower is down as the evaporating temperature goes down which help the oil heat rejection little bit; but also keep in mind that every refrigerant reacts differently to above scenarios.

    anything else copy me

    Camille Zabbal

  3. #3
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Thanks for your reply,Camille.
    Yes,Many things will happen when ET goes down. But this phenomen on mycom is totally different with on Bitzer hermetic screw compressor. I post the data of HSN8571-125(125HP,single stage,W/ Eco) here.
    ET/CT Oil heat load
    -35/38C 33.2kw
    -40/38c 35.8kw
    -45/38c 37.8kw
    -50/38c 39.2kw

    I don't intend to know every details in compressor theory,but wonder the reason of this difference and make sure the oil load data is correct for designing.

  4. #4
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    And wonder any friend has selection software of Mycom and IOM of Mycom screw compressor unit.This document will be very useful for me.

    Many thanks!

  5. #5
    Join Date
    Dec 2008
    Location
    Portugal
    Age
    38
    Posts
    1,014
    Rep Power
    8

    Re: Mycom question and Manuals (Compound two stage)

    Maybe, on the MYCOM WEBPAGE...
    To make progress is never good enough, I want to do better and better and better

  6. #6
    Join Date
    Nov 2004
    Location
    China
    Posts
    176
    Rep Power
    10

    Re: Mycom question and Manuals (Compound two stage)

    Henry,
    Contact Mayekawa office in Shanghai. They should have the manuals and their selection software CD. Tel: (86) 21-5116-8958.

  7. #7
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Many thanks for your information,Charlie.I will try,and BTW,we decide to start this project.

  8. #8
    Join Date
    Dec 2009
    Location
    Dubai
    Posts
    31
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Hi Henry
    My question to you is;
    How did you measure the oil heat rejection load at different ET? Is it from the specification manual or software?
    If we take it as you said, I think the oil cooler is over sized to be able to handle the oil heat rejection at different loads.
    I am totally agree with Camille and thanks to him for the clarification

  9. #9
    Join Date
    Dec 2007
    Location
    australia
    Posts
    1,595
    Rep Power
    15

    Re: Mycom question and Manuals (Compound two stage)

    henry ,
    The oil cooler heat load is correct according to the mycom programme ( for R22 ) .

    When you select oil cooler , select it for higher suction pressure to allow for a pull down .
    Also a bit of tube fouling if water cooled .
    R22 has a lot less heat rejection than say ammonia .
    Also a booster compressor if used seperately has small oil cooler load , so not much changes .

    If it was a Howden booster its completely different again to Mycom , but similar design !

    Bitzer has roller bearings which require very small amount of oil compared to Mycom whitemetel bearings .

  10. #10
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Many thanks all for helps!

    Yes,tabreed717,it's from selection software.
    Thanks you for your double-check,Ranger1.
    For oil cooler selection,I use ET setting +5K to calculate targeted oil load.

  11. #11
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Yes,Ranger1,different bearing types may lead to different oil mount. But i think it doesn't mean oil load must be different,because the oil load is determined by De-superheating load for refrigerant gas. Is it correct?
    thanks!
    right?

  12. #12
    Join Date
    Dec 2007
    Location
    australia
    Posts
    1,595
    Rep Power
    15

    Re: Mycom question and Manuals (Compound two stage)

    I think less oil through oil cooler less load .

    In the mycom programme total oil flow is for bearings etc only , as it does not require
    oil injection into rotors at all . Its using all oil to bearings to cool machine .

    Also compound mycom is 2 compressors not 1 as with Bitzer single stage economized .

    Do Bitzer make machines this big , or would you have to use several ?
    Last edited by RANGER1; 10-03-2010 at 01:01 AM.

  13. #13
    Join Date
    Oct 2005
    Location
    Canada
    Posts
    33
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Henry

    As I said the higher the compression ratio the more work the compressor has to do , more heat to be rejected from the oil
    At constant discharge and intermediate temperature for two stage compressor, as the suction drops down so is the horsepower so is the oil heat rejection.
    Now by changing the intermediate to higher temperature [constant discharge], we get higher tonnage, mind you it is more horsepower to produce that tonnage; but the compression ratio to the intermediate is less, so the oil heat rejection is down as the mass flow rate intermediate is less

    very unfortunate that the refrigeration engineer web will not allow more that 1mg file to be sent as I amde you sketches to understand the concept

    best regards
    Camille Zabbal

  14. #14
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Hi,Ranger1,Bitzer does not have the compressor as big as Mycom.


    Quote Originally Posted by RANGER1 View Post
    I think less oil through oil cooler less load .

    In the mycom programme total oil flow is for bearings etc only , as it does not require
    oil injection into rotors at all . Its using all oil to bearings to cool machine .

    Also compound mycom is 2 compressors not 1 as with Bitzer single stage economized .

    Do Bitzer make machines this big , or would you have to use several ?

  15. #15
    Join Date
    Mar 2007
    Location
    china
    Posts
    10
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Thanks,Camile.
    I fully agree with more oil heat rejection needed if higher compressoion ratio.
    While I am a little confusing on the results in case of increasing intermediate pressure. Yes oil load is less for high stage compression,but the oil load is more for low stage compression. Not sure how the total oil load will change.

    You could send email to me at shgzhang@hotmail.com at your convenience if you have some file to show me.

    Thanks again.
    Henry


    Quote Originally Posted by Camille View Post
    Henry

    As I said the higher the compression ratio the more work the compressor has to do , more heat to be rejected from the oil
    At constant discharge and intermediate temperature for two stage compressor, as the suction drops down so is the horsepower so is the oil heat rejection.
    Now by changing the intermediate to higher temperature [constant discharge], we get higher tonnage, mind you it is more horsepower to produce that tonnage; but the compression ratio to the intermediate is less, so the oil heat rejection is down as the mass flow rate intermediate is less

    very unfortunate that the refrigeration engineer web will not allow more that 1mg file to be sent as I amde you sketches to understand the concept

    best regards
    Camille Zabbal

  16. #16
    Join Date
    Dec 2010
    Location
    Missouri
    Posts
    5
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Did you get the manuals you needed? I have the 2520/3225 manual in electronic format.

  17. #17
    Join Date
    Oct 2007
    Location
    belgium
    Age
    36
    Posts
    11
    Rep Power
    0

    Re: Mycom question and Manuals (Compound two stage)

    Dear Henry,

    Where did you found your information ?
    ET/CT Oil load
    -40/40C 132kw
    -45/40C 130.7KW
    -50/40C 130.3KW

    Cause in my selection software taking in mind I selected the N2520LSC with random discharge port on Nh3, with open flash and oiltemp set at 50c I have following results.

    Oil load heat rejection calculated is at

    -40/40C = 197.9 Kw
    -45/40C = 185.7 Kw
    -50/40C = 175.7 Kw

    Kind regards,
    Harold



Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •