Results 1 to 9 of 9
  1. #1
    Join Date
    Apr 2009
    Location
    US
    Age
    36
    Posts
    5
    Rep Power
    0

    Student Project (Cascade Refrigeration System)



    Hi,

    I am working on a project to optimize the evaporating temperatures, superheat and subcooling on a 2 stage cascade refrigeration cycle using R404a and R744 (CO2). I've setup everything in EES but I have a few concerns regarding the solution I'm getting:

    My ltc evap temp is -45C and im testing 10C superheat. When I ran the equations, I got a temperature of 58C at the ltc compressor outlet at almost 4 MPa, which seems a bit high to me, but I really dont know for sure.

    I tried to parametrically plot my COP vs. the htc evap temperature, and the COP just keeps going up without bound. I was expecting to see an inverse parabola, but the COP never decreases.

    If anyone has any suggestions for me please let me know. Thanks!

    David



  2. #2
    Join Date
    Mar 2006
    Location
    Merate (LC) - Italy
    Age
    52
    Posts
    2,554
    Rep Power
    24

    Re: Student Project (Cascade Refrigeration System)

    I'm not sure what exactly you input in the calculation, but I'm pretty confident that 58°C at compressor discharge is quite normal, provided the condensing temperature is subcritical (let's say around 50K discharge superheat)

  3. #3
    Join Date
    Apr 2009
    Location
    US
    Age
    36
    Posts
    5
    Rep Power
    0

    Re: Student Project (Cascade Refrigeration System)

    ok, thats good to know, i wasn't sure.

    But now, my problem is that when I plot the COP vs. the cascade temp for a specific set of design conditions, the COP just increases almost linearly without a limit. Any ideas?

  4. #4
    Join Date
    Mar 2006
    Location
    Merate (LC) - Italy
    Age
    52
    Posts
    2,554
    Rep Power
    24

    Re: Student Project (Cascade Refrigeration System)

    That's also normal. As the evap temperature increases, the COP increases as much, and the reason is the higher mass flow at suction together with a better volumetric efficiency. Please note that the evap temperature in a real case scenario is bound to the physical constraint of the testing setup

  5. #5
    tctarunchauhan's Avatar
    tctarunchauhan Guest

    Re: Student Project (Cascade Refrigeration System)

    hey buddy may i have ur analysis on EES..??? if u dont have any prob plz send it to me....i thnk i m working on somewhat similar project so i need ur help

  6. #6
    rockon605's Avatar
    rockon605 Guest

    Re: Student Project (Cascade Refrigeration System)

    is there any way to plot property curve (say T-s diagram) for two different fluids on same graph, i.e. overlaying one's property plot over another in 'EES'?
    if anyone knows plz reply.
    actually i need combined T-s diagram for ammonia and ethane on one plot.

  7. #7
    Join Date
    Mar 2009
    Location
    KZN, South Africa
    Age
    63
    Posts
    2,212
    Rep Power
    20

    Re: Student Project (Cascade Refrigeration System)

    Coolpack can assist. It's a free download based on the EES platform.
    Engineering Specialist - Cuprobraze, Nocolok, CD Technology
    Rarefied Technologies ( SE Asia )

  8. #8
    pal.of.pinaki's Avatar
    pal.of.pinaki Guest

    Unhappy Re: Student Project (Cascade Refrigeration System)

    Hey guys,

    I am also working on a project based on CO2 cascade refrigeration systems......if anybody can send me the code pertaining to the optimisation of cascade system in terms of intermediate temp.(IT) and overlap temp(DT) I would be highly thankful.

  9. #9
    jonbonraki's Avatar
    jonbonraki Guest

    Re: Student Project (Cascade Refrigeration System)

    I am also working on a project based on CO2 cascade refrigeration systems......if anybody can send me the code pertaining to the optimisation of cascade system in terms of temp(DT) .

Similar Threads

  1. Replies: 9
    Last Post: 30-11-2009, 11:08 AM
  2. Single stage refrigeration system optimizing diagram
    By autt in forum System Optimization
    Replies: 34
    Last Post: 03-12-2008, 04:13 PM
  3. cascade system
    By sagittarius in forum Industrial
    Replies: 3
    Last Post: 14-03-2008, 12:50 PM
  4. Help for a university refrigeration project
    By uni_student in forum Industrial
    Replies: 39
    Last Post: 04-03-2008, 03:43 PM
  5. project of refrigeration plant
    By gesi in forum Fundamentals
    Replies: 5
    Last Post: 12-06-2006, 07:13 AM

Posting Permissions

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