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  1. #1
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    Sizing finn and tube evaporator



    Dear All,
    I selected Danfoss SC21G compressor for a refrigeration application. At 0 Deg. C evaporating temeperature, it will give 1268 Watts cooling capacity, it is sufficient for my application. The refrigerated space temperature required is +5 Deg C. As per compressor catalogue, the displace ment volume is 20.95 cubic CM, Maximum refrigerant charge is 1300g and Free gas voulme in compressor is 1460 cubic CM. Suction and discharge connector ID are 10.2 and 6.2 mm repectively. From these data, how I will size a (forced) air cooled Finn and tube evaporator? (the guy who makes evporator coil need only physical size, not the capacity required). Fan details: 97 cfm, Power: 22 Watts. Expansion device: capillary tube.I have to design a custom fabricated evaporator for this cooler.The material for evaporator is copper tube and aluminium fins. Fin spacing: 5 fins per inch. Can any one help me, please?
    With thanks in advance,
    Cheers,
    Rayin



  2. #2
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    Re: Sizing finn and tube evaporator

    it is not your job to design evaporators. its the manufacturer.
    My best advice to you is to check evaporators manufacturers web sites such as LU-VE and ALFA-LAVAL, they offer software to choose evaporator size, air flow, fin spacing, etc, that will match your requirements.

  3. #3
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    Re: Sizing finn and tube evaporator

    Dear Chemi-cool,
    Thank you for your quick reply. The ready to fix type evaporator can't fit in this case, as the space is narrow. How do those evaporator manufactures calculate the coil size, for a specific cooling requirement? Any idea?
    Thanks again

  4. #4
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    Re: Sizing finn and tube evaporator

    They calculate it first with own made software and they then test it in a real life situation in a caloriechamber.
    The capacity depends on tube and fin material, row arrangement, tube dimensions, airflow through the coi,...
    What are you restrictions in dimensions?
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  5. #5
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    Re: Sizing finn and tube evaporator

    Dear Peter-1
    Thanks for your reply. My cooler inner depth is only 350 mm. What is it the EVAP-COND software for? Can it use to design evaporator coils?
    Thanks again,
    With regards
    Rayin

  6. #6
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    Re: Sizing finn and tube evaporator

    And available height?
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  7. #7
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    Re: Sizing finn and tube evaporator

    Dear Peter_1,
    It is 2.2 M (2200 mm), all sides glass. The top is in insulated, stainless steel fabrication, 50 mm tbick and the evaporator has to hang it there.
    From the displacement volume and rpm of motor, we can calculate the refrigerant amount pumped per unit time. And from properties of refrigerant chart, the specific voulme of the gas (R134a) at a given temperature and presure also can calculate. Using these datas, can we size the length of evaporator coil? In the "Modern Refrigeration & Air Condiotioning" (by Andrew D. Althouse, Carl H. Turnquist & Alfred F. Bracciano) page no. 655 & 656 explains the metod to find out the area of finn and tube evaporator. But it doesn't consider the finn efficiency.
    Your valuable comments anticipated.
    With thanks and regards
    Rayin

  8. #8
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    Re: Sizing finn and tube evaporator

    My compressor has a displacement of 21.6 cm3 per revolution, is 12,000 BTU, for air conditioning, and I need to know the minimum tube length it needs to operate without the compressor overheating. Any ideas?

    I guess it is somewhat similar to the Danfoss.
    Visit http://www.kompulsa.com/ for technology news, reviews, and more. Twitter: Kompulsa.

  9. #9
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    Re: Sizing finn and tube evaporator

    Dear All,
    Nobody here with experience in evaporator coil design? If we know the physical size of condnsor (tube length, dia meterm number of fins etc), will it help in fabricating the evaporator coil? Ther is any rule of thumb between the size of evaporator and condensor? Any feed back is highly appreciated,
    With thanks and regards,
    Rayin

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