Results 1 to 10 of 10
  1. #1
    Join Date
    May 2006
    Location
    India
    Age
    68
    Posts
    400
    Rep Power
    12

    Air cooled condenser design



    Hi ,
    how do we work out the heat exchange capacity of the copper tubes used in an air-cooled condenser with 8 fpi, fins per inch ( aluminum ) ???
    Or how do we decide the length of copper tube say 3/8 inch diam for a 30 kw air cooled condenser with 15 deg f td , ambient 40 deg c ???
    I eed some input to work on condenser design ..



  2. #2
    Join Date
    Sep 2003
    Location
    ISRAEL
    Age
    65
    Posts
    4,109
    Rep Power
    37

    Re: Air cooled condenser design

    Designers use some software.
    Basically its the cooling capacity+compressor input+20% or more, depends on the ambient.

  3. #3
    hassanfrag's Avatar
    hassanfrag Guest

    Re: Air cooled condenser design

    CONDENSER SELECTION
    Capacity for air-cooled condensers are based on Total Heat of Rejection (THR)
    at the condenser. Total heat of rejection is equal to net refrigeration at the
    evaporator (compressor capacity) plus the energy input into the refrigerant
    by the compressor (heat of compression). The heat of compression will
    vary depending on the compressor manufacturer, type of compressor
    and the operating conditions of the compressor. Whenever possible, it is
    recommended that you obtain the heat of compression value from the
    compressor manufacturer.
    If this is not available, the THR can be estimated using the following formula:
    THR = (Compressor Capacity) * (Heat of Compression Factor, Tables 1 & 2)
    Table 1 contains heat of compression factors for suction cooled compressors
    and Table 2 contains factors for open drive compressors. For refrigeration
    systems beyond the range of Tables 1 and 2, use the following equations to
    estimate THR:
    Open Compressors:
    THR = Compressor Capacity (BTUH) + (2545) * (Break Horsepower, BHP)
    Suction Cooled Compressors:
    THR = Compressor Capacity (BTUH) + (3413 * KW)
    The compressor capacity is affected by its altitude. If the condenser location
    is above sea level, an additional correction is required to the THR, as follows:
    THR (altitude) = THR * altitude Correction Factor, Table 3
    Selection Example
    Compressor capacity: 270,000 BTUH
    Evaporator temperature: +25 F
    Condensing temperature: 110 F
    Ambient temperature 95 F
    Refrigerant: R-404A
    Compressor type: Semi-hermetic, suction cooled
    Condenser type: N RG
    Condenser altitude: 1,000 feet
    Step 1: Estimate Condenser THR
    From Table 1 for suction cooled compressors, at +25 F suction and 115 F
    condensing temperature, select a heat of compressor factor of 1.335.
    THR = Compressor Capacity * Heat of Compression Factor
    = 270,000 * 1.335
    = 360,450
    Step 2: Correct for Altitude
    From Table 3 obtain an altitude correction factor of 1.02 for 1,000 feet.
    THR = THR (from step 1) * Altitude Correction Factor (design)
    = 360,450 * 1.02
    = 367,659
    Step 3: Calculate Design Condenser T.D.
    Design Condenser T.D. = Condensing Temp — Ambient Temp
    = 110F - 95
    = 15 T.D.
    Step 4: Condenser Selection
    Condenser capacitiesare located on page 6. These capacities are given in
    MBH/TD. Convert the THR calculated in step 2 to MBH/TD by dividing
    by 1,000 to get THR in MBH. Then divide the THR by the design TD to get
    MBH/TD.
    THR (MBH) = 367,659 / 1,000 = 367.7
    THR (MBH/TD) = 367.7 / 15 = 24.5
    Locate the capacity column and read down until you locate a value equal to or
    just larger than 24.5. This value is 27.0. Read horizontally to the left to obtain a
    condenser model of NRGD04A027
    Step 5: Calculate Actual T.D. and Condensing Temperature
    The actual condenser T.D. can be calculated by dividing the design THR by
    the condenser rating.
    Actual T.D. = THR (Design) / (Rating @ 1 T.D.)
    = 367.7 / 27.0
    = 13.6F. T.D.
    The actual condensing temperature is the actual T.D. plus the ambient
    temperature.
    Actual Condensing Temperature = (Actual T.D.) + (Ambient)
    = 13.6 + 95
    = 108.6F.
    Altitude Correction Factor
    0 1
    1,000 1.02
    2,000 1.05
    3,000 1.07
    4,000 1.1
    5,000 1.12
    6,000 1.15
    7,000 1.17
    Table 1. Heat of Compression Factor for Suction Cooled Compressors.
    Table 2. Heat of Compression Factor for Open Drive Compressors.
    Table 3. Altitude Correction Factors.
    Evaporator Condensing Temperature F
    Temp. F 90 100 110 120 130 140
    -30 1.37 1.42 1.47 — — —
    -20 1.33 1.37 1.42 1.47 — —
    -10 1.28 1.32 1.37 1.42 1.47 —
    0 1.24 1.28 1.32 1.37 1.41 1.47
    5 1.23 1.26 1.3 1.35 1.39 1.45
    10 1.21 1.24 1.28 1.32 1.36 1.42
    15 1.19 1.22 1.26 1.3 1.34 1.4
    20 1.17 1.2 1.24 1.28 1.32 1.37
    25 1.16 1.19 1.22 1.26 1.3 1.35
    30 1.14 1.17 1.2 1.24 1.27 1.32
    40 1.12 1.15 1.17 1.2 1.23 1.28
    50 1.09 1.12 1.14 1.17 1.2 1.24
    Suction
    Temp. F
    Condensing Temperature F
    90 100 110 120 130
    -40 1.56 1.63 1.72 1.81 1.94
    -30 1.49 1.55 1.62 1.7 1.8
    -20 1.43 1.49 1.55 1.62 1.7
    -10 1.38 1.43 1.49 1.55 1.63
    0 1.34 1.38 1.43 1.49 1.56
    5 1.31 1.36 1.41 1.48 1.55
    10 1.29 1.34 1.39 1.44 1.52
    15 1.26 1.31 1.36 1.41 1.48
    20 1.24 1.28 1.33 1.38 1.44
    25 1.22 1.26 1.31 1.36 1.42
    30 1.2 1.24 1.28 1.33 1.39
    40 1.17 1.2 1.24 1.28 1.33
    50 1.13 1.16 1.2 1.24 1.28
    Note: These units are optimized for operation at or below 15 T.D.
    Operation above 15 T.D. may result in excessive pressure drop.
    Table 4. Correction Factors.
    Correction Factor Capactiy Refrigerant Charge
    R-404A 1.00 1.00
    R-22 1.02 1.09
    R-410A 1.02 1.07
    R-507 1.00 1.00
    50 Hz Power Supply 1.00 --

  4. #4
    Brian_UK's Avatar
    Brian_UK is online now Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
    Join Date
    Mar 2001
    Location
    Dorset
    Age
    69
    Posts
    10,444
    Rep Power
    50

    Re: Air cooled condenser design

    Hassanfrag,

    Good copy from some unidentified publication but does not answer the question posed by DD Koranne.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015
    Please support http://the100project.net/Home

  5. #5
    Join Date
    May 2007
    Location
    Auckland
    Age
    67
    Posts
    3,362
    Rep Power
    31

    Re: Air cooled condenser design

    All condenser manufacturers will specify performance versus highest ambient dry bulb condition, and I take that with a grain of salt, I prefer evap/condensers and take advantage of the wet bulb effect. all dependent on refrigerant applied and max discharge temps applicable

  6. #6
    Join Date
    Dec 2011
    Location
    China
    Age
    30
    Posts
    1
    Rep Power
    0

    Re: Air cooled condenser design

    How professional it is!

  7. #7
    Join Date
    Jul 2001
    Location
    Sydney, Australia
    Posts
    764
    Rep Power
    19

    Re: Air cooled condenser design

    The question is about air cooled condenser DESIGN, not selection.

    I will have to look through some of my notes to list the exact process, I would suggest it is easier to approach a coil manufacturing company who do this stuff all the time. They will usually use a program to work out the required coil configuration and airflow, it can be done by hand but at the end of the day you still need to order it from a coil company so you may as well use their expertise in design as well.
    ...and she said "give it to me you big fridgie"

  8. #8
    Join Date
    Mar 2009
    Location
    KZN, South Africa
    Age
    57
    Posts
    2,212
    Rep Power
    13

    Re: Air cooled condenser design

    http://www.coolit.co.za/coilsim/index.htm

    T
    here are some excellent software packages on this site. I use them for industrial & RHVAC design. The license prices are very reasonable. Send my regards to Bruce.
    Engineering Specialist - Cuprobraze, Nocolok, CD Technology
    Rarefied Technologies ( SE Asia )

  9. #9
    Join Date
    May 2006
    Location
    India
    Age
    68
    Posts
    400
    Rep Power
    12

    Re: Air cooled condenser design

    Hi brian ,
    yes that is right . I have software which calculates the total heat rejection in condenser . But when it comes to buy a condenser , manufacturers expect me to specify the tube diameter for cond coil ,size of face area , total tube length , and number of rows etc which constitutes the manufacturing data.

    They can fabricate one based on the info but cannot design a cond based on the purely load data of the condenser ......... All in all i need to understand how to work out the tube length and diam etc and feed the cond manufacturer .............

  10. #10
    Join Date
    May 2006
    Location
    India
    Age
    68
    Posts
    400
    Rep Power
    12

    Re: Air cooled condenser design

    And the same applies to water cooled condenser

Posting Permissions

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