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Condenser & Evaporator

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    Design o f Air coo led evapo rator manual ly

    Air cooling evaporators for cold rooms, blast freezers, air-conditioning, etc., will have

    finned pipe coils in all but very small coolers, there will be fans to blow the air over the

    coil. Construction materials will be the same as for air-cooled condensers. Aluminumfins on copper tube are the most common for the halocarbons, with stainless steel or

    aluminum tube for ammonia. Frost or condensed water will form on the fin surface and

    must be drained away. To permit this, fins will be vertical and the air flow horizontal,

    with a drain tray provided under. The size of the tube will be such that the velocity of

    the boiling fluid within it will cause turbulence to promote heat transfer. Tube

    diameters will vary from 9 mm to 32 mm, according to the size of coil. Fin spacing

    will be a compromise between compactness (and cost) and the tendency for the spaces

    to block with condensed moisture or frost. Spacings will vary from 2 mm on a compact

    air-conditioner to 12 mm on a low-temperature cold-room coil.

    We will design manually and by Techinsolve software

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    Evaporator Design :

    From the psychrometric chart:

    Inlet condition:

    dbta in=380c & wbta in=33

    0cha in=114.15kj/kg & Wa 1=0.01585 kgw/kga

    TDP=21.20c

    Outlet condition:

    C.S.H.F=0.40 & RH=100%ha out=90 kj/kg

    Cooling load:

    Qc =a ha in ha out)123 =a (114.15 90) a

    =5.02kg/sec.

    Coil design:

    :side (ref.)TubeFor

    ( )

    ( ) :For air side

    * + ( )

    ( )

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    R=0.75 kj/kg.k

    Ts1

    Ts1 =30.56

    0

    c

    Ts1 TDP wet surface

    Ts2

    Ts2 =25.450

    c

    Trm=

    =

    =20.90c

    Ai= =

    = 3 m2

    Ao=Ai*(18.5)= m2Nr=6

    ref= 0.898=

    Nc 26

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    NC=

    H =26*0.0254 = 0.66 m

    Aface=

    =1.731 m2

    Aface=H*LL = 2.62 m

    Tube length:

    L =

    Nt = 24 tubesFin calculations

    Assume

    (

    )

    ( )

    From chart

    Assume w=15cm

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    )

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    Techn isolv e Software for Evaporator coi l design

    Manufactur ing design proc edure:

    1st Step:

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    2nd Step:

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    3rd Step (Run Calculation from F9 button or button):

    Coil Manufacturing Report

    Recoil (5/8 inch - 38.1x50.8)

    1016 x 1264 4r 6f 40c

    DX 15938 / 20 / 04 / 6.00 / 1264 Cu/GI (40)

    Areas and VolumesAo = 86.919 m

    Ao' = 16.921 m/face m-rows

    Ai = 5.389 m

    Vi = 20.9 Litre

    Pipe ConnectionsSize = 67 mm

    Heat Transferho = 44.102 W/mC

    Ui = 3.780 kW/mCUo = 36.800 W/mC

    Ntu = 0.434

    Cr = 0.000

    Qt = e x Qmax

    = 0.352 x 350.216 = 123.242 kW

    Air Side DutyQt = ma (hao - hai)

    = 3.504 (87.49 - 122.66) = -123.242 kW

    Qs = ma x Cpa (dbo - dbi)

    = 3.504 x 1.066 (28.3 - 38.0) = -36.308 kWRate = 39.156 kW/cms

    Psychrometrics

    Bypass factor = 0.358

    Apparatus Dew Point = 22.8 C

    Refrigerant (R134a) DutySuperheat = 7.5 C

    Mass flow = 0.790 kg/s (approx)

    Mass flux = 101.7 kg/sqm.s (approx)

    Velocity = 0.080 m/s

    Qt = mr x dh= 0.790 x 156 = 123.26 kW

    Dimensions

    Height 1016.0 mm

    Length 1264.0 mm

    Depth 152.4 mm

    Rows 4

    Fins 6.00 fpi

    Weight 135.4 kg

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    CircuitingTubes High 20

    Tube Count 80

    Circuits 40

    Circuit Basis Tubes high

    Tubes/Circuits 2

    Unlinked tubes 0

    Serpentine 2

    Eq Length 3.8 mConnections Same end

    Tube (Staggered Pattern)ID 15.723 mm

    OD 16.586 mm

    Sx 38.100 mm

    Sy 50.800 mm

    FinThickness 0.200 mm

    Area factor 1.000 mm

    MaterialFin Cu

    Tube Cu

    Casing GI

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    Psychrometric Chart :

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    Condenser

    Condenser is an important component of any air conditioning system. In a typical

    refrigerant condenser, the refrigerant enters the condenser in a superheated state. It is

    first de-superheated and then condensed by rejecting heat to an external medium. The

    refrigerant may leave the condenser as a saturated or a sub-cooled liquid, depending

    upon the temperature of the external medium and design of the condenser.

    Classif icat ion of con densers (Based on th e external f luid) :Air cooled condensers(will be used in our case study so we will concentrate on it).

    Water cooled condensers(discussed before in chapter 2).

    Evaporative condensers(discussed before in chapter 2).

    Air cooled condensers:

    The circulation of air over the condenser surface is maintained by using a fan or a

    blower. These condensers normally use fins on air-side for good heat transfer. The fins

    can be either plate type or annular type. This type of condensers is commonly used in

    window air conditioners, water coolers and packaged air conditioning plants. The face

    velocity is usually around 2m/s to 3.5 m/s to limit the pressure drop due to frictional

    resistance. The coils of the tube in the flow direction are called rows. A condenser may

    have two to eight rows of the tubes carrying the refrigerant. The moist air flows over

    the fins while the refrigerant flows inside the tubes. The fins are usually of aluminum

    and tubes are made of copper.

    Holes of diameter slightly less than the tube diameter are punched in the plates and

    plates are slid over the tube bank. Then the copper tubes are pressurized which expands

    the tubes and makes a good thermal contact between the tube and fins.

    Air Cooled Condenser design :We will design the Air cooled condenser by Software and manually

    To design the Air cooled condenser by Software, we will use( Technisolve air cooled

    condenser software)

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    Input values to Technisolve air cooled condenser software:BarometerPressure (101.325 kpa)Type of Refrigerant (R134a)

    On Coil Temperature (dpt,wbt) (380

    C,340

    C)

    Condensing temperature (54.50C)

    Air Volume(9.582 m3/s)

    Air Velocity(3 m/s)

    Fin Height(1118 mm)Target duty(150 Kw)

    Number of Rows deep(6)

    Fin density(12 fpi)

    Finned Length(2858 mm)Tube size(5/8 inch-38.1 50.8)

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    Techniso lve Condenser coi l Manufactur ing design procedure:

    1st Step:

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    2nd Step:

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    3rd Step (Run Calculation from F9 button or button):

    Model

    Recoil (5/8 inch - 38.1x50.8)

    1118 x 2858 6r 12f 11c

    CD 15938 / 22 / 06 / 12.00 / 2858 Cu/GI (11)

    Areas and VolumesAo = 628.104 m

    Ao' = 32.762 m/face m-rows

    Ai = 19.285 m

    Vi = 75.3 Litre

    Pipe ConnectionsSize = 35 mm

    Heat Transferho = 71.064 W/mC

    Ui = 1.616 kW/mCUo = 29.092 W/mC

    Ntu = 1.607

    Cr = 0.000

    Qt = e x Qmax

    = 0.799 x 187.671 = 150.029 kW

    Air Side DutyQt = ma (hao - hai)

    = 10.672 (136.72 - 122.66) = 150.018 kW

    Qs = ma x Cpa (dbo - dbi)

    = 10.672 x 1.066 (51.2 - 38.0) = 150.029 kWRate = 15.651 kW/cms

    Psychrometrics

    Bypass factor = 0.020

    Apparatus Dew Point = 33.1 C

    Refrigerant (R134a) DutySub-cooling = 5.0 C

    Mass flow = 0.827 kg/s (approx)

    Mass flux = 1951.5 kg/sqm.s (approx)

    Velocity = 1.809 m/sQt = mr x dh

    = 0.827 x 181 = 150.029 kW

    Dimensions

    Height 1118.0 mm

    Length 2858.0 mm

    Depth 228.6 mm

    Rows 6

    Fins 12.00 fpi

    Weight 775.7 kg

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    CircuitingTubes High 22

    Tube Count 132

    Circuits 11

    Circuit Basis Tubes high

    Tubes/Circuits 12

    Unlinked tubes 0

    Serpentine 1/2

    Eq Length 41.8 mConnections Same end

    Tube (Staggered Pattern)ID 15.723 mm

    OD 16.586 mm

    Sx 38.100 mm

    Sy 50.800 mm

    FinThickness 0.200 mm

    Area factor 1.000 mm

    MaterialFin Cu

    Tube Cu

    Casing GI

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    Psychrometric Chart:

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    14.1. Design of Air cooled condenser manually:

    Given Data (1)

    (2) (3) (4) * (5) (6)

    Where { }

    *

    Assume

    =

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    Afrontal = L H = 3 1 = 3Assume 2.54

    Check on

    Tube side (ref.)

    ( ) ( )

    For air side

    By using induced draught far

    From tables

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    [ ( )

    ]

    (

    )

    Fin calculations

    Assume

    (

    )

    ( )

    From chart

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    Assume w=15cm

    )