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  1. #1
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    Question A question about the pressure drop in coil .

    Usually in heat exchanger designing,the less the pressure drop, the better.

    But a professor said, in an air cooled condenser designing, we must keep an appropriate Presure drop. (otherwise the two phase refrigerant will go to the expansion valve.)
    and the pressure drop of the refrigerant (here R22) in the tube of a condenser coil shouldn't less than 4 psia.(The unit is about 100 tons capacity,and the pressure drop in our first selection is about 1.8psia)

    It's really a new idea for me. I wondered if there are some experience pressure drop date for it?

    I can't find informations about it. so I come here find help.

    Thanks for all reply.
    Last edited by jackcn; 23-04-2004 at 08:07 AM.

  2. #2
    shogun7's Avatar
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    Smile Re: A question about the pressure drop in coil .

    The pressure drop for an air cooled condenser is about the same as it is for an evaporator and that’s a maxium of 3 psi. Air cooled condensers normally have one or more fans and motors to move air usually at a rate of 500 to 1000 cfm per compressor hp. Air cooled condenser capacity are based on the total external area, temperature, time , and air velocity. Using these values, the capacity of an air cooled condenser varies between 1 and 4 btu/cuft/hr/ *f

  3. #3
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    Re: A question about the pressure drop in coil .

    Hi
    I would tend to think in the terms of saturated temperature loss say 1k for a condenser. 3 psig is a good round number, but relates to a different temperature drop for each refrigerant, better to talk about a drop in saturation (R12 would have a much greater temperature drop for 3 psig than say R744)
    Kind Regards. Andy

  4. #4
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    Re: A question about the pressure drop in coil .

    Maintaining a sufficient two-phase refrigerant velocity would be the primary concern for someone designing an evaporator or condenser coil. This is to allow proper wetting of the inside surfaces of the tubes which provides the desired heat transfer.

    Pressure drop, however, is a function of refrigerant velocity. So one can think of a "desired" pressure drop for a coil if it is being related to velocity. But this Prof finds this to be an awkward way of thinking. In his humble opinion, one should be more concerned about a maximum desired pressure drop for the coil.

    Specifically, pressure drop is roughy proportional to the length of the circuit and the square of the velocity.
    Prof Sporlan

  5. #5
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    Re: A question about the pressure drop in coil .

    [QUOTE=Prof Sporlan]

    Pressure drop, however, is a function of refrigerant velocity. So one can think of a "desired" pressure drop for a coil if it is being related to velocity. But this Prof finds this to be an awkward way of thinking. In his humble opinion, one should be more concerned about a maximum desired pressure drop for the coil.

    QUOTE]

    So you are saying pressure drop is unimportant
    I have never had the need to design a coil (yet) so please elaborate

    I have been taught to work to an agreed temperature drop, but in doing this keep a velocity in mind. In hot gas lines this would be 15m/s I am assuming a little less would be appropiate in a condenser coil.

    Please comment as I am learning here

    Kind Regards. Andy

  6. #6
    shogun7's Avatar
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    Re: A question about the pressure drop in coil .

    We in the colonies like to think in terms of pressure drops when we consider heat transfer in closed system heat xchangers. I have never considered t in terms of temperature, although thats probably just as good if one thinks in terms of a particuar application.

  7. #7
    ISMED BURMAWI's Avatar
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    Re: A question about the pressure drop in coil .

    Thank your info, i can check this data

  8. #8
    ISMED BURMAWI's Avatar
    ISMED BURMAWI Guest

    Re: A question about the pressure drop in coil .

    According to me, decrease the pressure on the condensing unit of media-related trade refrigerator as kalor (the air). While air temperature is always based on the change of time (day or night). To maintain different temperature between air and the incoming coil after coil out from the result of the movement of heat from the refrigerant to the air to the process of condensation in the perfect kondensor.

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