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  1. #1
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    liquid storage and suction accumulator



    HI sirs
    I've designed a heat pump system and use a suction accumulator to accommodate the winter operation. If it's necessary to add a liquid storage for the capacity variables? pls advise.

    regards
    LC


    I hear...I forget;I see...I remember;I do...I understand

  2. #2
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    Re: liquid storage and suction accumulator

    If your heat pump is one with small amount of refrigerant charge, perhaps you could use a suction line accumulator to handle the variation in charge requirement in switching between heating/cooling modes. But this is so only if you use a 4-way reversing valve to switch condenser and evaporator to suit demand (cooling or heating). Other switching methods may not have this issue.

    However, if the internal volumes of the condenser and evaporator differ very much, you are going to need extra storage capacity during at least one mode of operation, may be during heating/ or cooling depending on the system design, passive volume within the system and the amount of charge


    raja

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    Re: liquid storage and suction accumulator

    Quote Originally Posted by Lc_shi View Post
    HI sirs
    I've designed a heat pump system and use a suction accumulator to accommodate the winter operation. If it's necessary to add a liquid storage for the capacity variables? pls advise.

    regards
    LC

    What type of metering device does it have? I would use a liquid reciever if it has a thermostatic expansion device to allow for the verible demand.

    Cheers taz.

  4. #4
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    Re: liquid storage and suction accumulator

    Hi Sir
    How do u think if the suction line accumulator to take the task ? heating mode's refrigerant mass flow is about 50% of cooling mode,if the accumulator can store the extra refrigerant ,is it all right?

    thanks
    LC
    I hear...I forget;I see...I remember;I do...I understand

  5. #5
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    Re: liquid storage and suction accumulator

    Quote Originally Posted by Lc_shi View Post
    Hi Sir
    How do u think if the suction line accumulator to take the task ? heating mode's refrigerant mass flow is about 50% of cooling mode,if the accumulator can store the extra refrigerant ,is it all right?

    thanks
    LC

    In principle it could work but I personaly do not like the idea of using the suction as a storage area. I prefer to have all my excess refrigerant in liquid form and in the receiver.

    Cheers taz.

  6. #6
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    Re: liquid storage and suction accumulator

    Quote Originally Posted by Lc_shi View Post
    Hi Sir
    How do u think if the suction line accumulator to take the task ? heating mode's refrigerant mass flow is about 50% of cooling mode,if the accumulator can store the extra refrigerant ,is it all right?

    thanks
    LC
    What you must bear in mind is the compressor is no more than a glorified suction pump. It will suck as much gas as it can possible get within the constrainst you set it, ie speed, bore, stroke, and effiency. So you cannot store refrigerant in the suction with out affecting the operating parameters of the system.

    cheers taz.

  7. #7
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    Re: liquid storage and suction accumulator

    But this is so only if you use a 4-way reversing valve to switch condenser and evaporator to suit demand (cooling or heating). Other switching methods may not have this issue.
    What methods besides reversing valves are used in bidirectional heat pumps? Every heat pump I know of uses a reversing valve.
    "If Hannah was an air handler, I would be a condensing unit so I could open her TXV and pump my refrigerant through her coils." - a HVAC friend of mine

  8. #8
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    Re: liquid storage and suction accumulator

    Quote Originally Posted by star882 View Post
    What methods besides reversing valves are used in bidirectional heat pumps? Every heat pump I know of uses a reversing valve.

    Heat pupms do not have to be bidirectional always. Switching the heat transfer fuid (feeding the application) between the evaporator and condenser to obtain heating/cooling goes well with single direction systems. I do not have examples to post, but this method has been researched, and found better suited for refrigerant mixtures

  9. #9
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    Re: liquid storage and suction accumulator

    Quote Originally Posted by lraja View Post
    Heat pupms do not have to be bidirectional always. Switching the heat transfer fuid (feeding the application) between the evaporator and condenser to obtain heating/cooling goes well with single direction systems. I do not have examples to post, but this method has been researched, and found better suited for refrigerant mixtures
    But what is the device that actualy switches direction?
    somthing has to change the flow from one way to the other.

    Cheers taz.

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    Re: liquid storage and suction accumulator

    The excess refrigerant can also be stored at low load conditions in the condenser, a technique used in many chillers (Climaveneta, Carrier, Rhoss, Clivet, Ciat,..)
    At low load, you then have at the same time an oversized condenser, so capable of storing refrigerant and even subcool it.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  11. #11
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    Re: liquid storage and suction accumulator

    Quote Originally Posted by Peter_1 View Post
    At low load, you then have at the same time an oversized condenser, so capable of storing refrigerant and even subcool it.

    I agree the oversized cond when in low load conditions stores liquid but more benificial to the system when in high load conditions the oversized cond will be capable of working better.

    Cheers taz.

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