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Thread: TXV flow rate

  1. #1
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    TXV flow rate

    Hello all, I am new to this site and was wondering if anyone could help me with a problem I am trying to answer. I am currently attending a technical school for HVACR and am filling out a academic excellence test. The question I cannot solve nor find in my text book is, as follows: "What is the flow rate of a TXV in a r410a system as compared to the flow rate of a TXV in a r22 system". The answer choices are: A-equal, B-40 to 70% higher, C-15% greater, D-15% less.
    Has anyone here perchance, ever came across this info? If so could you let me in on the solution. Thanks for your time everyone.

    Maximo

  2. #2
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    I would think equal. 410 is higher pressure. Both work on the same principle, superheat since they use a TXV. I also am in school so i may be wrong.
    Last edited by oldplanemech; 11-16-2010 at 10:09 PM. Reason: addition

  3. #3
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  4. #4
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    Thanks for your replies. I am leaning towards the answer of "equal" also since I don't remember being told that r410 absorbs heat more efficiently than 22, only that it is more "environmentally friendly". It does operate at higher pressure but the TXV and all other system components are designed for that. If the heat absorption capabilities are equal and the two systems are equal in tonnage then the flow rate should regulate superheat identically. My only question now is if I am correct in assuming the heat absorption characteristics to be the same between the two. Any insight would be greatly appreciated.

  5. #5
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    Quote Originally Posted by Maximo3 View Post
    Thanks for your replies. I am leaning towards the answer of "equal" also since I don't remember being told that r410 absorbs heat more efficiently than 22, only that it is more "environmentally friendly". It does operate at higher pressure but the TXV and all other system components are designed for that. If the heat absorption capabilities are equal and the two systems are equal in tonnage then the flow rate should regulate superheat identically. My only question now is if I am correct in assuming the heat absorption characteristics to be the same between the two. Any insight would be greatly appreciated.
    Maybe a bit of research on your part would benefit you.

    I'm sure the answer is close at hand, you just have to find it.

  6. #6
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    410a is supposed to have higher volumetric heat. so it should take less of it to do the same job. so flow should be less. I think.

  7. #7
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    Don't you hate it when you ask a question, then get a question not a answer?
    I've also heard that no question is a dumb question, but thats not the case for some of the answers.

  8. #8
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    Quote Originally Posted by WFL-TX View Post
    Don't you hate it when you ask a question, then get a question not a answer?
    I've also heard that no question is a dumb question, but thats not the case for some of the answers.
    In my experience, simply giving a student or an apprentice the answers turns them into idiots that can't think for themselves.

    I very often answer questions like this with directed questions to help them think in the right direction.

    Nothing personal.

  9. #9
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    Quote Originally Posted by fearlessfurnace View Post
    410a is supposed to have higher volumetric heat. so it should take less of it to do the same job. so flow should be less. I think.
    Yep. Lower volumetric flow.
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  10. #10
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    Max.

    The answer IS in your text books. You have to read them more then once. I know. They can be a bit boring sometimes(I'm still trying to finish my first one ).

    Often. It can help to write down in your own words what you read.
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  11. #11
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    Max,

    as you know? there are 12,000 btu's per hour or 288,000 btu's in 24 hours

    if you need 12k btu's? in your evaporator?

    you need to find how many btus per pound in r-22 and

    how many btu's per pound in r-410a

    this can be found on an enthalpy chart

    if you know the enthalpy and density of the refrigerant?

    you will then know which one needs more FLOW!

    the refrigerant with the MOST btu's per pound would require LESS refrigerant .

    by the way, here is a nice refrigerant piping web site.
    http://www.mcquayservice.com/mcquayb...011_120407.pdf

    you might like it?
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  12. #12
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    Thanks again all

    You guys were very helpful. I went ahead and asked my instructor about this question, and he also directed my attention to the enthalpy characteristics of the two refrigerants. Turns out the flow rate for r410a is less since it does absorb quite a bit more btu per volume. I realized it takes less of the r410 to absorb as much heat as the r22. I have to admit, i wouldn't have gone to the enthalpy chart so soon had I not asked for help, but hey , Im here to learn. You have all been quite helpful, thanks again.

  13. #13
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    good job Max!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    I WILL SELL WORK,GENERATE BUSINESS, GO GET NEW CUSTOMERS!
    YOU SHUT THE HELL UP AND QUIT RUNNING YOUR MOUTH!

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