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  1. #1
    Join Date
    Aug 2015
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    China
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    R134a Temp/Press do not correspond to PT Charts!

    Hi Everyone,

    I am a new member here. I am a mechanical engineer doing an internship in China with a refrigeration products manufacturer. We have a very small device in design for testing.

    I do not know how to charge system critically. In fact, I do not know how much to charge it at all. I have this Chinese technician with me who does it by experience. He has inserted a 2 meter cap tube, also by experience.

    I run the prototype without cooling load and observed the temperatures and pressures at Compressor Inlet, Condenser Inlet, Static Orifice Valve Inlet and Evaporator Inlet (just after cap tube). I also have a thermocouple attached to Evaporator Coil outlet. The system is so small that I do not consider any pressure losses. We are using R134a.

    Now, the results I got were confusing. At condenser inlet, I had 110 PSI and 38 deg C. At Orifice Inlet, I had 110 PSI and 32.9 deg C. The latter do not correspond to psychometric charts. I have other values like that too. We are supposed to have sub-cooled liquid here and I can see liquid through the transparent gauge pipe.

    Can anyone explain this?

    Thanks

  2. #2
    Join Date
    Aug 2010
    Posts
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    Quote Originally Posted by ZhuoHan View Post
    At condenser inlet, I had 110 PSI and 38 deg C. At Orifice Inlet, I had 110 PSI and 32.9 deg C. The latter do not correspond to psychometric charts. I have other values like that too. We are supposed to have sub-cooled liquid here and I can see liquid through the transparent gauge pipe.

    Can anyone explain this?

    Thanks
    And you do have subcooledness.

  3. Likes ZhuoHan liked this post.
  4. #3
    Join Date
    Aug 2015
    Location
    China
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    After your comment, I looked up the R134a charts online and came to know that we have been using the hard copies of some other refrigerant's charts... This is so embarrassing.

    Thanks a lot.

  5. #4
    Join Date
    Aug 2010
    Posts
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    Quote Originally Posted by ZhuoHan View Post


    After your comment, I looked up the R134a charts online and came to know that we have been using the hard copies of some other refrigerant's charts... This is so embarrassing.

    Thanks a lot.
    The numbers aren't that important, but your post suggests you don't have a good grasp of the idea.

  6. #5
    Join Date
    Aug 2015
    Location
    China
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    I agree with you. I am still new to this. Was working in construction before. I have a long way to go.

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