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  1. #1
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    refrigerant critical temperature

    hi friends.

    i am studying the HVAC system and trying to completely visualize the working condition for refrigerant throw out all process

    in the condenser coil the gas will condense at the designed condensing temperature. (which normally can be between 15C higher than the ambient temperature)

    my question:
    how much recommended the refrigerant critical temperature to be higher than the condensing temperature.

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  2. #2
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    You don't want to exceed the critical temperature, but you also want the condensing temperature low enough to keep your compression ratio down but enough pressure drop across the metering device to properly feed refrigerant.

    This all relies on a lot of different parameters and most systems are different. If you are looking for a rule of thumb, I am not aware of one for this situation.

    Sent from my SM-G965W using Tapatalk

  3. #3
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    Quote Originally Posted by mohad_i View Post
    my question:
    how much recommended the refrigerant critical temperature to be higher than the condensing temperature.

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    I think your question really is:

    how far below the refrigerant critical temperature should the condensing temperature be?

    The basic answer is: as far as possible.

    However, this is more a refrigeration system deign question than a pressures question. If you convert the critical R410a you will see that it is not all that low. My PT chart goes to 613 psi and says that pressure is equal to about 150 degrees. So the only way to.exceed that is to that operate your system with a highrr than 150 degree condenser, which is not likely. Instead you are going to stick to standard design and that by itself keeps your design within range.

    How does that sound?
    Hmmmm....smells like numbatwo to me.

  4. #4
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    You are looking at the equation from the wrong direction.

    The correct answer is: as much as you can afford. <g>

    The Critical Point is a limiting factor; yes - but it's not much of a useful reference point in relation to 'proper' head pressure.

    The lowest head pressure which will provide adequate refrigerant flow at the metering device will always provide the lowest compression ratio across the compressor and so the greatest operating efficiency at the lowest operating cost.

    But when the system is being designed Cost will almost always be an important consideration. Larger condensers are better - but they cost more. So while, yes; you are trying to get the operating head pressure as low as possible - you still have to sell the product. Design will always be a compromise between Performance, Cost, and Quality.

    You say: "i am studying the HVAC system and trying to completely visualize the working condition for refrigerant throughout all of the process."

    This is an excellent approach for you to take and one which is sometimes neglected by students. So please describe what you already know about the Refrigeration Process and let's explore it one area at a time. Everyone here can pitch in and we'll go through it all with you.

    PHM
    ---------------


    Quote Originally Posted by mohad_i View Post
    hi friends.

    i am studying the HVAC system and trying to completely visualize the working condition for refrigerant throw out all process

    in the condenser coil the gas will condense at the designed condensing temperature. (which normally can be between 15C higher than the ambient temperature)

    my question:
    how much recommended the refrigerant critical temperature to be higher than the condensing temperature.

    Name:  image.png
Views: 187
Size:  326.6 KB
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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