Results 1 to 5 of 5
  1. #1
    Join Date
    Mar 2016
    Location
    IRAN
    Posts
    163
    Rep Power
    3

    Centigrade VS Kelvin



    Dear Friends,

    Would you please tell me in most of Europe compressor catalogue, Why when they talk about evp. and cond. Temperature they say centigrade (C) but when they want to talk about Delta T , For example sub-cooling or super-heat they mention this by Kelvin (K). for example 5K superheat.

    Sincerely yours.



  2. #2
    Brian_UK's Avatar
    Brian_UK is online now Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
    Join Date
    Mar 2001
    Location
    Dorset
    Age
    70
    Posts
    10,650
    Rep Power
    52

    Re: Centigrade VS Kelvin

    When measuring the temperature of something we use the Celsius term because we are referring to a point in a temperature range that we know and understand.

    The range of 0 to 100 degrees came from Centigrade but we now use the term Celsius to describe the actual degree within that range. Obviously we also use the negative range as well.

    With a figure from the Celsius such as 20 degrees we would expect to feel comfortably warm. At 10 degrees C we would feel a bit cooler.

    If we now change to saying that the superheat reading is 10 degrees C does that mean that the superheat is feeling cooler?

    No, a superheat reading needs to tell us that there is a difference between two temperature points at an arbitrary temperature so we use the temperature term Kelvin.

    For example you could have 5K superheat at a suction temperature of 15C and you could also have 5K at -23C.

    So we use the different terms to describe to different meanings using the same Centigrade scale.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015
    Please support http://the100project.net/Home

  3. #3
    Join Date
    May 2012
    Location
    England
    Age
    54
    Posts
    1,328
    Rep Power
    30

    Re: Centigrade VS Kelvin

    .

    To avoid confusion, most measurements are done in metric centigrade but when we measure difference we do that in Kelvin. Delta T in Kelvin avoids confusion, for example if I said an evaporator had an air off at +5 with a 10K difference, you should know that the evaporating temp would be -5.

    Rob

    .
    .. ... -. .----. - / -- --- .-. ... . / -.-. --- -.. . / --. --- --- -..

  4. #4
    Join Date
    Mar 2016
    Location
    IRAN
    Posts
    163
    Rep Power
    3

    Re: Centigrade VS Kelvin

    Quote Originally Posted by Rob White View Post
    .

    To avoid confusion, most measurements are done in metric centigrade but when we measure difference we do that in Kelvin. Delta T in Kelvin avoids confusion, for example if I said an evaporator had an air off at +5 with a 10K difference, you should know that the evaporating temp would be -5.

    Rob

    .
    Thanks Rob and Brian_UK.

  5. #5
    Join Date
    Jan 2006
    Location
    Croatia
    Age
    63
    Posts
    2,136
    Rep Power
    24

    Re: Centigrade VS Kelvin

    Hi,

    Kelvin is related to thermodynamic energy ... you need to research that for yourself ... maybe to start here

    https://en.wikipedia.org/wiki/Equipartition_theorem


    Centigrade is related only to state of water freezing 0*C or evaporating 100*C ... it has nothing with energy ...
    good explanation by Brian_UK ... it is something we are familiar with ... like feeling hot or comfortable or cold ..



    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •