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A discussion of heat vs cold

  1. Sep 13, 2010 #1
    EDIT: We are looking for someone to clear things up for us!

    An engineer friend of mine and I are having a debate about heat vs cold. Basically I am saying you can't 'add cold' to a system you can only add or take away heat and for some reason he is disagreeing. Chat of Gchat/AIM

    ****: 'adding heat' or 'adding cold' are two ways of looking at the same exact thing
    'temperature' is simply the vibration of atoms
    whether or not you increase or decrease it is irrelevant

    me: right but you cant really add cold
    you can only take away heat

    ****: sure you can
    its just another way of looking at it
    'taking away heat' is the same thing as 'adding cold'

    me: but what is atcually happneing
    on the molecular level

    me: you can keep adding heat to a system
    you cant keeep adding cold

    ****: uhu
    sure you can
    ull just never hit absolute 0

    me: so does heat have a theoritical limit

    ****: i dont know, heat turns to gama rays
    or some ****

    me: you can keep adding heat to a system

    ****: i dont know that

    me: yeah well you cant get to abosulte zero. thats the limit. tehre is no heat limit

    ****: i guess you'll approach a level where it takes an infinaite amount of energy to increase the heat of osmething same way as you cant approach that, you cant approach abs
    anyway i have a 200x003 to cool down, fortunately only to -54c

    me: you mean, let the air around it heat up

    me: adding cold is the retarded way of saying transfering heat away
    which is whats actaully happening

    ****: right and vice versa
    no bro

    ****: whats actually happening is whats actually happening
    the way we choose to describe it
    is a seperate story

    me: energy is passed from higher states to lower states

    ****: huh
    no
    if you're talking about electrons and valence leveels and **** that not heat
    yu're talkikgn about atomic vibrations, simple

    me: http://en.wikipedia.org/wiki/Cold

    ****: granted one causes the other

    me: Cooling refers to the process of becoming cold, or lowering in temperature. This could be accomplished by removing heat from a system not 'adding cool'

    ****: Cold (the opposite of hot) refers to the condition or subjective perception of having low temperature; it is the absence of heat or warmth.
    'subjective perception'
    exactly
    i couldnt have szidf it better myself

    me: no the subjective part is what you consider cold vs what i consider cold

    ****: but 'cold' has as much of a reality as 'heat'
    please
    cold is 'negative haet'
    'evil' is the absense of 'good' and 'good' is the absense of 'evil'
    one thing, different descriptions, dont be dumb
     
    Last edited: Sep 13, 2010
  2. jcsd
  3. Sep 13, 2010 #2
    your friend sounds like a smart guy and a good philospher. The only thing I dissagree with is when he talks about valence levels and gamma rays. Heat doesnt 'TURN' to gamma rays, heat gives off gamma rays.
     
    Last edited: Sep 13, 2010
  4. Sep 13, 2010 #3
    Note, this is the OP in the convo...
     
  5. Sep 13, 2010 #4

    russ_watters

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    I agree with your engineer friend. You could analyze a system flipping all the energy transfers around and still come up with the same answers.
     
  6. Sep 13, 2010 #5
    Hey thanks for finally being the one to help us out with this one.

    By the way, I went to your site and couldn't help but notice you looked familiar.

    Then I remembered Link deleted too much info
    Keep Gazin!
     
    Last edited by a moderator: Sep 13, 2010
  7. Sep 13, 2010 #6

    Andy Resnick

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    "adding cold" may be a useful mental conceit in some circumstances, but it's unphysical. It's like saying absorbing light is 'adding dark'.
     
  8. Sep 13, 2010 #7
    what is 'physical'? how is 'adding heat' any more physical? either way we're adding or subtracting energy. Heat or lack of heat is merely the effect.

    What about current flow in electrical circuits? by your reasoning that is completetly unphysical too as it relies on the 'absense' of electrons (electron holes) rather than the electrons themselves.
     
  9. Sep 13, 2010 #8

    russ_watters

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    Electricity is another good example of where the convention doesn't really matter. But let me give a real-world example that I see every day at work for the heating/cooling question from the OP. Consider the following statements:

    A heater does 1080 BTU of heating.
    An air conditioner does 1080 BTU of cooling.

    Both statements contain a positive value of heat transfer, but the heat is actually flowing in opposite directions. In the first example, heat into (a house, airstream, whatever) is positive, in the second, "cold in" is positive. Mathematically, the first might look like this:

    500 CFM of air rises from 70 to 90F. The thumb-rule conversion factor for CFM to BTU is 1.08 BTU/CFM*T
    So 500*(90-70)*1.08 = 1080 BTU

    For cooling, room temperature air is cooled from 75 to 55F. So 500*(75-55)*1.08 = 1080 BTU.

    Perhaps a physicist would cringe at the fact that both are positive, but it works fine for an engineer.
     
  10. Sep 14, 2010 #9

    Andy Resnick

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    Seriously?
     
  11. Sep 14, 2010 #10

    Andy Resnick

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    I realize I am picking a nit here, but 'heating' and 'cooling' are processes, 'heat' is a quantity of energy.
     
    Last edited by a moderator: Sep 16, 2010
  12. Sep 14, 2010 #11
    no, not seriously. you got me.

    Andy my point is simply that heat transfer, via conduction convection or radiation is just as physical or 'real' as a concept such as 'cold transfer' in the opposite direction. It's a matter of perception.
     
  13. Sep 14, 2010 #12

    Mapes

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    Seconding Andy here. In the context of physics (not necessarily everyday speech), "heat" and "cool" should really be restricted to verbs (cf. "Heat is not a noun," American Journal of Physics 69:2 (2001)). If we only speak of [thermal] energy, which can be added or removed from a system, then I think the confusion and debate largely disappears.
     
  14. Sep 14, 2010 #13
    well I second you, and you second Andy, which means I second Andy, but I DON'T second Andy so I don't think you second Andy.

    The only "reality" is thermal energy. The only difference between the verbs 'cool' and 'heat' is the direction of energy transfer. None is more real than the other.

    Seriously? The temperature of a body is the quantification of its energy. Hot or Cold are subjective perceptions.

    Perhaps 'heat' is convention due to the fact that it increases with temperature and is hence positive. But it is certainly no more 'physical' than cold.
     
    Last edited: Sep 14, 2010
  15. Sep 14, 2010 #14

    RonL

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    I'm glad to see this post from you, adding heat or cold is simply a play on words and any motion (no matter how small) produces an exact,equal change in both terms. So to me it becomes a simple matter of how it is said and either one should be correct.

    I have made mention of multiple positives on many occasions and yet it seems no one can see the net affect that I have tried to imply. So until I see something better than "it's impossible because no one has ever been able to do it" I will continue to work my brain (such that it is).

    I'm going to excuse myself from the forum for a while and maybe come back with a drawing or two at some point in the future.
    Can you check into why my account does not allow an upload option.

    Thanks Russ with all my respect.

    Ron
     
  16. Sep 14, 2010 #15
    ron, private message russ next time.
     
  17. Sep 14, 2010 #16
    Right I understand that on paper adding heat is like adding negative cold. But I am referring to what's actually happening on the physical level, in which case heat transfer can only happen from a warmer body to a colder one as energy is passed from one to the other. This is why I'm insisting you can't 'add cold' to a system, you can only add heat or let heat escape.
     
  18. Sep 14, 2010 #17
    adding cold is subtracting heat. if you "add cold" to a system you are "subtracting heat"
     
  19. Sep 14, 2010 #18
    In the physical world, heat transfer only happens in one direction. Always. From a hotter body to a colder body.

    As far as I understand, heat is also a measure of energy. So any object can have a certain level of heat there is no such measurement for cool.
     
  20. Sep 14, 2010 #19

    Matter of perception, dreimd. Thermal energy is exchanged yet the total energy of the system is conserved. (First law thermodynamics)
    Therefore in a closed system where one hot body conducts its thermal energy to a cooler one, the cooler one gains as much energy as the hot one loses. The system is seeking equilibrium. Hence, it can be just as realistically stated that its actually the cold that’s conducted in the opposite direction. The cool one has actually "cooled down" the hot one.


    The word "heat" is used synonymously with the word "energy". Heat, the way you mean it, isn’t a measure of temperature its simply an easy way to talk about temperature when we're dealing with systems. In the same way "cold" can just as easily be referred to as "negative heat".

    The only reason we use the word heat when talking about energy is because it has the same sign, as opposed to cold. It's more convenient.
     
    Last edited: Sep 14, 2010
  21. Sep 14, 2010 #20
    Yeah I have to agree with the posters.
    It is NOT possible to cool anything without removing heat.
    As such, removing heat is the dominant factor and "adding cold" has no meaning in and of itself without removing heat.
     
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