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  1. #1
    Join Date
    Mar 2008
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    10

    Sensible vs Latent heat

    Could someone help me explain what the differences is between these two concepts? I've been to a dozen websites that go into Einstein-speak... that's not what I need.
    Example:
    1) Natural gas furnace, blowing warm air: Is that Latent or Sensible?
    2) Heat pump blowing ambient air: Latent or Sensible?
    3) Fireplace burning an oak log: L or S?

    Huge help, thanks.
    DCN

  2. #2
    Join Date
    Nov 2003
    Location
    Rochester, New York
    Posts
    392
    senible is temp that can be measured. Example a thermometer. Latent heat is heat added but cause a change in state not temp. Like 212 water to 212 steam. the heat added to change water to steam is latent.

  3. #3
    Join Date
    May 2006
    Location
    Cumbria (England)
    Posts
    17

    latent and sensible

    sensible heat = If a subsatance is heated and the temperature rises as the heat is aded the increase is called sensible heat. Like wise if heat is removed from a substance. If the temperature falls the heat removel is also called sensible heat Heat which causes a change in temperature in a substance is called sensible heat

    latent heat= It has been established that all pure substances are able to change there state. solids become liquids and liquids become gases. It takes the addition of heat or the removal of heat to produce these changes. Heat which brings about a change in state with no change in temperature is called latent heat.

  4. #4
    Join Date
    May 2007
    Posts
    80
    All of your examples, OP, are sensible heat.

  5. #5
    Join Date
    Mar 2003
    Posts
    7,321
    sensible =change in temp......makes sense latent=hidden head, change in state, change in Rh. cannot be measured as easily

  6. #6
    Join Date
    Mar 2008
    Location
    Milwaukee, WI
    Posts
    5

    Smile Sensible Heat vs Latent Heat

    Hi DCN 289.

    To answer your question, all of the examples you listed are sensible heat.

    Sensible heat can be measured or felt when increased or decreased.

    Latent heat is heat gained or removed which causes a change in state of the substance, but not a change in measurable temperature- for example as ice melts into water or refrigerant converted into a gas or liguid. It is refered to as "hidden heat".

    In the field of AC for example, Latent heat would be the heat gained as refrigerant boils in an evaperator from a liguid into a gas, but without a change in measurable temperature. If heat was continued to be added until it completely boils all the refrigerant into a gas it would now superheat the refrigerant which then is measurable and thus becomes a sesible heat.

    I hope this was helpful.

  7. #7
    Join Date
    Feb 2007
    Posts
    5
    In air conditioning most heat loads contain both sensible and latent heat. As sensible heat is removed from the air, the supply air temp drops. As latent heat (humidity) is removed the temperature remains constant as the moisture in the air is removed and goes down the condensate drain. Humidity is often referred to as the latent heat load.
    Bob

  8. #8
    Join Date
    Mar 2008
    Posts
    10
    I want to thank everyone who took the time to reply... enormous help to me.
    I think I hit a stumbling block when I started to research it myself, so I turned to the HVAC-talk. It is evident that you all (as an industry) really think about what is physically happening to the air... My 10 year old asked me "dad, if we "turn up the heat" to make it warm in winter, why don't we "turn-down the cool" to make it cooler in summer?" She wanted to know why warm-air generation is called "heat" but cooling it is referred to only as "air conditioning" ... To me, both instances are "air conditioning".

    DCN

  9. #9
    Join Date
    Mar 2008
    Location
    Milwaukee, WI
    Posts
    5
    Quote Originally Posted by DCN289 View Post
    I want to thank everyone who took the time to reply... enormous help to me.
    I think I hit a stumbling block when I started to research it myself, so I turned to the HVAC-talk. It is evident that you all (as an industry) really think about what is physically happening to the air... My 10 year old asked me "dad, if we "turn up the heat" to make it warm in winter, why don't we "turn-down the cool" to make it cooler in summer?" She wanted to know why warm-air generation is called "heat" but cooling it is referred to only as "air conditioning" ... To me, both instances are "air conditioning".

    DCN
    One last comment. Trainiac brought up a good fact that sensible heat will co-exist with latent heat. My last sentence of my first response was not clear on that point. My example of refrigerant being boiled off will have sensible heat that can be measured, but that sensible heat should thoretically remain constant until all the refrigerant is boiled off and then any additional heat added will increase the sensible heat.

    To answer your daughters question- in theory, there is no such thing as cold, but either the absence of heat or presence of heat. We could say we increase the heat in winter and reduce the heat in summer to be technically correct for the scientist sake.

    Lastly, from a technical standpoint, air conditioning not only includes a comfortable temperature and humidity, but also conditions the air quality from pollution, particles, mold, spores, dust and stagnant air to name a few.

    Hope this helped too.

  10. #10
    Join Date
    Mar 2008
    Location
    Baltimore MD and Ridgebury PA
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    542
    Quote Originally Posted by trainiac View Post
    In air conditioning most heat loads contain both sensible and latent heat. As sensible heat is removed from the air, the supply air temp drops. As latent heat (humidity) is removed the temperature remains constant as the moisture in the air is removed and goes down the condensate drain. Humidity is often referred to as the latent heat load.
    Bob
    I've only just recently started in the HVAC business... I've been studying various texts and understand Sensible vs Latent... but it didn't really occur to me that dehumidification (as well as humidification) would be latent heat. Thanks for pointing this out!

  11. #11
    Join Date
    Nov 2004
    Location
    SW FL
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    6,273

    Exclamation HVAC 101 Test

    Quote Originally Posted by DCN289 View Post

    Could someone help me explain what the differences is between these two concepts? I've been to a dozen websites that go into Einstein-speak... that's not what I need.
    Example:
    1) Natural gas furnace, blowing warm air: Is that Latent or Sensible?
    2) Heat pump blowing ambient air: Latent or Sensible?
    3) Fireplace burning an oak log: L or S?

    Huge help, thanks. DCN
    Test is in one hour

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    Designer Dan
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    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    . My 10 year old asked me "dad, if we "turn up the heat" to make it warm in winter, why don't we "turn-down the cool" to make it cooler in summer?" She wanted to know why warm-air generation is called "heat" but cooling it is referred to only as "air conditioning" ... To me, both instances are "air conditioning".

    We don't turn down the cooling when we want it cooler, just because people got use to up being more.

    You are correct. Air Conditioning is: heating, cooling, humidifing, dehumidifing, or cleaning/filtering AIR.
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  13. #13
    Join Date
    May 2007
    Location
    Jakarta Indonesia
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    2
    Quote Originally Posted by platchford View Post
    I've only just recently started in the HVAC business... I've been studying various texts and understand Sensible vs Latent... but it didn't really occur to me that dehumidification (as well as humidification) would be latent heat. Thanks for pointing this out!
    it's mean you didnt understand what is latent and sensible heat..
    learn it again..

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