# Why is hot dry air impossible/impractical?

• posted on September 29, 2008, 3:17 am

On Aug 9, 8:02 pm, .p.jm@see_my_sig_for_address.com wrote in http://groups.google.com/group/alt.hvac/msg/9646d0d0d4cfa110?hl=en :

The overwhelming majority of heat emitted from a fire, is convective heat, not radiant heat. There is some radiant heat but it is very small compared to the convective heat.

Um, the human body can give of heat via radiation as well as conduction and convection. If you put your hand near a piece of extremely cold metal, you'll feel a perceptible amount of cold even if you don't touch the metal. This is an example of radiant cooling. There is a sharp difference in temperature between your hand and the cold metal. Physics wants to equalize the temperature and will attempt in whatever way possible to do so. If you are not touching the metal [a painful conductive cooling], then the next option to equalize the temperature is for your hand to emit IR radiation and warm the metal. In this case, your hand is the thermal radiator. Your hand emits radiant heat toward the cold metal.
To your hand, this is radiant cooling. For the cold metal, it is an example of radiant heating, because the IR radiation from your hand will warm up the metal.

Why not? What's wrong with dry convective heating?

What makes hot dry air impossible?
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• posted on September 30, 2008, 12:43 am
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WRONG!!!!!!

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• posted on September 30, 2008, 12:54 am

Convection is what causes the fire to point upwards. Hot air travels up via convection. Put your hand below or on the side of a flaming candle, you won't feel much heat [esp. below the below the flame]. However, if you place your hand above the candle, you get a painful amount of heat. This is because most of the flame emits heat via convection. Only a trace amount of the fire's heat is emitted through radiation.
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• posted on September 30, 2008, 2:02 am
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Well I am not to argue with you, however any benefits that you are getting from fire is radiant heat what ever goes up it is waste and yes it is definitely hot strait above of it however I would not call it convection heat. Convection heat is consider your base board water or electric as long you don't have forced air over but natural convection. Tony
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• posted on September 30, 2008, 4:10 am

Fire consists of hot gases that move upwards. If it were radiant heat, then the heat would not specifically move away from the source of gravity. If you aim a butane torch downward, most of the heat will still go up. If it were radiant heat, then it heat from the torch would move downward.

What mechanism other than convection would cause the heat to go upward as opposed to in all directions?

Huh? "base board water or electric"??
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