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Questions tagged [convection]

transport mechanism involving bulk motion of a medium

Convection is that mode of transport or mass or energy which results from bulk motion of the transporting medium. The term is commonly used to describe transport of heat energy and/or momentum. Convection is principally of two types- natural and forced. Natural convection results from gradient in the density of a medium, while forced convection results from an external forcing agent e.g a pressure gradient.

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Why are radiators always placed under windows?

I don't know if anyone else has noticed this but in most buildings and most rooms, radiators are predominantly placed under a window. Now, in my eyes, that is the worst place to put them; hot air rises, reaches the window (which no matter how well…
turnip
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What exactly is the difference between advection and convection?

After reading Wikipedia articles on advection and convection, I still cannot determine whether there is a consensus on a difference between these two terms. Sometimes, the term convection seems to include advection and diffusion, sometimes not.…
Wok
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If air is a bad conductor, how does fire heat up a room?

If air is a bad heat conductor, how does fire heat up a room? Could someone help me, as I really don't get this?
Kaira Chunawala
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What is the exact difference between diffusion, convection and advection?

I have tried to explore the information but still not very clear on the exact difference between diffusion, convection and advection. Can anyone help me out to clear my concept?
Hamayun
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What exactly is the difference between radiation, conduction, and convection?

Okay, so everywhere I've read, I hear the main difference is the requirement of a medium. But for example, if you take the case of heat 'radiating' from a red-hot iron, isn't that actually convection and not radiation? I mean, isn't the temperature…
sciencerocks
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Why does a match go out if you hold it so the flame is up?

I have noticed something which may have been noticed already: take a match, and light it, then hold it so that the flame is directly above your hand. The flame will eventually go out. My guess as to why this happens is that the convection causing…
Tdonut
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What does it mean that a substance can be smelled from far away?

I thought about this question in the middle of this video. Ok, Thioacetone takes the price for the World's smelliest chemical, I can accept it (why not?), but what about You can smell one drop of this substance, almost instantly, from half a…
Enlico
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Convective and Diffusive terms in Navier Stokes Equations

My question has 2 parts: I just followed the derivation of Navier Stokes (for Control Volume CFD analysis) and was able to understand most parts. However, the book I use (by Versteeg) does not derive it in its entirety. He pulls a lot of results…
user7950
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A theoretical model for evaporation occurring when wind is blowing over the surface of water

I've recently done an experiment in which I was studying the variation of the cooling rate of hot water in a draft (wind). The air was blown directly over the surface of the water (kept in a cylindrical container). After plotting the graph, I saw…
Student
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Does opening both windows in a room cool the room twice as fast?

It's getting colder where I live (~40 degrees Fahrenheit). The place where I live (college dormitories) pumps the heat up into the 80's, so I keep the windows open most of the time. I noticed that, when I open both windows, the room seems to cool…
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What is the microscopic picture for warm air rising?

The usual explanation for warm fluids rising past cooler ones is that the warmer fluid has a lower density. I'm trying to understand what this looks like at a molecular scale. The density seems to be a large-scale phenomenon, and I don't…
Mark Dominus
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How does the sun's surface conduct thermal energy from the convective zone to the corona?

How does the surface of the photosphere conduct thermal energy from the convective zone to the corona, while remaining at such a relatively low temperature itself? It seems odd to me that the photosphere is wedged between the convective zone and the…
Giffyguy
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Is this a weather phenomenon or an instrumental artifact?

The radar image of the midwest provided by Weatherunderground at 10:30 PM Central time, May 8 2011 has odd patterns. Are these patterns real? Perhaps caused by large scale convection over cities? Or are they artifacts of radar placement? Here is…
David LeBauer
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Physics of the convection oven

I don't understand how convection ovens can cook food faster than radiant heat ovens. Guides to convection ovens claim that they cook food 25-30% faster than radiant heat ovens, but do not really explain the physics of it. For example, let's say we…
Ambrose Swasey
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How does hot air rise?

If a balloon is filled with hot air, it is rising due to buoyancy: the mass of the hot air inside the balloon is lower than the mass of the same volume of the cold air outside the balloon cavity. However, in absence of a balloon, how and where the…
Roger V.
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