Convection Definition and 178 Threads

HI when dealing with natural convection, we use grashof's number. suppose we have a heated plate of temperature Tp. and heat being transferred to surrounding air by convection, air of temp Ta. So film temp is Tf = 0.5(Tp + Ta) If grashofs numbers, Gr = \frac { \beta gL^3 \delta...

What expression should be used to calculate Nusselt number for free convection (of air) in a vertical channel with walls at different temperatures? I have the Bar-Cohen and Rohsenow equations, but I am unsure which situation this corresponds to (and thus which constants to use). Symmetric...

Homework Statement An audience of 1800 fills a concert hall of volume 2.2×104 m^3. If there were no ventilation, by how much would the temperature of the air rise over a period of 2.0 h due to the metabolism of the people (70W/person)? Assume the room is initially at 293K. Homework...

convection...nuclear reactors...** hey guys, there is one question i am having a great deal of trouble trying to find formulas and stuff for out of my textbook and don't really have the time or patience to search through hundreds of google pages :bugeye:. so any help on this would be greatly...

Hello everyone, new guy here. I'd like some other minds on an on-going debate i have with quite a few people. The subject is "Radiant Floor Heat". I'm not going to cover any formulas at this point as i need to convey the conceptual side of things first. We know that heat is transferred...

1. Assume a cubical pot of water 1 m on each side. Heat is applied to the bottom of the pot. Assume the water at the bottom is held at 99 degrees C while the water at the top of the pot is 4 degrees C. Estimate the convective heat flow (using algebraic physics). Step 1: Compute the net...

This is a forced convection heat transfer problem and would appreciate any help! Stack of steel billets is placed in a cooling chamber. All billets of the same row are touching each other and each row is spaced of 5 in. I want to calculate the convection coefficient and pressure drop across...

Homework Statement What is the heat transfer from a 60W electric light bulb at 127C to the stagnant air in a room at 27C. Approximate the bulb to a 50mm diameter sphere. What percentage of the power is lost by free convection?Homework Equations Nu=2 + 0.6(Gr^1/4)(Pr^1/3)...

Hi, I was wondering if someone could help explain how the following shapes would affect convection. What it is is a heat plate with nothing, a bundle of tubes, and just fins. It's in a vertical tube and the air flows upwards. I understand convection but I don't get how it would be affected in...

As I remember learning in school, heat cannot flow from cold to hot. But isn't that true only for conduction and convection? Radiation heat is purely Infrared waves, and there should not be any issue with that. Please correct if I am wrong.

POWER FROM A CONVECTION LOOP: this is a scaled down version of the solar tower updraft system planned for austrailia, or the SHPEGS project with water/silica jell adsorption instead of ammonia absorption, or the water spray downdraft 'culvert on a hillside', proposed for hot dry...

I am trying to find out how fast a vertical cylindrical water column heats due to the ambient temperature. I already calculated the heat transfer due to conduction but I am now interested in the role of natural convection. So to be clear there is a temperature difference between the walls and...

I am learning the concepts of thermodynamics and this one is confusing me! The question is - If I pour myself a cup of hot coffee and then the phone rings, is it better to pour the cream (room temperature) before walking away, or when I return in order to have the hottest coffee when I return...

There's a debate these days related to the australian ban of traditional light bulbs, because of the loss of heat energy: http://www.ens-newswire.com/ens/feb2007/2007-02-21-01.asp" But in a colder place than Australia (like Norway), it think this number would be lower than 66% because some of...

What exactly is convection?

Hi all I've been calculating heat convection off a horizontal heated plate to still cool air around it. Since the plate has a size of 50m2 the GrPr number is turbulent i there's no equation in my book to calculate heat transfer by convection for GrPr > 10^11, so i used the equation of GrPr at...

Hey. I've been pondering on and off for a while now how exactly energy is transferred between two gas atoms, with different energies, via collision. Specifically how the electrons, photons, neutrons, protons, and any other particles that are used for energy transfer in convection, interact...

Does warm water rise or fall in cold weather? I think it falls Does it have to do with convection??

Is there a formula for turbulence pressure that is a function of temperature ( in the convection zone of a star )?

Hi all! I am currently reading the text "Practical Bifurcation and Stability Analysis" by Seyedel for an introduction to practical bifurcation theory. I do not tatolly understand the theory and hope that some of you could help explain to an idiot like me. I have read till P.80 of the books...

convection question?? MechE or Civil? I'm just asking out of curiosity, and I'm just a first year engg student...so it maybe non-senses... In an enclosed system, with heat being generated. Let's say a very fancy toast factory, where bread becomes toast. The factory itself have already...

Hi, Just a quick question, I just want to check that i am on the right lines! When heat escapes through the top of a container which does not have a lid, is that due to convection? i/e hot air is less dense than cold air, so rises. Cheers o:) Gemma o:)

With heat transfer I'm having trouble seeing the difference between convection and radiation. My book says convection is the heat transfer between a solid and a liquid or gas, like an oven in a room. Sunlight is supposed to be radiation, but if one looks at the sun as being the oven, and the air...

I am thinking that convection current does happens not because of changed in density. I based this argument with viewing the problem from particle / molecular scale. Density = Mass/ Volume. Yet in molecules of water, discussing mass and volume would less likely to be relevant as mass and volume...

I have to do a demonstration to show convection in class. I was wondering what could be a simple experiment to set up in which I could show that convection exists. I've had a few ideas and am wondering if you could come up with any. :shy: Thanks, lcg

I know that there is an equation for conduction, and radiation, but is there an equation for convection?

Do convection currents occur in all bodys of water and gas? Or are they only at a certain temperature, under certain circumstances?

Hey - do you think anyone could help explaining the process of conduction and radiation, convection currents for me? Physics exam next Monday, and I have to start studying soon! Also, what is density measured in? Kg/M^2? Thanks in advance!