Convection Definition and 194 Threads

So this is my current problem: I have block of solid material that separates two bodies of gas. The temperature of all three is known (and presumably all different). The solid material is also being heated, equally throughout its volume. I want to know the instantaneous heat transfer...

I am working on a problem involving heat transfer from a horizontal pipe in air. I am having trouble with it and not getting the solution I expect, and I think it is because of the convection component of the heat transfer. The general formula I am following for convection from a horizontal pipe...

Homework Statement A flow of air at 27C and 1 atm is hydrodynamically fully developed in a 1c I.D pipe with uav=2m/s. Plot(to scale) Tw,Tb, qw as a function of the distance x after Tw is changed or qw is imposed. a) in the case for which Tw=68.4 C = constant b) in the case for which qw=378...

Hello, I am working on a case in which I'm trying to calculate the heat load of a house (actually mine). I want to be sure that the calculations were done correctly during the design phase. Disregarding the methods at various web sites (most of which are commercial), i'm doing it in a...

Ok please can someone help or at least point me in the right direction with this question please? I have air flowing through a pipe which is heated to 477 degrees via burners on the outside. The pipe itself is heated to 550 degrees and there is a thermocouple inside the air flow. However, the...

Hello! thanks in advance for any help you can throw my way! I am in my masters year of an Acoustical Engineering course in the UK. We have been set a group design project to with essentially setting up a forced convection cycle in a room in order to redistribute the heat from a radiator and...

Homework Statement A tent being considered for cold-weather conditions has insulation on the top and sides with a conductivity, k = 0.040 W/(m*K) and a thickness, l = 0.50 cm. The tent (and surrounding medium) has the following conditions: a heater (inside the tent) producing heat at a rate...

The other day I was at a football match and I had a cup of tea in a styrofoam cup. The tea was practically boiling - far too hot to drink, but the cup was only warm to the touch. I know that if the tea had been in a china cup or mug it would hve been uncomfortably hot to pick up. Why does the...

Both are near silent and 100% (in)efficient, but does the convection heater (with the electric coil where heat rises naturally) make the room more stuffy as I've sometimes heard, or perhaps even deplete oxygen?

I am trying to calculate the length of a pipe needed for an air cooling system I have found the following formulas: R=1/(h*a) where h is the convection coefficient and a is the surface area. h=Nu*(k/L) where Nu is the nusult number and k is the thermal conductivity. a=π*d*L where d is the...

I have a transformer in a box that is cooled using natural convection. There are louvered openings on the box to pull cool air in the bottom and let heated air out of the top. How do I determine how much heat is actually leaving the enclosure? Info that I have is the area of the enclosure, the...

Hello, I'm thinking about a natural convection problem where you have turbulent flow on a vertical wall. It's compressible flow, and it's a two-phase problem. You have two boundary layers, one for the air-vapor mixture, and one for the condensate. The question I'm pondering is this...

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...

Hi. Do anybody here know how much and how quick a 50-100mm thick tempered glass plate of size 500mm * 500mm fully heated up within its bulk mass to a temperature of 60 degrees celcius looses it heat energy/temperature over time when surrounded by standing ambient air (20 degrees celcius)...

Homework Statement In Betty Crocker's cookbook, it is states that it takes 2h 45 min to roast a 3.2kg rib initially at 4.5 Celsius "rare" in an oven maintained at 163 Celsius. It is recommended that a meat thermometer be used to monitor the booking, and the rib is considered rare done with...

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...

Hi everyone, Ive come here not for an answer but to see if anyone can point me in the direction of a published book or equivilent to help me with some simple convection ideas. Im looking to basically outline the relationship between air velocity and heat in a forced convection situation. Its...

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!

I am working on a project that requires me to calculate the heat dissipation of a heatsink attached the a laser optic mirror. As the whole system is moving along a rail at 10m/s (average, 20m/s at fastest point) therefore forced convection takes place on the heatsink surface. I have modeled the...