1
vote
3answers
56 views

Convective heat transfer coeficient equation

I am attempting to model a situation, in which a sphere of some material of identifiable thermal properties is receiving heat at a constant rate. And that material is coming into equilibrium with the ...
0
votes
1answer
86 views

How hot does the upstairs need to be before it will heat the basement through convection?

During the winter we keep the basement door closed so that the cold air from upstairs won't flow into the basement. Then we heat the basement and the upstairs gets heated partially by conduction ...
0
votes
0answers
10 views

Does transverse flow always assist in mixed convection?

I am dealing with both natural convection and transverse forced convection over a flat plate. There are 4 different situations: Upward-facing cold plate Downward facing cold plate Upward facing hot ...
0
votes
0answers
71 views

Determine pipe outlet temperature without length?

Let's say I am flowing a fluid through a pipe that has a constant surface temperature. Is it possible to determine the heat flux on the inner surface without knowing the pipe's length when the only ...
0
votes
0answers
51 views

Convective heat transfer coefficient for counter-current flow

This is not a counter-current heat exchanger. It is two phases, Gas and Water, flow in one flow path but in opposite direction. I have found many source doing analysis on flow pattern of the ...
2
votes
3answers
726 views

Improving our homemade hot tub design?

My brother and I built a wood burning, convection based, thermal circulating hot-tub. (With and oxyacetylene torch, lots of 1.5" pipe, a brake drum, and a thirty year old jacuzzi). Our design is ...
2
votes
4answers
374 views

Boiling Order (Thermodynamics) [closed]

Three pots made of the same material are placed one inside the other and all pots are filled with water to the same level. If heat is applied to the bottom of the outermost pot what will be the ...
0
votes
0answers
35 views

Transient conduction - Biot number with irradiation?

I understand that the Biot number is essentially the ratio of the convective effects to the conductive effects in transient conduction but what if there is some sort of radiation from a heat source ...
0
votes
2answers
1k views

Realistic calculation of heat loss for pipe

Good day everyone, I am new on this site and I hope to find here help, since I am not going anywhere with the literature I have found. I try to calculate realistically the heat loss of a hot, ...
0
votes
0answers
97 views

Characteristic length of differential element of cylinder surface?

I am trying to find the Nusselt number for a small element of the outside of a cylinder that has a height of $Delta z$. I found the average Grashof number of a surface as $$Gr_{L}=\frac{\beta \rho ...
60
votes
12answers
7k views

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 ...
1
vote
1answer
272 views

Is the convective heat coefficient always dependent on heat flux and delta T?

I'm having a difficult discussion with a colleague because I'm running heat flow simulations for a small heater (5 mm^2 area), and I insist that if we're going to run more electrical power through the ...
-1
votes
1answer
109 views

Heat Sink Design-Choice of Material [closed]

I am currently designing a heat sink for OPA 549. Among the many considerations, for example, the choice of material, the geometry of heat sink, the design of fins and all the parameters that come ...
1
vote
1answer
415 views

Do metals generally lose more heat by convection than non-metals?

I've been experimenting with radiative cooling lately and in my mind convection is always an enemy (especially forced convection since the modules are outdoors). Looking at Newton's law of cooling, ...
0
votes
1answer
267 views

What happens to pipe outlet temperature here?

I have a fluid flowing through a pipe in the ocean and there is heat transfer from the ocean to the fluid in the pipe. I prepared a simulation and the results show that if I increase the mass flow ...
1
vote
3answers
733 views

What's the physical difference between a convective heater and an infrared heater?

Could someone please explain why there are 2 types of space heaters-- one that is convective and one that is infrared? Why does the first one not radiate and why does the second one not heat the air? ...
3
votes
1answer
262 views

Rayleigh-Benard Convection

I found this nice paper about RB convection. However I am confused by what is going on page 6. In particular why we are suddenly using Helmholtz equation to find spatially periodic solutions. Aren't ...
0
votes
2answers
6k views

What is the characteristic length of a cylinder

I have a cold cylinder that is submerged in hot water and I need to find the convective heat transfer coefficient. I can do the whole process but I am stuck finding the characteristic length. I found ...
11
votes
2answers
15k views

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 ...
1
vote
1answer
502 views

How would I calculate the convection coefficient in transient convection?

So I have faced a problem dealing with transient conduction and I need a little help with the problem solving concepts. I need to determine how long it would take to reach the final temperature but I ...
2
votes
2answers
209 views

How would I go about solving this transient convection problem if the mean fluid temperature is constantly changing?

Let's say I have a ceramic slab on a conveyor belt that is initially at $450\,^{\circ}\mathrm{C}$ and there is air being blown over it at a speed of $35 \frac{m}{s}$ with an ambient temperature of ...
3
votes
2answers
1k views

Why is oil a poor conductor of heat?

Why is oil a poor conductor of heat? Does it help in insulation?
1
vote
1answer
317 views

Per unit area, is there more heat transfer through the open top of a mug or the side walls?

I had a mug of hot coffee cool too rapidly for my liking the other day, which made me wonder what was the greater contributor to heat loss for a typical open-top ceramic mug: the open top, the walls, ...
2
votes
1answer
1k views

Finding electric power generated using heat transfer

I'm working through an example I have been given to study. Suppose I have a 2m X 4m photovoltaic panel on my roof that is irradiated with a solar flux of $G_s = 700W/m^2$. Given: $\alpha_s = 0.83$ ...
2
votes
1answer
2k views

How does smoke move in the air and how can I direct it so it will go to a place I want it to go?

Let's assume a close room with 1-2 people who only one of them smoking cigarette. What is the equation describe the smoking spreading? is it diffusion? what are the parameters is so? Is there a ...
1
vote
1answer
986 views

In what situations do I use the characteristic length of a fin to find the surface area?

So I'm learning about fins in heat transfer and it seems that there are two separate formulas for the surface area of a rectangular fin of length L, width w and thickness t. The fin is attached to a ...
3
votes
3answers
632 views

What is the most efficient way to use hand dryer?

What's the most efficient way to place your hands under the hand dryer? Let's assume that dryer creates simple downward flow of hot air. Here are some examples:
5
votes
5answers
2k views

Is there an equation for convective heat transfer?

Is there an equation I can use to calculate the temperature (as a function of time) of an object which is gaining or losing heat by convection? Or equivalently, the rate of energy transfer from the ...