transport mechanism involving bulk motion of a medium

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1answer
52 views

Buoyancy and natural convection in a stratified water tank

I'm working on a simple calculation-model for a hot-water-storage. At the moment I'm stuck on implementing natural convection. To calculate the temperature I've implemented a simple 1D-model in ...
4
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0answers
90 views

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 blow directly over the surface of the water (kept in a ...
0
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1answer
37 views

Why does increasing heat conductivity decrease Nusselt number?

Normally we expect that when heat conductivity(k) increases heat transfer is also increases. But for fluids increasing k decreases Nusselt number. My senses tell that using high conductive fluid cause ...
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0answers
29 views

Calculate Temperature change in a solid due to resistive heating

Trying to calculate temperature increase in a solid due to resistive heating by a current flow, is this along the right lines? First I have calculated resistance due to resistivity, then calculated ...
0
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0answers
18 views

Inductance heating, Temp Change [duplicate]

I am trying to find the temperature increase of a solid(copper) in a gas (air) due to an electric current passing through the solid (inductance). I need to encompass any temperature losses from the ...
1
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0answers
54 views

Maximum temperature possible on earth

What is maximum temperature that can we have on earth on a single day? Lets say an air mass is static over an area and there is no way for air mass to move, sun warming it up would increase ...
2
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2answers
70 views

Thermodynamics : Heat transfer : Conduction or convection?

I have an hot object, that is place in a room of 20°C. My goal is to be able to estimate how warm the object will be in T seconds. To be able to do that, I must first understand what is really ...
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0answers
26 views

Water in pot with a heat source beneath it to boil it, does the water move?

I mean if there is there heat transfer by convection in the water? since convection requires motion. if it moves, then how can i determine the velocity of the water?
3
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1answer
112 views

What causes the differential rotation of the Sun?

I have read the explanation in Wikipedia, but the problem is that because I'm a beginner in physics, I don't quite understand what more than half of the words mean! Here is the explanation from ...
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1answer
20 views
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19 views

How much power is being actually delivered by an electric heater to a cooking pan?

I've been doing experiments on an electric heater heating a cooking pan filled with 2 litres of water, from 20°C to 70°C; now I'm trying to draw a theoretical heat transfer model thath should match ...
0
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1answer
14 views

Which are the best books I can refer for turbulent heat transfer and its computation?

I am a graduate student. I wanted to do computation on heat transfer problem mainly heat convection. I am working on turbulent regime. Can you kindly suggest some good books so that I can get ...
0
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0answers
38 views

What is the use of thermal boundary layer and velocity boundary layer?

In heat transfer by convection, why must we show the thermal boundary layer and the velocity boundary layer. What do they signify? Also how are these terms related to the Prandtl number? And what is ...
1
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1answer
89 views

Is there a difference between solid-to-fluid convection and fluid-to-fluid convection?

I found an online calculator relating to convective heat transfer, but the calculator's description says it's for heat transfer between a solid surface and a moving fluid. However, the definitions I'...
0
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0answers
29 views

Extension of the advection diffusion equation with diffusion perpendicular to the flow

Assume you model particle flow in fluid in a cylinder by an advection-diffusion equation, thus taking into account both diffusion and bulk flow. What would happen to the model if you would, at some ...
0
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1answer
39 views

When does heat conduction become convection?

Okay, I have a hard time wrapping my head around something, I think, pretty basic. For a little hobby project of mine I was making a fermentation-box for beer brewing allowing me to accurately ...
0
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1answer
94 views

flat plate isoflux convection - how to calculate temperature

I am an engineer trying to design a simple 1D program for evaluating the temperatures of a multi-layer heatsink that includes convection and radiation heat transfer from the external surface. For a ...
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2answers
42 views

Hot Object In a Cooler Space [closed]

How would you calculate the heat given by an object that is hotter than its surroundings? I know there's Newton's Cooling Law, but what about any heat given off by radiation? Are these additive ...
0
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1answer
51 views

Time dependent heating of a conductor

I have a conductor that's being heated with current. I want to know the temperature of the conductor Steady state soultion is: $$P_{\text{generated}}=W_{\text{conduction}}+W_{\text{convection}}+W_{...
0
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0answers
97 views

Heat transfer through convection in human body

How does the heat transfer takes place in human body through convection in these two situations. 1) when environment temperature is less than body core temperature($37^0C)$, say it is around $25^0C$. ...
0
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1answer
94 views

Convective heat transfer

At y = 0 It is said that the heat is transferred by conduction because the fluid has a velocity equal to 0 (no-slip conditions). But the temperature of the fluid for y=0 is equal to Ts(temperature of ...
0
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0answers
46 views

How can I get the boundary and initial conditions of the convection–diffusion equation consistant?

I want to solve the 1D convection–diffusion equation. The boundary conditions are a flux in from the bottom and a flux out on the top. Furthermore I want no concentration inside at the beginning. I ...
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2answers
143 views

Heat loss via convection

Suppose I have a glass container (trough) and I want to heat the water inside. I put it on a hot plate. Now, even though the hot plate is at $110\,^{\circ}C$, the liquid only reaches $50\,^{\circ}C$. ...
0
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1answer
662 views

Convective boundary condition

Consider a fluid over a sheet which is placed horizontally along the x-axis. The lower face of the sheet is in contact with another fluid at temperature $T_f$ ( it is heating the sheet). The sheet is ...
5
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0answers
186 views

Numerical Solution of the Propagation-Dispersion equation

I have asked this question on Computational Science and also on Mathoverflow, but no satisfactory answers so far. I thought maybe the physics community could shed some insight on the issue. I am ...
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2answers
55 views

Is air infiltration a type of convective heat transfer (convection)

I have a building / physics question... A major source of heat loss in homes and buildings is infiltration through cracks (warm air from inside seeping out). Wondering if this falls in the category ...
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0answers
39 views

Forced convection: temperature gradient in conical pipe

My situation involves a conical pipe of known dimensions and material composition. Warmer-than-ambient air is added to the small end at a steady, known flow rate. I'm hoping for a way to estimate ...
0
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0answers
96 views

Heat flow through a pipe

I have a pipe, in which a cooling medium flows through it. I would like to know the temperature of the cooling medium at different lengths of the pipe. Is there an equation to relate the length and ...
21
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1answer
2k views

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 ...
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0answers
14 views

Vertical wall at 3 different temperatures - do the same natural convection coefficient correlations apply?

I have an vertical enclosure that consists of 3 shelves, each with its own temperature and are thermally isolated from each other. We will call the shelves A, B, and C with A being the base shelf. The ...
0
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0answers
47 views

How complex is an energy balance for this problem?

Let's say I have an enclosed room in the shape of a box with forced airflow on the outer walls at an ambient temperature. Each end of the room (forward and rear) has a vent that ducts in warm air to ...
10
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2answers
425 views

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 ...
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3answers
3k views

Is heat from a stovetop, transfered through convection, radiation or conduction?

It doesn't appear to be convection, as there are no moving objects (or are there); probably not radiation (?), so it is conduction? I really don't know much about heat transfer and thermodynamics, ...
0
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1answer
94 views

Series of parallel thermal resistance connection for this enclosure?

Let's say that I have an 2D enclosure in the shape of a pyramid with unequal areas for the faces and I am looking to determine in the inside air temperature. The parameters I know are the outer and ...
1
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1answer
132 views

Why Benard cells are usually hexagonal?

Solution of equations of convection (hydrodynamics equations in Boussinesq approximation) involves existence of convective cells, so-called Benard cells. They are represented by superposition of ...
6
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4answers
11k views

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?
2
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1answer
58 views

When I'm in a warm room how much of the warmth I feel is due to radiation from surfaces?

Say I'm in a room heated to 23C, once the temperature is in balance all the objects will also be 23C and radiating heat towards me. How much of the warmth I feel is due to this radiation, and how much ...
0
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3answers
80 views

Photon walk in stars with convection

I'm having trouble figuring this out. I've read, that when photons are created via nuclear processes inside a star, it can take about 1 million years for photons to actually reach the surface of a ...
1
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1answer
691 views

Heat transfer between the bulk of the fluid inside the pipe and the pipe external surface

In an article from Wikipedia about heat transfer coefficients in the section Combining heat transfer coefficients there is an equation which describes the rate of heat transfer between the bulk of the ...
1
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1answer
516 views

Rate of Temperature Change due to Heat addition

I might be wrong but I will give a little background leading to my question. I am trying to calculate the heat generation in the advection-diffusion equation for heat generation due to friction by ...
2
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2answers
110 views

How stable are Benard Cells when the thermal gradient begins decreasing?

I've found lots of information on the formation of Benard Cells and convection currents but very little information about what happens to the self-organized structures when the energy gradient being ...
0
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0answers
236 views

What is the minimum volume in which, for a given temperature difference $\Delta T$, natural convection would occur?

I'm trying to figure out if convection will occur in a plastic bottle slice and what length of slice would be optimal to achieve high R value transparent insulation on the cheap. The bottle slice is ...
1
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1answer
2k views

Will a liquid boil quicker if it is stirred versus if it is not stirred

Will the whole liquid boil quicker on a stove-top if it stirred versus if not stirred? What should be the frequency of stirring to get to boiling point quickly? please explain your hypotheses with ...
2
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0answers
37 views

Vanishing viscosity in eqn. of heat transfer for free convection: on what argument?

In Landau's and Lifshitz' Fluid Mechanics on the derivation of the equation of heat transfer for free convection p. 218, they write In the thermal conduction equation (50.2), the viscosity term ...
0
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1answer
130 views

At what gap width between two plates does convection not occur?

Does the Grashof number lead to the answer? The Wikipedia article (https://en.wikipedia.org/wiki/Grashof_number) yields an equation for vertical plates $$Gr_L = \frac{g\beta(T_s-T_\infty L^3)}{\nu^2}$...
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4answers
266 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 ...
6
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1answer
442 views

How does the windchill factor exist above 98.6 degrees?

As I understand it, the explanation of the windchill factor goes like this: Your body is warmer than the air around it, therefore it loses a certain amount of heat to the air. This warms up the ...
0
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1answer
454 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 ...
2
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2answers
435 views

Which temperature to evaluate fluid properties in pipe?

I am always confused about which temperature to evaluate fluid properties at. Let's say I have a helical pipe and I know the inlet temperature, outlet temperature, and surface temperature and the ...
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0answers
510 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 ...