Questions tagged [heat-conduction]

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1answer
139 views

Calculating the temperature of flowing gas in copper tube

A copper coil is immersed in a water bath. The water bath provides heat to heat the nitrogen gas when it passes through the copper coil. Nitrogen gas at room temperature is passed through the copper ...
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1answer
596 views

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same “dimensionality” and unit?

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same "dimensionality" and unit? $W/(mK)$ is thermal conductivity. $W/m^2$ is heat flow density related to one unit. $W/(m^2K)$ is the ...
19
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2answers
3k views

Why doesn't a mercury thermometer follow the rules of volume dilatation?

let's consider a classic mercury thermometer. I do not understand why it does not behave like a "normal" thermometer which exploits volume dilatation. In a normal thermometer, I'd say that ...
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5answers
144 views

Pressure=Heat? Else, Heat=Radiation?

A few days ago, I came up with this paradoxical conundrum: Let's say we have a gas enclosed in a container. Supplying heat to it will cause an increase in the (magnitude of?) vibration of gas ...
2
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1answer
35 views

Diffusion equation in terms of heat equation

I am solving a problem which goes like this: Solve the diffusion equation:$$\frac{\partial u}{\partial t}=\frac{\partial^{2} u}{\partial x^{2}}$$ for $t>0$ and $x \in > \mathbb{R}$, with ...
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0answers
24 views

Condensation of saturated vapor on subcooled droplet

Consider the process of condensation of vapor on falling subcooled droplet in the stagnant saturated vapor (neglect the vapor drag on droplet). What can be said about the relation between the droplet ...
8
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2answers
2k views

Heating cup in microwave?

I heated my milk cup in the microwave today and noticed that the cup was hot but not the handle. Even if I heat it too much , cups handle temperature remains the same. How is that possible?
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1answer
572 views

Calculating rate of heat loss through conduction and radiation

Calculate the rate at which a hollow cylinder with a heating element inside will lose heat, specifically through both conduction and radiation. My goal is to find the temperature inside this cylinder....
2
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1answer
50 views

Which heat capacity is used in the heat equation?

The heat equation is often written as $\frac{\partial T}{\partial t} = \frac{\kappa}{c} \nabla^2T$ where $\kappa$ is the thermal conductivity and $c$ is a heat capacity per volume. I often see $c$ ...
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1answer
158 views

Does a crushed ice cube and a regular ice cube have different potential energies?

For a question on an heat transfer experiment on melting ice cubes in water and measuring the temperature decrease in water, there was a question that asked: Suggest the effect, if any, of crushing ...
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0answers
34 views

Best color for pool cover [closed]

I couldn't find a stack* forum for pools, so I hope this is the next best place to post. I have an 18 foot diameter above ground pool in the north west, and I don't like the pool cover that came with ...
0
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1answer
42 views

Heat absorbed from a reservoir by a moving object [closed]

Imagine two bodies, say a body A with an infinite heat capacity(reservoir) and the another body B with some finite heat capacity($C = \alpha \ T_{B}(t) $). They come into direct contact with each ...
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0answers
58 views

How to obtain a solution for the following IBVP?

I am trying to solve the following advection-diffusion equation for transient flow conditions for radial flow. The governing equation is as follows. $$\frac{\partial T}{\partial t} = \frac{\partial^2 ...
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2answers
46 views

After sweating ,why do our body cool down faster under a fan?

The sweat on our body evaporate taking energy from our body in the form of heat.the temperature of our body decreases and we feel cool. Thus sweating cools down our body. Now why does our body cool ...
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0answers
15 views

Coupled solid-fluid heat transfer over a rectangular plate heated from the bottom (Boundary value problem)

I have the two-dimensional temperature Laplacian $(\nabla^2 T(x,y)=0)$ coupled with another fluid equation (which is one-dimensional). The Laplacian is defined over $x\in[0,L], y\in[0,l]$. On ...
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1answer
141 views

Calculate rate of heat gain of a steel chain in a campfire [closed]

Up front: I'm trying to be scientifically accurate about heating up a length of steel chain in a campfire to use as a surprise attack tactic in a D&D campaign, but I'm not sure I'm using the ...
2
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2answers
42 views

Does heat flow always in the direction of maximum decrease?

I was wondering if at a given gradient temperature heat could flow in any direction satisfying moving from a higher to a lower temperature. Or it can only flow in the direction of gradient? Consider a ...
12
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4answers
2k views

Why would frozen sausages defrost faster in water?

My mom uses frozen sausages for a soup. She defrosts frozen sausages by submerging them in water (room temperature I believe). She claims this makes them defrost faster. She learned this from some ...
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2answers
36 views

Will “stationary” air sorrounding a hot pipe from a wood stove act as insulation with a given time?

The inner pipe (colored in red) radiates considerable more heat than the current one so I'm planning on extending the more thermally conductive one so that it heats better. Will removing the outer ...
1
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1answer
33 views

Physical interpretation of the heat equation with variable coefficient

I would want to know what is the physical interpretation of the heat equation with variable coefficients such that: $$u_{t}-\frac{1}{1+t^2}u_{xx}=0$$ well, I think I got it, it means that the ...
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1answer
35 views

Heat transfer in glass top ranges

The "glass" in glass top ranges apparently has quite low heat conductivity as areas just a short distance from the heating element don't get so hot - especially compared to a metal surface which has ...
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0answers
17 views

Should I determine the wattage of my heater based on the heat conduction equation, or the specific heat capacity equation?

I know of the equation equating rate of heat flow to the product of a materials thermal conductivity, area of contact, temperature difference, divided by the thickness of the material. However, I ...
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0answers
38 views

Why does a cold glass container when heated in a microwave breaks down? But a container at a room temperature does not?

I have noticed that when I take some eatable kept in a glass container, out of the fridge, when they are already at a low temperature (around 3-4 degrees) and then try to heat it up in a microwave ...
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1answer
59 views

Definition of the rate of heat flow

According to Wikipedia the rate of heat flow is:$$\frac{\Delta Q}{\Delta t}=-kA\frac{\Delta T}{\Delta x}$$ Where to evaluate? I can't understand where we must evaluate this rate. In the hottest ...
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1answer
62 views

Why did my water boil “differently” this time?

Yesterday, I put a pot of water on the stove and set it to boil to make some pasta. I have done this many times but this time the boiling was qualitatively different than normal. Why would it be ...
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3answers
4k views

If steam and water, both at 100 °C, were exposed to a person's skin for a small time interval, which would result in a more severe burn?

Imagine that you had two boxes with of steam and water of equal mass, both at $100~^\circ\rm C$, and you decide to expose your left land to the steam and your right to the water for a short period of ...
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1answer
68 views

How do I set up the differential equations for the finite length iron stick heat diffusion?

Consider an iron cylinder. The heat doesn't go through the cylinder surface, but at the circular cross-section in the endpoints. The temperature of the surroundings is $15\ \mathrm{^\circ C}$. The ...
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1answer
37 views

Heat transfer from air (at ambient temp.) to a liquid in an open container [closed]

I’m designing a bath which should keep the temperature of the liquid inside (transformer oil) at a constant temperature (approx. 20 °C). I have calculated the amount of energy needed to heat up the ...
4
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4answers
83 views

Can a heated surface heat a solid on it above the temperature of the surface itself?

Let's say for example that I have a ceramic stove-top that heats to a measured maximum of $400\ \mathrm{^\circ F}$. I have a skillet of some unknown material that should not be heated above $400\ \...
2
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1answer
86 views

Transient heat conductivity with variable heat flux in 1D

I have a metallic block heated by a heat flux variable in time on one of its faces (let's assume that it is infinite in the other dimensions). I would like to compute the temperature over time at a ...
0
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1answer
73 views

Does fire caught by appliances causes short circuit [closed]

I know that short-circuit causes appliances to catch fire.But in my exam question was does the assertion is true I think although each of wire has insulation but they are separated by a distance at ...
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1answer
48 views

Does Earth's core have a heat sink and does it need one? [closed]

Pardon a question from a complete physics noob. I know only very basic thermodynamics and if my question is completely ridiculous, I apologize. I've heard a very interesting, yet very questionable "...
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0answers
20 views

Induction cooker

I was using an induction cooker and I kept my steel utensil empty on it and switched it on. After some time the bottom part of it became red hot but the upper part of it was completely cool. Why does ...
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1answer
68 views

Confusion in first law of thermodynamics

Our teacher while explaining first law of thermodynamics showed us an example of a piston inside a chamber. He said when heat is applied the particles move, i.e the kinetic energy increases. Due to ...
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0answers
38 views

How to properly implement Newton Cooling in FTCS Heat Equation

I am attempting to model the temperature in 2D plate using the FTCS scheme for the heat equation. The plate is finite, and discretized squarely. I do not want the temperature fixed at the edges. ...
2
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1answer
106 views

What would the surface temperature of the Earth be without the Sun? [closed]

If the Sun would not heat the earth, and never had heated it in the past, its surface would only be heated from the inside. What would be the current temperature of the surface?
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1answer
16 views

Heat Transport in humidity control

PROBLEM 6.11 A humidity box for laboratory use is constructed from panes of window glass of thickness 4 mm. The temperature inside the box is maintained at 90°C and the ambient room temperature is 25℃·...
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2answers
59 views

Temperature and kinetic energy of a particle

We know that heating an object makes the atoms in it vibrate. But in case of ideal gases we say that heating them increases their kinetic energy. But how does kinetic energy increase and not ...
2
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2answers
105 views

At what speed does heat flow in materials?

When we heat one end of an iron rod on the stove, it takes a considerable time for the other end to be heated to the same temperature as the first end. On the other hand, as we know, the atomic ...
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0answers
28 views

How to calculate the heat energy lost to two steel electrodes in contact with a piece of heated Titanium in a Vacuum

Say within a vacuum chamber I have two steel electrodes in contact with 0.0006 m^2 of Titanium heated to a temperature of 1,800 degrees Kelvin. How would I calculate the heat energy lost via contact ...
0
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1answer
53 views

I need an explanation of insulation

Clothes reduce the heat loss to keep a person warm. But if the person is always producing more heat than the clothes are losing it, his temperature will rise indefinitely. Is it because as the object ...
0
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1answer
56 views

Thermal Conduction through 1D rod having non-uniform cross sectional area

I recently came across the formula $Q=kA(T_2-T_1 )t/l$. I have a question regarding the interpretation of the formula. 1.)Does Q refer to the amount of heat that flows through a cross sectional area ...
0
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1answer
73 views

Method of images for infinite cylinder between two parallel surfaces, one insulating and the other constant temperature

Trying to solve for temperature distribution of a infinite cylinder of radius $R$ of uniform time independent heat generation [$P$] = W$\cdot$m$^{-3}$ suspended between two planes a distance $d$ apart,...
42
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7answers
5k views

Bush fires and heat waves, the real mechanics?

Like many others, I have been following the sad development of the bush/forest fires in Australia recently. A claim that gets repeated is that one of the contributors to this blaze is the ongoing >45°...
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0answers
19 views

Temperature difference of thermoelastic bodies [closed]

Let $B$ be a "very thin" tridimensional deformable body of the form below. Let $T_0$ be the temperature of $B$ in the reference state. Let $T(x,y,z)$ be the temperature at a point $(x,y,z)$ of the ...
2
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2answers
739 views

Calculating heat loss to surroundings from a cube suspended in air?

If you have a cube that is suspended in the middle of the air, how would you calculate the heat loss to its surroundings? For this example, I am assuming the following: Dimensions: 1m×1m×1m ...
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2answers
106 views

Rate of conductive heat transfer at a boundary between two different materials

I have one block of material 1, and one block of material 2. They are in contact with each other, sharing an interface of area A. Material 1 behaves as a lumped capacitance, with temperature T1(t). ...
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1answer
57 views

What is thermal conduction fundamentally?

Is conduction at the atomic level simply electromagnetic energy (photon) transfer, coupled with momentum transferred during collisions? Can conduction be summed up as thermal radiation + momentum ...
1
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1answer
90 views

How does the heat equation model concrete problems accurately

Let's just say that I am a beginning practitioner of mathematics who never gave physics a serious shot and looking to get an intuition of how partial differential equation works in relation to the ...
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1answer
336 views

Microscopic level - What happen to the particles in a heat transfer through conduction?

So on a macroscopic level, there is physical contact and the heat energy is being transferred from the higher temp. to lower temp. But what about in a microscopic level, what's going on? As far as I ...