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0
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1answer
22 views

At what rate does a wet clothing decrease the temperature of a human body?

The question is required for my project, but it is frankly too hard for me... The variables that I consider are: Human Body: 36.5(C) Air: 20(C) Sunlight Intensity: 1,368(W/m^2) Wind Speed: 20(km/hr) (...
-3
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2answers
57 views

Which one is better at keeping you warm? [closed]

Does Glass feel warmer during winter when you keep your feet on it or Wood?
-1
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0answers
26 views

Would a black copper bowl full of water in a hot, sunny room absorb enough heat to evaporate the water?

I'm looking at making my conservatory more humid, it gets a lot of sun and gets very, very hot. If I were to put a black copper bowl in the room full of water would this be a good metal for ...
5
votes
1answer
50 views

Why do electrically conductive materials tend to be thermally conductive?

It's hard finding substances that are good insulators of one and conductive of the other. Why the correlation? And why do some materials not have this correlation?
3
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1answer
74 views

Why thermal conductivity increases with temperature?

what is the molecular mechanism with which thermal conductivity increases by increasing temperature? at least for metals? I know that heat increases the oscillations of the atoms in the crystal. But ...
4
votes
2answers
92 views

Heat distribution in a long cylindrical electrical resistive element

I want to know what the maximum temperature will be within a heating element. Quite a few assumptions can be made, such as constant thermal conductivity, constant electrical resistivity, and assume ...
0
votes
1answer
41 views

Thermodynamics - Change in temperature based on time

Hello Physics Stack Exchange, This is my first post on this forum, please correct me on any semantic mistakes I may make. Recently in my physics class we did a lab on Heat Capacity, where we had a ...
0
votes
2answers
26 views

Discrepancy between the rate of heat flow

I'm in a introductory college physics class, and my professor recently gave us this formula for the rate of heat flow: $\frac{dQ}{dt} = \frac{A \Delta T}{R_{factor}}$ where $R_{factor}$ is $\frac{L}{...
2
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3answers
153 views

Why engines don't melt?

The temperatures of internal combustion engines are well above the melting points of the component materials. For example, temperatures can reach 2200° C whereas the melting point of aluminium is 659°...
0
votes
1answer
30 views

Convective heat transfer coefficients - how do you calculate them?

How do you calculate (or otherwise determine) h_i and h_o (convective heat transfer coefficients) for a heat exchanger? Standard thermodynamics equation below for reference. My specific situation ...
-1
votes
3answers
114 views

Bird on electric wire: theoretical distance between the two bird legs [closed]

Hey guys, please someone help me with this exercise :) For our exercise, assume that the bird’s body resistance (from leg to leg) is 50kΩ. Given is a high voltage power line with a current of 100A ...
0
votes
0answers
18 views

Systems with these temperature dependence of thermal-conductivity

I want to find out examples for systems (of any kind) in which the temperature dependence of thermal-conductivity($\kappa_{T}$) is of type- \begin{equation} T^{-\alpha}~~~~~ where ~~~~~\alpha>0 \...
2
votes
1answer
54 views

Localized Phonon Vibrational Modes and Thermal Conductivity

I chanced upon this 1D chain Mass Impurity model: At the end of all the derivations, it concludes that Case 1: $ 0 < M_0 < M$ The impurity is lighter than the host atoms. The frequencies ...
0
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1answer
32 views

Is thermal transfer in a vacuum proportional to temperature difference?

I would have thought that heat dissipation was proportional to temperature difference, especially in a vacuum. Is this true?
1
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0answers
19 views

How does heat conduction differ from convection? [closed]

How does heat conduction differ from convection?
3
votes
2answers
57 views

Why are metals worse conductors when heated?

When metals, (such as in circuits), are heated, their ability to conduct electric current is hampered. Why is this? Does the transition towards liquid disrupt a metal's ability to conduct, or is ...
0
votes
1answer
37 views

Relationship between thermal conductivity and reaching the steady temperature

The diagram is for three materials with 3 different thermal conductivities, i think the material with higher thermal conductivity is the number 1 because it transfers the heat much better so it gets ...
0
votes
1answer
42 views

Transfer of heat from ice to water in a beaker

How does the transfer of heat takes place from ice below 0 degree celcius to water at room temperature? Does it take place by conduction? Does temperature of water rises uniformly throughout or it ...
1
vote
1answer
91 views

Help me solve a heat conduction/emission transfer problem. Mathematica has failed me

My problem: A thin-walled tube (length $L$, diameter $D$ and wall thickness $t \ll D$) is in a vacuum. It is held on one end (at $x=0$) by a heat source at constant temperature $T(0)=T_0$. The only ...
0
votes
1answer
20 views
0
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1answer
77 views

Drift velocity of electrons in a conductor

How does the drift velocity of electrons in a conductor depend on the temperature? I have two contradicting views for this. First, we can say that increasing the temperature of the conductor will ...
0
votes
2answers
149 views

relationship between pressure and thermal conductivity

Using a kinetic model for gases, is it possible to derive a relationship between pressure and thermal conductivity? From what I have read, I thought pressure was independent of thermal conductivity? ...
0
votes
1answer
21 views

Estimating fraction of radiant energy absorbed by a metal

I have a couple of texts on thermodynamics and radiant energy but am finding it difficult to figure out from these how energy absorption and reflection work. The area of interest is heating ferrous ...
0
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0answers
17 views

What's the simplest, first order way to calculate the temperature change in this scenario?

I am trying to model this experiment in a simple (i.e., relatively analytic, non-computational) way. I have a little square of a thin film (10s of nanometers thin) of material A, on a relatively ...
1
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1answer
29 views

thermal fatigue and thermal conductivity

Today I argued that heating and cooling a metal many times will affect its thermal conductivity. My idea is that heating and cooling, ie. thermal fatigue, will affect longterm the the microstructure ...
0
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3answers
85 views

Thermodynamics at the stoves, cooking problem

I was wondering about a daily question with respect upon heat, time and thermodynamics "made easy". Supposing I put a pot on the stove (we can say without losing so much that the pot is a cylindrical ...
0
votes
1answer
53 views

Conduction problem [closed]

A hot reservoir with a temperature of $782 K$ is $0.56 m$ away from a cold reservoir with a temperature of $331 K$. The two reservoirs are insulated from each other except for a rod of brass ($k = 109 ...
0
votes
1answer
58 views

Why the 3D heat equation is $\frac{\partial u}{\partial t}=\alpha\nabla^2u$ [closed]

Why the 3D heat equation is $$\frac{\partial u}{\partial t}=\alpha\nabla^2u=\alpha\left(\frac{\partial^2 u}{\partial x^2}+\frac{\partial^2 u}{\partial y^2}+\frac{\partial^2 u}{\partial z^2}\right)?$$ ...
0
votes
1answer
41 views

Anomalous expansion of water when heated

In one question I found that when water was heated from 0°C to 15°C then the volume 1st decreases and then increases why is that so ?
3
votes
1answer
291 views

Why are wooden houses warmer than concrete ones in cold regions?

Why are wooden houses warmer than concrete ones in cold regions? I went looking for data and I saw that both have similar emissivity and similar conductivity. Thus I am confused. Moreover, the ...
0
votes
1answer
71 views

Will throwing oil on snow help it melt faster (significantly)? [closed]

The main thing that melts snow is the sun. Indeed, without the sun, the air itself would eventually turn to snow. The problem is, the sun melts snow inefficiently. The sun emits radiation (a lot of ...
0
votes
0answers
74 views

Heat Losses to furnaces

I am looking in to the thermal efficiency of a furnace vessel. I am wanting to get a full, or at least better, understanding on the calculations needed to look at the thermal efficiency. So I know ...
0
votes
0answers
39 views

How is Thermal Design Power (TDP) related to Surface Power Density (SPD)

Although this question is kind of IT related I'm interested into the actual physical backgrounds and thus posting it here. I know that TDP is an indicator for dimension of the thermal dissipation ...
0
votes
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 ...
1
vote
0answers
58 views

At the lambda point, why does specific heat capacity tend to infinity?

The specific heat capacity is the energy required to raise the temperature of unity mass by 1K, if at the lambda point all the bosons occupy the lowest quantum state, shouldn’t the specific heat ...
1
vote
1answer
36 views

How does conduction happen?

I'd like to ask you how does conduction happen ? I mean, the atoms vibrating more hits the less vibrating atoms and gives energy. But how is that energy transferred ? For atoms to collide they must be ...
1
vote
2answers
48 views

Effect of Particle Mass on Thermal Conductivity

Fouriers law of thermal conductivity is $$ \vec{q} = -k\nabla T $$ where $q$ is the heat flux, $k$ is the thermal conductivity. Mass does not seem to appear in the equation. So I'm wondering what ...
3
votes
2answers
163 views

Different results for thermal resistances using different methods

A system is set up which is composed of a cylinder with hemispheres on either ends. The length of the cylinder is l and inner and outer radii of cylinder and hemisphere are $R_i$ and $R_f$. The ...
0
votes
1answer
91 views

how can different shapes of thermometer bulbs effect response to temperature changes?

Two thermometers are constructed in the same way except that one has a spherical bulb and the one, cylindrical. Which one will respond quickly to temperature changes and why?
1
vote
1answer
67 views

What is the coefficient of volumetric expansion of water? [closed]

What exactly is coefficient volumetric expansion? Is it $\gamma\,\Delta T$? Since water has maximum density at 4 C, is $\gamma=4\,{\rm C}^\circ$?
3
votes
2answers
101 views

Is sun a black body? [duplicate]

My teacher told me that sun is a black body but after reading at various sites whre they say that sun is not a black body but has black body radiations because it cannot absorb all radiations.
0
votes
0answers
41 views

Thermal conductivity of a binary gas mixture

I want to estimate the thermal conductivity of binary gas mixture, say water vapor+nitrogen. I assume the mixture as ideal gas. The molar fraction and thermal conductivities of the components are ...
2
votes
2answers
288 views

On a molecular level, how does heat transfer take place?

When an ice molecule hits a water molecule, the water molecule adds kinetic energy to the ice molecule. Why do the water molecules lose kinetic energy? In other words, why does heat like to go where ...
6
votes
2answers
198 views

Is the thermal conductivity of metals affected by magnetic fields?

Especially for a ferromagnet a magnetic field should have a field-induced band shift in the density of states but I wonder if this shift is big enough to be significant and affect the thermal ...
0
votes
0answers
22 views

Heat transfer in liquid helium channel connected to “infinite” reservoir

I am trying to solve the temperature distribution in liquid helium using numerical analysis (OpenFOAM for those who are familiar with it). One part of the fluid is contained in a narrow channel, one ...
2
votes
1answer
55 views

Thermal Interaction in a Vacuum

In order for a thermal interaction, or heat energy transfer, to take place, two bodies must be in contact. Whether this be the particles of air in contact with your skin to make you feel warm or cold, ...
0
votes
0answers
31 views

Solving for temperature at the source, given a distant measurement

Let me start of by stating that I am not a physicist, so this question may appear trivial to those more enlightened than me. My problem is as follows: I have an object at $x = 0$ and at some initial ...
0
votes
0answers
41 views

Kubo formula for thermopower (seebeck coefficient)

I have a long-standing puzzle about the Kubo formula relating to the thermopower defined as S=L_{21}/L_{11}. Here L_{ij} are elements a 2 × 2 matrix of transport coefficients, with J_E=L_{11} E - L_{...
0
votes
0answers
38 views

How do you go from the heat equation to calculate the steady state heat transfer to the end of a rod?

Heat equation: $$ k\nabla \cdot \nabla T + \dot{q} = \rho C_p\frac{\partial T}{\partial t} $$ I want to know given a rod or a cylinder of material, but lets start simply with a rectangular rod, and ...
1
vote
1answer
82 views

How to find the variation in temperature at a certain point inside a body undergoing heat transfer via conduction?

I am trying to find a way with which I can find out the temperature of a certain point inside a body undergoing thermal conduction. I understand that this might not be very simple to calculate since ...