# Questions tagged [thermal-conductivity]

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### Thermal contraction for cooling

I've calculated by separation of variables function of temperature $T(x,y,z,t)$ for a cooling cube. I wanted to know how much the cube will contract in one dimension after 10 second of cooling, during ...
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### Does adding cold water to evaporative air coolers actually produce colder air?

Or should it be the other way around, because hotter water evaporates easier than cold water? I know this sounds stupid, so just hear me out. I use an evaporative cooler and add normal room ...
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### Is 1D diffusion equivalent to diffusion in symmetrical coordinates?

Say you are modelling heat diffusion from hot air into a sphere. The thermal conductivity is the same at all positions on the sphere. Using the 1D diffusion equation, the temperature of the sphere is ...
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### 3-Omega method outside of um scale

Currently being fascinated by the 3-Omega method for measuring thermal conductivity. As a hobbyist, I'm currently not capable of making the sensors directly on the samples I would like to test. After ...
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### Relighting a candle from its smoke, and being burned?

Having been extinguished, a candle can be relit from the resulting trail of smoke, even from meters away. However despite this apparently high level of heat, paper, bystanders, etc… are never ...
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### Coefficient of thermal expansion [closed]

Is the coefficient of thermal expansion of a particular material under constant pressure constant?
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### Pressure Drop in a Pipe due to Pressure Increase

I'm trying to calculate the pressure/temperature change in a pipe due to heating. Basically, assume there's a pipe, the pipe wall is at an increased temperature, how to calculate the pressure, ...
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### Why do we cool water with ice? [closed]

I've came up with the following question: Why do we cool water with ice rather than with steel given that the last one has a bigger thermal conductivity?
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### Difficulty in theoretical understanding of Newton's law of cooling

Newton’s law of cooling states that the rate of heat loss of a body is directly proportional to the difference between the body’s temperature and that of the surroundings when there is a breeze. I can ...
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### How do I calculate equilibrium temperature of a pot of water with some food in it, knowing only the equilibrium temperature of the pot of water? [closed]

Say I have a pot with 3L water on a stovetop, at an equilibrium temperature of 75ºC. I then add 1kg of meat at 20ºC to it. How do I calculate the final equilibrium temperature I should expect the pot'...
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### Heat Transfer on boiling water

Let's say I'll boil water on the stove from 25°C to 100°C, what heat transfer happens? Is it conduction (heat warms up the pot), or is it convection (causes water molecules to move away from the ...
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### Analytical solution of the thermal conductivity equation [closed]

What is the exact analytical solution of a 1D thermal conductivity PDE: $\dfrac{\partial T}{\partial t} = \alpha\cdot \dfrac{\partial^2 T}{\partial x^2}$, where $T$ = temperature, $\alpha$ = thermal ...
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### Where would you sit? [closed]

Suppose on a summer afternoon, you have two chairs one made of steel and other of wood. Which one is better to sit on if you prefer colder one, provided they are at the same temperature?Would your ...
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### Why heat flow perpendicular to the isothermal surface?

I was reading Feynman-Leighton-Sands 's physics lecture note in Volume 2 chapter 2 when deducing the equation $$h = -k\ \text{grad}T$$ It seems we use the assumption that heat flow orthogonal to the ...
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### Characteristic timescale of a can of beer?

Modelling a 440 ml can of beer by Newton's law of cooling, the temperature difference between the can and its surroundings (e.g. a fridge) decays exponentially in time at a rate determined by the e-...
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### What is the temperature profile of hot and cold fluids for a double pipe parallel flow heat exchanger?

In books, they just mention the temperature profile is exponential. Can someone help me come up with the exact temperature profile (the relation) for the hot and cold fluids in a double pipe parallel ...
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### Is it wrong to derive Log mean temperature difference (LMTD) of a Heat Exchanger, this way?

I tried deriving the LMTD of a parallel flow double pipe heat exchanger by first finding the temperature profiles of the hot and cold fluid and then averaging them over the entire length of the Heat ...
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### While determining LMTD for a heat exchanger do we assume, the tube wall to be at a constant temperature (no variation along radial direction)?

The derivation of Log Mean Temperature Difference (LMTD) for a Heat exchanger at preliminary level makes some assumptions like, constant specific heats, steady state operation, no changes in kinetic ...
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### Heating of a metal rod

On heating a metal rod from one end ,after sometime it reaches a steady state. Is the temperature of the end directly receiving the heat is equivalent to the temperature of the heat source ? Even in ...
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### Effect of coloring on emissivity at temperatures below 150C?

I'm working on Aluminum/Copper heat sink design optimization and came across this thought. The heat source on which the heat sink is going to be placed is approx 100C. Forced convection is absent, so ...
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### Heat diffusion in an oven

I have this problem where I am preheating an oven to reach $n^\circ$. So lets say within the oven there's a heating element at the bottom, which in turn heats up the rest of the oven. Assuming that ...
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### Is there a Relationship between thermal Hall conductivity and coplanar/non-coplanar spin?

Does the magnitude of the thermal Hall conductivity depend on whether spins are coplanar or not? Also, if you have any theoretical references, it would be helpful if you could present them.
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### Heat loss of an insulated pipe vs an uninsulated pipe

So I have this exercise: A hot water pipe consists of a copper tube of length $L = 1$ m, of thermal conductivity $\lambda_{1} = 380$, has an internal radius of $R_{1} = 6\cdot10^{-3}$ m and an ...
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### Rate of Heat Flow

I was given a problem that asks me for the heat transfer power, also specifying that the heat transfer power is directly proportional to the difference in temperature. Does it refer to the rate of ...
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### Deriving the time needed until Thermal Equilibrium

Two materials of mass $m_1$ and $m_1$, specific heat capacity $C_1$ and $C_2$ and temperature $T_1 > T_2$ are separated by a conductive solid with thickness $L$, area $A$ and heat conductivity $k$ ...
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### Can an object in space have a high kinetic energy, but at the same time not release heat?

Can an object in space have a high kinetic energy, but at the same time not release heat? If the answer is no and the body has to radiate heat, why and how does it happen?
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### Sanity check: Is water a good thermal insulator?

Last week, we had a few exceptionally cold days that froze a lot of ponds and rivers. On a hike through the forest, I broke through a weak spot in the ice, and soaked my boots with ice-cold water. I ...
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### Estimating Debye and Fermi temperatures

Given the sketch of the behavior of the heat capacity against the temperature, How do I estimate the Debye and Fermi temperatures? Thank you in advance
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### Does color have an effect on thermal conductivity?

I understand the color of a surface can affect its emissivity and albedo, but that is for radiation. For conduction does; for example, painting a bowl different colors affect its absorptivity when it ...
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### Thermoelectric Seebeck Crystalline Structure

Recently reading about Crystalline Structure in metals and other forms of doping. Being that thermal energy has so called phonons could it be that crystals in metal having an effect like that for ex. ...
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### Wind velocity dependence of the temperature of a cylinder

I am currently looking for a way to model the temperature as a function of time $t$ and velocity $v$ (of the wind rushing past), of a metal cylinder that is being supplied with some heat $Q$ (a ...
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### Will the temperature reading of a thermostat change as a result of direct skin contact? [closed]

If I was to place my hand on a thermostat for an extended period of time, would this eventually result in the temperature reading rising after a period of time - or would the reading not be impacted ...
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### Why does thermal conductivity of an alloy becomes nearly flat from $0.2<x<0.8$ composition?

I am trying to understand the effect of alloying on the thermal conductivity of an crystalline alloy. I have found a great many papers where I see thermal conductivity sharply decreases from 0 to 0.2 ...
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### How long should I wait to steep my tea?

This is not a homework question, this is a real question that I have. I like to drink green tea, and I use an electric kettle which brings the water to boiling. You can purchase kettles which bring ...
Two scenarios: Solid metal cylinder of $43^\circ$ C is placed in room of $23^\circ$ C Identical solid metal cylinder of $3^\circ$ C is placed in another (identical) room of $23^\circ$ C at the ...