Questions tagged [thermal-conduction]

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Why does capillary in gas thermometer have a temperature and pressure gradient?

I have been learning thermodynamics using Heat and Thermodynamics by Zemansky, in which he mentions The gas in the capillary connecting the bulb with the manometer has a temperature gradient, that is,...
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Does the isotropy definition of a perfect fluid imply no heat conduction?

Weinberg defines a perfect fluid (Chapter 2, Section 10) as one where each fluid element appears isotropic in a reference frame moving with that element. From the definition of the stress-energy ...
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Does Pipe Temperature Directly Correlate To Water Temperature? [closed]

I need to know if just by taking a boiler flow pipe temperature that will tell me the water temperature that is flowing through the pipe. For example if the water from the boiler travelling through ...
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Entropy change of an isolated system consisting of two thermally conductive blocks of equal isochoric heat capacity at different temperatures

A classic example considered in most introductory treatments of elementary thermodynamics consists of two thermally conductive (e.g., metal) blocks placed in thermal contact. In particular, I find ...
369 views

Should I hold a baby formula bottle to cool it down faster?

This is an interesting and somewhat surprising physics problem - holding a hot object in your hand will cool it down faster, even if the air around is colder. I guess that 90% of people would be ...
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Estimating Heat transfering by measuring [closed]

Consider the setup with closed chamber with two flat metal objects with know dimensions. The first object can be heated or cooled by peltier module and the second one is placed on top of the first one....
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Definition of convection heat transfer not unambiguous? [duplicate]

What is actually the definition of convection in the context of heat transfer, if there is one? Wikipedia states: Convection (or convective heat transfer) is the transfer of heat from one place to ...
1 vote
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Heat equation two stage process - Additivity? some other approach?

I'm struggling a bit how to apply a standard solution to the heat equation to my own practical problem. I have some intuition, but do not know whether this intuition is justified. I don't understand ...
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Why clothes keep us warm?

I want to understand why clothes keep us warm. I understand that they reflect back thermal radiation and also trap air thus significantly reducing cooling due to thermal convection. My question is, do ...
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Heat exchange speed of two liquids separately vs their mixture

I'm quite oblivious about basic high school physics, so pardon my misuse of terms and inability to google the answer. I want to solve a puzzle that I face in my daily routine. Suppose I want to make a ...
1 vote
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Why are absorbing bodies hotter over time than reflecting bodies?

I recently learnt about energy transfer by EM Waves and came across the formula for momentum transfer, i.e. Δp = U/c → perfect absorption Δp = 2U/c → perfect reflection then why do absorbing bodies ...
32 views

Temperature of plasma sputtering magnetron

This question is in regards to DC magnetron sputtering for coating surfaces. My main goal is to determine how much heat will be seen by the anode, cathode and the target. As well as to determine what ...
39 views

Thermal resistance in heat transfer

Can a material experiencing heat generation be represented by thermal resistance and  included in a circuit analysis? If so, why? If not, why not? Consider a case with the solid cylinder with the heat ...
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Rate of heat flow through rod of variable conductivity

Incase wher we have an object( a rod ) with its conductivity not uniform say varying with temprature. Then will heat flow through it at same rate from every cross section of the object?
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Glass having huge thermal mass when stirring drinks

In the book "Liquid Intellegence: The Art and Sience of the Perfect Cocktail", David Arnold says this: My question is how the glass affects the chilling? What does he mean by the glass ...
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Lumped body analysis

$k$ - thermal conductivity, $h$ - heat transfer coefficient, $\rho C_p$ - Volumetric heat capacity, $T$ - temperature $T_\infty$ - Temperature of exposed cooling surrounding environment Consider two ...
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At what circumstances is Nusselt's theory of evaporating falling films valid?

Nusselt's theory of evaporating falling films assumes no convection and neglects the effect of inertia. At what circumstances is that valid? Any books or articles that discuss this in depth would be ...
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Approximating the temperature of the wall of the heating jack of a reactor

Suppose we have a reactor containing some fluid that we heat through a heating jacket containing some other fluid. I am interested in approximating the temperature of the wall of heating jacket. I ...
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Why slow compression with conducting walls should be isothermal?

I know that for an isothermal process heat transfer is necessary so process should be slow and walls should be conducting for heat transfer to occur as a process cannot be isothermal and adiabatic at ...
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Conduction in liquid and gas

Is this condition correct, "if liquid and gas heated from top, then it will be possible for 'conduction' to occur" ? One reason i can think is : when liquid or gas is heated from sideways or ...
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How do I calculate the rate of heat loss from an enclosure when I have a plot of temperature vs time and the enclosure's material details? [closed]

I have an enclosure running an ON/ OFF temperature control system. The below graph shows internal air temperature over time. I have the raw data providing actual values. I have the dimensions of the ...
46 views

Heat transfer vs. Volume transfer [closed]

Apologies in advance if this has been addressed before... it's something if a daily puzzle during my morning ablutions and I haven't gotten a handle on it yet. Consider the hot water pipe from my ...
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Anisotropic heat flux from anisotropic shape

Expanding the discussion in Thermal conductivity from the mass distribution of an object Is it possible to have asymmetric heat flow with linear materials with temperature independent thermal ...
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How much longer to thaw an elephant than a chicken? [closed]

Twenty-five years ago I came across this question on a physics olympics exam and I've never really worked out a satisfactory answer... How much longer does it take to thaw an elephant than a chicken? ...
177 views

Heat diffusion equation in terms of entropy?

Ok, I am very rusty in thermodynamics. In fluid mechanics books, you can find the heat transport equation in terms of temperature $T$:  \rho c_p\left(\frac{\partial T}{\partial t}+\boldsymbol{u}\...
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Fourier Heat conduction law and two insulated layers heat conduction rate [closed]

If we apply Fourier heat conduction law to a system of two insulated layers joined together, of the same area, can we always assume that the rate of heat transfer between the layers will eventually ...
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Difference of the Transmission Coefficient between Thermal and Charge Conductance by Nonequilibirum Green Function Method

The equation 57 in the reference [Jian-Sheng Wang, Jian Wang and J. T. Lu, Quantum thermal transport in nanostructures, Eur. Phys. J. B 62, 381 (2008)] explains the the transmission coefficient for ...
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Thermal conductivity from the mass distribution of an object

Thermal conductivity is a property normally related to material. But it is also possible to relate it to objects. Consider two objects of different shapes made by the same homogeneous material. How ...
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Modelling of a heat exchanger [closed]

re mathematician so im so lost... Any help will be very appreciated!
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Do linear expansion, area expansion, cubical expansion all occur simultaneously in a metal rod when heated?

Consider a metal rod being heated. As metal rod is a good conductor, it spreads heat all through it. If so I think all the linear,area and cubical expansion takes place simultaneously practically. Am ...
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What's the percentage/relationship of evaporative cooling applied to the liquid by an evaporating/expanding gas?

The example below is simply to provide illustration of the problem. This isn't a homework question. I'm trying to visualize the relationship between liquid and gas at the boundary and I'd appreciate ...