# Tag Info

### How to calculate internal convection loss in a sealed container?

This is a problem of free or natural convection in a cavity. The general idea is to find the Nusselt number, from which you can get the convective heat transfer co-efficient, and from there calculate ...
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### Can people feel the low heat radiation from very cold surfaces?

Will the wall feel like it's radiating cold on the person? Nothing "radiates cold". Everything radiates some amount of infra-red radiation and hotter things radiate more IR. If you are ...
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Accepted

### Can people feel the low heat radiation from very cold surfaces?

Regarding feeling the coldness: Sure, humans feel when their skin emits more IR radiation that is received. You can test this easily by opening a freezer and standing some ways away from it (avoiding ...
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### Can people feel the low heat radiation from very cold surfaces?

While I have not done the numbers for your very particular follow up question (nevermind that it's impossible to reach 0K), I have every reason to believe the person will survive. Consider the night ...
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### Can people feel the low heat radiation from very cold surfaces?

Yes they will feel the coldness, but it's the lack of heat radiation, not radiating coldness. Essentially, the scientist's body is radiating more heat than it is receiving, and it is this difference ...
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1 vote
Accepted

### Thermal radiation in hollow sphere

I think the easiest way to look at this is to imagine a vacuum in the cavity. Heat radiated from one side of the inner surface, is almost immediately reabsorbed on the opposite side of the cavity, so ...
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### Thermal radiation in hollow sphere

As far as I know,we only account for the outer surface (surface area of the sphere).There are two kinds of heats transfer going on here: 1)**Radiation:**Body emits and absorbs heat to and from the ...

### 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?

I wouldn't bother with the peak to trough time. You know the heater rating is 18 Watts (which is energy in Joules per second) and this maintains a more or less constant temperature. Visually the ...
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### Heat transfer vs. Volume transfer

Imagine running the water at a very low flow rate, so low that the heated water reaches ambient temperature by the time it comes out of the tap. In this scenario, water coming out of the tap will ...
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### Heat diffusion equation in terms of entropy?

If you divide your 2nd equation by T, you get $$\rho\frac{DS}{Dt}=\frac{1}{T}\nabla \centerdot\left(k\nabla{T}\right)=\nabla \centerdot\left(\frac{k\nabla{T}}{T}\right)+\frac{k(\nabla{T})^2}{T^2}$$ ...
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1 vote

### Heat diffusion equation in terms of entropy?

Differentials. Once you know the relation $d a = f(\mathbf{z}) db$, where $f(\mathbf{z})$ is a known function, you can replace every differential operator acting $a$ with the corresponding ...
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1 vote
Accepted

### Fourier Heat conduction law and two insulated layers heat conduction rate

In a steady state condition, when the internal energy of each layer keeps a constant value, the same amount of heat "crosses" the two layers. Remark. This conclusion holds even without ...
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