# Tagged Questions

Heat is energy transferred from one system to another by thermal interaction. In contrast to work, heat is always accompanied by a transfer of entropy. Heat flow is characteristic of macroscopic objects and systems, but its origin and properties can be understood in terms of their microscopic ...

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### How do you determine the heat transfer from a P-V diagram?

I doubt this question has been addressed properly before, but if there are similar answers, do direct them to me. I am currently studying the First Law of Thermodynamics, which includes the p-V ...
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### LED Thermal Modeling (How to solve heat equation with constant heat source)

I have a mechanical design with LEDs that generate heat. I want to estimate the temperature at the LED junction vs. time, but especially at steady state. Knowing the LED voltage drop and current, I ...
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### How can I understand a Vortex Tube and its efficiency?

A Vortex Tube takes a pressurized input stream, most typically of a gas, and creates two output streams with a temperature differential. Apparently, it has been described as a Maxwell's Demon. Both ...
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### Optical element is heated by laser: is it possible to get oscillating heat distribution?

Imagine that we have thin optical element, which is irradiated by laser. Laser heats element, so there is some heat distribution in element. There is a heat sink through upper and lower element faces ...
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### Could we really charge metal plates using microwaves?

While skimming through Dielectric heating, I read that they use microwaves to charge the plates. How do they do that?
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### Finding electric power generated using heat transfer

I'm working through an example I have been given to study. Suppose I have a 2m X 4m photovoltaic panel on my roof that is irradiated with a solar flux of $G_s = 700W/m^2$. Given: $\alpha_s = 0.83$ ...
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### Calculating the coefficient of thermal expansion in liquid

I am trying to write a matlab function that calculates the coefficient of thermal expansion of water from a given temperature. From what I understand the thermal expansion coefficient is calculated as ...
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### Time constant of ice melt

I'm familiar with problems of "how much ice can you melt given some amount of energy", but I'm writing to get some clarification on the time constant of this event. This question might be somewhat ...
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### Indicators on how even the heat is distributed?

I'm wondering if there are any good indicators on how even the heat is distributed on an object (for simplicity, a flat object maybe)? What are the possibly reasonable ways to maximize the evenness if ...
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### Is the heat required to alter the Higgs field an 'absolute heat'?

I have read and heard that manipulating the Higgs field would require heating up a local geometry to ridiculous temperature. I am trying to understand if there are stars or places in the universe ...
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### What is the difference of work $W$ and thermal energy $Q$ in thermodynamic Stirling-process for ideal gas?

What is the difference of work $W$ and thermal energy $Q$ in thermodynamic Stirling-process (in simple form) for ideal gas? I think that you need work to preserve this process and you bring thermal ...
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### The effects of heat on gravitational fields

In boiling soapy water, globs of soap coalesce as the temperature increases to boiling. Does this mean that temperature increases the gravitational pull of bodies?
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### Sensible heat question (solving for temperature)

If $55 034.175 \rm{kJ }$ of heat are transferred to $150 \rm{kg}$ of ice at a temperature of $-12.15 ^\circ \rm{C}$, calculate the temperature of the resulting water. Using $Q = mc(t_2-t_1)$ or ...
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### Why do phonons cause excellent heat conduction in diamonds?

Phonons are the quantum of lattice vibrations in crystals and are not to be confused with photons, the gauge bosons of the electromagnetic force. Apparently, they contribute to heat conduction, but I ...
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### For how long can we make an air balloon stay flying via remotely controlled heat system?

I wonder how a function $$f=f(h, m_{\mathrm empty}, V_{max}, T_{h}),$$ with the top height $h$, the empty mass $m$, the maximum volume $V_{max}$, and the temperature of the heater $T_{h}$ would look ...
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### Mechanical Equivalent of Heat

Recently I have been looking up James Joule's experiment regarding the mechanical equivalent of heat. After viewing some drawings of the apparatus, I assumed that the lines holding the weights would ...
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### Thermodynamic relations from Gibbs-Duhem

Given the Gibbs-Duhem relation $V dp = S dT - N d \mu$, I am having trouble deriving the following identity: $\ (\frac{\partial N}{\partial \mu})_{V,T} = N (\frac{\partial \rho}{\partial p})_T$ ...
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### Constant volume specific heat

A monatomic ideal gas is confined to move in two dimensions. What is the constant volume specific heat for this gas? Consider a system of N independent harmonic oscillators moving in two dimensions. ...
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### How is pool boiling dealt with by today's process design methods?

Designing evaporators and industrial reboilers often requires at initial stages of dimensioning (i.e. when the support from a finite element software tool to model the system of interest, isn't yet ...
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### What is the insulative value of water?

I am having a hard to finding what the R value of water is. I am trying to compare it to styrofoam (which has an R-Value of 5). EDIT Based on the assumption that water has an insulative property, ...
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### MIT's 230% efficient LEDs. A reprise about cooling

This is a reprise of the question Can someone explain the science behind MIT's 230% efficient LEDs? The PRL paper doesn't detail what the efficiency of heat-to-light energy conversion is, which in ...