# Tagged Questions

Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Maybe combine with [tag:statistical-mechanics].

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### Water in pot with a heat source beneath it to boil it, does the water move?

I mean if there is there heat transfer by convection in the water? since convection requires motion. if it moves, then how can i determine the velocity of the water?
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### How to model a cooling system?

Suppose a system with a coolant, a pump, a radiator, and a constant power load object with some constant heat capacity. How can we model the dependence of the load temperature on coolant flow rate (or ...
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### Rankine Cycle Reheat Mass Flow Rate

Having worked through many examples on the rankine cycle both non-reheat and reheat, i just have one question. Can the mass flow rate of steam be calculated given only the data below? Boiler ...
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### Fuel cell HHV vs LHV

I am calculating the maximum efficiency for a fuel cell, based on both HHV and LHV. For hydrogen and oxygen in a PEMFC I calculated these at STP as 82.9% (based on HHV) and 94.5% (based on LHV). I do ...
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### Is there a temperature drop at the rotor plane of a wind turbine?

A wind turbine rotor produces power from the torque generated by the rotor blades. This torque arises from forces on blade elements which in turn are the consequence of pressure differences on each ...
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### Can we define a whole body thermodynamic model for human?

we can consider human body as a thermodynamic system and an energy exchange system, so we can investigate efficiency, entropy, exergy, is there any thermodynamic model for whole body?
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### Reversibility principle for classical mechanic

I'm studying this colloquium about quantum fluctuation relations for nonlinear thermodynamic, but I'm having a problem. Reading about the principle of micro-reversibility of the dynamic of a system i ...
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### Water heating efficiency - wood powered pool water heater

I have created a wood burning stove that has two compartments. The compartment on the bottom is to have wood inserted into it and lit aflame. The second compartment is welded directly above the ...
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### Why doesn't the heat capacity look like this?

Let us say we have a system with two states, energy $0$ and $E>0$. At absolute zero all particles are in the lowest state (of energy $0$). To rise one particle to the state $E$ this would require a ...
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### Temperature equalization by radiation between two coaxial cylinders - independent of diameters?

Ignoring end effects, assume I have a cylinder of diameter d0 at controlled temperature k0 and then introduce a smaller diameter cylinder of diameter d1 and temperature k1 to the interior. Does the ...
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### How to deduce the modified Flory-Huggins equation in this form?

In the paper of "Solution Properties of Poly(N-isopropylacrylamide)" (M. Heskins and J. E. Guillet, Journal of Macromolecular Science: Part A - Chemistry, Vol. 2, Issue 8, pages 1441-1455, 1968), they ...
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### Efficiency of a Carnot refrigerator without knowledge of the temperatures

We know that in a Carnot refrigerator we can express the efficiency as $$\eta = \dfrac{Q_1}{Q_2-Q_1}=\dfrac{T_1}{T_2-T_1},$$ where $T_1$ and $T_2$ are temperatures of the reservoirs between which ...
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### Enthalpy in MIT open courseware

I am watching Statistical Mechanics I in MIT open course ware. I have question on one of the lectures and I appreciate it if Mark or someone familiar with this topic can help me. (this is about ...
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### Pressure and temperature in Nozzle

I'm trying to calculate the change in pressure per temperature in a chamber before a nozzle throat, which will choke the flow at M = 1. I have a linear increase in temperature from 300K to 2500K. I ...
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### Phase diagram binary mixture

The Gibbs Phase Rule states: F = C - P + 2. From this it is possible to construct a phase diagram. In case of a 1-component system C=1 and where P denotes the number of phases in equilibrium. In case ...
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### Explanation of chemical potential

I made a NVT Lennard Jones Monte Carlo simulation. In this simulation I calculate the chemical potential of my system with $$\mu = \mu_{id} + \mu_{ex}$$ Where $\mu_{id}$ is the chemical potential of ...
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### Sign convention when proving the equivalence between Clausius principle and the 2nd law

I have a question about sign convention of work and heat in a proof of the equivalence between Clausius principle and the 2nd law. My lecture note brings up a model where two heat engines are combined ...
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### The driving force for first order phase transition

The driving force for the solidfication is said to be the free energy difference, but phase transition actually happens due to change of temperature toward the critical temperature. It seems that ...
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### Quanta exchange between 2 harmonic oscillators during an Otto cycle

The focus of my current studies lies on the "Quantum Otto cycle" (e.g. presented on the first pages of this paper). The "machine" as well as the "baths" are represented by harmonic oscillators. Both ...
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### Could Something Infinitely Heat Up?

If there was a perfect environment, and something was able to continue to heat up indefinitely, what would happen?.. What would be the outcome of something continuously heating up?
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### Are there any liquid that becomes solid on heating under room temperature?

The title says it all. When I searched around, there are answers which involve extra steps like super cooling and then heating or exposing the liquid to high pressure. But I would like to know if ...
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### Linear thermal expansion from statistical mechanics?

I came across a question recently regarding work done by an expanding metal and the origin of the energy used for the work, and most of the responses pointed the person to look more at the enthalpy ...
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### Microscopic Definition of Heat and Work

If I am given a statistical System, then I can define state-variables like Energy, Entropy or other Observables, and then I can (at least for equilibrium states) give the Change of Energy as: \begin{...
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### How the degrees of freedom for gas molecules affect energy

It seems a bit unclear to me how degrees of freedom help judge the amount of kinetics energy in the system. from the formula for the energy of molecule ε = u0 + (v/2)kT it can be inferred that the ...
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### Calculating heat distribution along 1D line segment?

I want to calculate temperature distribution where the heating power of $P_0$ is uniformly distributed over 1D bar TO calculate, there is heat equation.  \frac{\partial T}{\partial t}=\frac{\...
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### Energy inside a box of air with temperature variation

How to find the energy of a column of air enclosed in a box (assume adiabatic) with a temperature variation $T(z)$ in the vertical ($z$ direction) in a uniform gravitation field? I think the total ...
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### Relations between Maxwell-Boltzmann's distribution and the n-body problem velocities distribution

Solving the n-body problem numerically and finding the velocities distribution, one finds that it's quite similar to Maxwell-Boltzmann's velocity distribution. This is quite suprising because of the ...
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### Energy dissipation in spinning wheel

I was given the following question in a test. A spinning wheel A is brought in contact with an identical wheel spinning at identical speed.The wheels slow down under the action of friction.Which ...
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### Temperature of throttled flow

In a pipe with a throat, closed off to the left, I'm pouring in $\dot{n}$ atoms per second from the left. These atoms combine and do a chemical reaction, which releases energy. To the right, past the ...
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### why water can exist in both liquid and vapour state at critical point?

Water can exist in both liquid and vapour state simultaneously at 22,055 MPa and 373°c. why in these conditions water exist in both states. How can we know whether water is in liquid state or in ...
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### Justification of the State Postulate

I have just started thermodynamics (not with statistical approach but with macroscopic approach), in which the state postulate reads Only two independent intensive properties of a simple ...
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### Isothermal expansion of a cavity containing electromagnetic waves?

The cavity is perfectly reflecting , and simulates a black body . Is it that during an isothermal expansion of a cavity containing electromagnetic waves the internal energy density is constant and ...
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### what are the things that affect the ion mobility of a particular material?

what factors are important in ionic transition in a substance? please use easy word to answer as I am a high school student.
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### Computing the energy of a heat source

My son and a friend are doing a science fair project on thermoelectricity. While they understand ZT, the figure of merit conceptually, they do not know how to calculate efficiency. It's easy for ...
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### Validity of Gibbs-Dalton Law

I know that the Gibbs-Dalton law valid for an ideal gas mixture of ideal gas components. Does it also hold in the case of ideal gas mixture of real gas components? For example, could I say the ...
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### Ice and water mixed and entropy

In any introductory book, everybody has atleast done these type of questions where water at a high temp is mixed with ice and final temp and mass is asked with the understanding that zeroth law define ...
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### What could be the anharmonicity effect if phonon interact with a tilted interface?

If Phonon propagates through c-axis grown structure and at the end reach a tilted interface of GaN, what phenomena will appear there? How anharmonicity is going to effect the phonon propagation there?...
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### Why changes in the degrees of freedom implies changes in the internal energy?

In Thermodynamics we describe equilibrium states of macroscopic systems. For those equilibrium states we make a description giving one macroscopic coordinate for each measured degree of freedom (like ...
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### Increase in temperature of metal piece during filing explain by the Gibb's equation?

When we file the metal the surface of the metal gets worn out in the form of small pieces of metal. The file acts as medium to transpher the energy from the body to the metal piece in the form of work....
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### What happens when a semipermeable membrane allows only one solute to pass through?

I'm essentially a medical student where we deal a lot with osmosis. But when we are taught, it is done generally with only a single solute in consideration. What if two different solutes are used on ...
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### easier ways to cool things using electricity compared to phase changer

I can't seem to find any other ways to cool things using electricity. I understand how a phase changer works, but the whole things takes up alot of energy to cool down quite a few degrees and is ...
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### applications of second law of thermodynamics

Second law of thermodynamics applies ONLY to thermal engines? Only in cases where we have heat involved? It won't apply to a mechanical machine that works without friction, right? Also will it apply ...
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### Can the flow of hydrogen in a fuel cell be modelled as adiabatic?

Okay, so right off the bat I'll admit I need this for a problem I'm working on. Not homework though, a project, as a matter of fact. I'm considering taking compressibility effects into account, but I'...
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### Computing Maximum Heat Capacity

I've encountered a problem in my statistical mechanics class that I'm not sure I'm approaching correctly: Consider a system of N interacting spins. At low temperatures, the interactions ensure that ...
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### what are the direct real life applications of analysis of ferromagnetic materials?

I carried out Statistical analysis of ferromagnetic materials using Monte Carlo simulation, what are the contribution to knowledge based on the research work
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### Relation between Light Intensity and temperature of air

First, I switched on my bulb but not the air-conditioner. Next I switched on my air-conditioner and yet kept the bulb on. I noticed that when the air-conditioner was switched on , the same bulb's ...