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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How to have a power plant that works with a 3stage turbine but with just one stage of reheating

There is a power plant that has a 3-stage turbine (hi-press,medium-press,low-press) but with just one reheat stage. The cycle is thermal,so the working fluid gets QH from boiler,goes to turbine ...
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34 views

What is the use of thermal boundary layer and velocity boundary layer?

In heat transfer by convection, why must we show the thermal boundary layer and the velocity boundary layer. What do they signify? Also how are these terms related to the Prandtl number? And what is ...
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22 views

Separating Interaction of Heat from Electricity?

I have a rod where electricity of frequencies 1-360 Hz is passed through. It is affected by heat. I am evaluating the energy involved in such a process, contributed by electricity and heat. The ...
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42 views

Gravitational waves parallel

Just an idea to illustrate the gravitational waves. This kind of analogy is proposed: When you have a rotational motion of the fluid, some small amount of the energy is radiated as a pressure ...
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10 views

How to express Darcy velocity as a function of mobility and capillary pressure?

I have a problem with deriving a certain expression for the Darcy velocity of water, when we have a piston like displacement of oil with water. The expression I am supposed to show is the following: ...
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33 views

car dashboard problem

I stumbled upon this question while I was driving my car. On my dashboard I have fuel gauge and engine temperature gauge next to each other, look at the pic: http://i.stack.imgur.com/aDgKj.png Fuel ...
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17 views

What's the simplest, first order way to calculate the temperature change in this scenario?

I am trying to model this experiment in a simple (i.e., relatively analytic, non-computational) way. I have a little square of a thin film (10s of nanometers thin) of material A, on a relatively ...
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23 views

Hagedorn temperature as a control parameter of saddle - node bifurcation

Can we interpret the Hagedorn temperature as a control bifurcation of equilibrium parameter of the saddle - node type?
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18 views

What is temperature dependence (Schottky defects)?

The problem requires us to use the following property to determine the temperature dependence: For a system in thermal equilibrium in a heat bath at temperature $T$ the Helmholtz free energy is a ...
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35 views

Mechanical equivalent of heat => transfer from work W to heat Q

Consider the following experiment to determine the mechanical equivalent of heat $\mu = \frac{\Delta W}{\Delta Q}$ Not seen in the picture is a weight with known mass hanging down the cord. When you ...
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34 views

Obtain an exact expression for the heat capacity of the system

Before anyone mentions it, yes I did my research and found this question on this site. My question is his exact question, but I'd like some clarification or maybe a bit more explanation than the one ...
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21 views

Understanding the concept of temperature vs. mean energy/heat capacity of a system

I need help understanding a concept in thermodynamics. What is the relationship between temperature and mean energy? What is the relationship between temperature and heat capacity? What I know: ...
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31 views

what is the relation between heat capacity and mixing ratio

I am supposed to derive an expression for the specific heat capacity $c_p$ for air with a water vapour mass mixing ratio of $\mu$. The hint is: (Use the fact that $c_p= (\frac{\partial H}{\partial ...
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17 views

Can I find equation of state if I have a type of potential?

How can I find equation of state if I have a type of potential? For example, if I want to take into account ion-ion, ion-electron, electron-electron interaction in white dwarfs.
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47 views

Thermodynamics questions

does a refrigerator full of food consume more power if the room temperature is 20 degree Celsius than when it is 15 degree Celsius? or is the power consumption the same?
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36 views

Name of the fourth entropy potential

Wikipedia's "Free Entropy" page lists three entropy potentials: Entropy, $S$, with natural variables $U$ and $V$ Massieu Potential / Helmholtz Free Entropy, $\Phi$, with natural variables $1/T$ and ...
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52 views

Please help me with this doubt from thermodynamics

My textbook says that net rate of heat transfer due to radiation is $\epsilon \sigma A(T^4-T_o^4)$ but i couldn't understand it. Rate of emission is $\epsilon \sigma A T^4$ and rate of absorption is ...
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20 views

Computing temperature given heat source

I am new to thermodynamics, and is trapped on a very simple problem. In solving the heat equation, I need to compute the heat source given temperature. Given the temperature at the heat source (a ...
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39 views

Why is thermal energy not a state variable?

It is written on Wikipedia: (https://en.wikipedia.org/wiki/Thermal_energy) The thermal energy of a system scales with its size and is therefore an extensive property. It is not a state function of ...
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23 views

Rate of Convection

Today in Geophysics the professor briefly introduced the mantle convection processes how it rises and drops. He also said this generates Earths magnetic field and we know that Earth Magnetic field ...
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25 views

Work + heat absorbed in a thermodynamic process

The question describes a simple isobaric closed cycle. The temperature is on the y-axis and volume on the other. There are 4 states. The question asks: ''Find the work done on the gas in the cycle and ...
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36 views

On Rayleigh-Jeans black body distribution derivation

When trying to derive the Rayleigh-Jeans distribution function, all authors say that in k-space each solution of the electromagnetic wave functions(of waves inside a cubic black body) represents an ...
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13 views

why it is said that the mach number of noble gases should be less than 0.1 in order to avoid non linear effects?

while reading about the construction of thermoacoustic refrigeration i read that the mach number of the noble gases should be less than 0.1 to avoid non linear effects. what is the science behind ...
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46 views

Why do expanding gases lower temperatures around them?

I want to give you an example to my question: When you spray some pressured gas on a surface, liquid water for example, the surface could freeze. but why.. As far as I know molecules close to each ...
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29 views

How much pressure is need to lift tiles against gravity?

Vitrified tiles of size 600 mm by 600 mm and weighing about 7.5 kg each were laid with cement on floor of a building about a year ago. Building has glasses all around and premises are not occupied. I ...
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42 views

Heat Losses to furnaces

I am looking in to the thermal efficiency of a furnace vessel. I am wanting to get a full, or at least better, understanding on the calculations needed to look at the thermal efficiency. So I know ...
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24 views

Material preventing nucleation, why is it not used for soda container?

I would like to know the answer to the question "why do materials preventing heterogeneous nucleation of $CO_2$ aren't used for soda bottles and glasses?". Two possible answers so far that I thought ...
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31 views

How heat can be transferred away to cool down objects

Based on the 4 ways to transfer heat which is vaporazation, contact, radiation, and convection. If I needed to cool down an object for example a hot soup how would I do it, put it in the freezer to ...
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43 views

What kind of conservation law is energy conservation in thermodynamics?

As I understand it, Noether's theorem is an important result that allows us to show when certain kinds of conservations arise. Is energy conservation in thermodynamics a result of Noether's theorem? ...
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36 views

Thermodynamic derivation of condition for equilibrium of triple line

Edit:(4/1/2016) Okay, I get how the required equation arises from force balance. All forces are acting on the same length, so the length cancels out of the equation and what we've got is essentially ...
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23 views

Double check my understanding of the eventual state of the universe according to current theory

According to current orthodox physics theory, no energy is being created and put into the universe, and the universe's energy is finite. As stars like our sun expel energy in every direction, then we ...
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23 views

Existence of statistical ensemble with fixed energy but varying volume

To me, every statistical ensemble in statistical physics was introduced beginning with the microcanonical ensemble, in which every microstate is equally probable. A canonical ensemble is described by ...
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63 views

Dissipative forces and reversible processes

A book that I have contains the following lines: For a process to be reversible, the dissipative forces such as viscosity and friction should be absent. My question is why?
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59 views

What will a glass look like in 500 years?

The glass is in a metastable state. It is changing constantly. So what will a piece of glass look like in 500 years in room temperature?
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27 views

In stochastic thermodynamics, can you define the notion of equilibrium for microstates/individual trajectories?

Recently there has been quite some research on interpreting statistical thermodynamical quantities at the level of microstates/individual trajectories. Although I did not find any ...
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23 views

Specific heat capacity for Adiabatic process

We can define infinite number of specific heat capacities between two temperatures(e.g $c_p ,c_v$) . Could we do that for an adiabatic process. As for adiabatic process heat addition or removal is ...
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60 views

Why isn't Hydrogen used as fuel in Internal combustion engine?

I was looking at hydrogen cars and found out that hydrogen is mainly used in hydrogen cells to produce electricity instead of combusting it like gasoline in a cylinder to produce heat energy. Why ...
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69 views

Deriving the Thermodynamic Beta

Pardon me if this question has been asked before. I'm an undergraduate student studying chemistry at the moment (specifically towards synthetic chemistry). Recently I've been trying to study ...
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11 views

Diffusion coefficent for a mixtures gases?

In the Pauli Lectures on physics volume 3 it is stated that for gas mixtures the diffusion coefficient is given by: $$D=a'' \frac{1}{n} (n_1 \bar u_1 l_1 + n_2 \bar u_2 l_2)$$ Where $n=n_1+n_2$. How ...
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39 views

Can I regard Maxwell construction as a patch to van der Waals equation?

There is an unstable zone in the P-V plot of van der Waals equation where if you compress the gas the gas expands. The unstable zone is physically unacceptable so we use Maxwell construction to ...
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31 views

What creates multiplicity in counting the number of ways energy quanta can be distributed among a collection of atoms?

Say that I have $q$ energy quanta, which I intend to distribute among $N$ indistinguishable atoms in some collection. These atoms have no limit on the amount of quanta they can contain. Am I right ...
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45 views

Expansion in bimetallic strip

Suppose there is a bimetallic strip with thickness 't' .The coefficient of linear expansion on heating the metals are alpha 1 and alpha 2.Now if the bimetallic strip is subjected to a temperature ...
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40 views

Thermodynamic reversibility, Landauer's principle, and Maxwell's demon

A lot of the literature surrounding Landauer's principle (and relating it to Maxwell's demon) talks about whether or not a logically irreversible process can be thermodynamically reversible. But why ...
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38 views

Cyclic model of the universe and second law of thermodynamics

Cyclic model from wikipedia The above link shows some theories on cyclic model. It states that a scientist named Richard C. Tolman showed that the cyclic model proposed by Einstein can not be ...
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38 views

Thermal conductivity of a binary gas mixture

I want to estimate the thermal conductivity of binary gas mixture, say water vapor+nitrogen. I assume the mixture as ideal gas. The molar fraction and thermal conductivities of the components are ...
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30 views

Difference Value of the Specific heats at constant Pressure and Temperature of Real Gases

As in ideal gases, we can have the equation of $C_p=C_v+R$, or to be precise, the difference of the Specific heats of ideal gases at constant pressure and volume is the universal gas constant. But, we ...
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45 views

Chemical Thermodynamics - Maxwell Relations

I am trying to derive an expression for the isentropic compressibility in terms of thermal expansion coefficient $\alpha_P$, the isothermal compressibility $\kappa_T$ and the constant pressure heat ...
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32 views

When can we just look at just the partial derivative of energy?

I am reading a text about fluid mechanics and in the chapter about the (zero viscosity) Wuler equation this showed up: We consider now the kinetic energy and the internal energy of the system and ...
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75 views

Carnot cycle's paradox

Carnot cycle is a reversible cycle. By definition a reversible cycle must have an infinitesimal temperature difference. That means ($T_{high}-T_{low}$) is very very small. Any finite temperature ...
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93 views

Time between two collisions in a 2D gas

I'm trying to code a simulation of a 2D gas in a box. The molecules are represented by circles of radius $R$ having elastic collisions with the walls only (for now). I read that the average time step ...