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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Calculating stable orbital resonance and other factors into orbits

Firstly here is a brief summary of what I trying to accomplish. From a predetermined total solar system mass , star count in that system, per-star classification and mass I am building a system of ...
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84 views

Is thermal and electrical conductivity correlated for all phases of matter?

After reading this interesting post about why copper is a great heat conductor, I wondered if a plasma would conduct heat better than a gas. Or, are some properties like density more important for ...
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89 views

When can we assume a body to behave like a black body?

In an experiment I estimated the temperature of a Tungsten bulb filament measuring the resistance of it, and tried to verify whether the power of the filament is proportional to the fourth power of ...
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52 views

Expression of heat by the Brownian motion

folks. I was reading a paper from PRE and I'm not sure what's going on about the following equation. So for the system composed of two heat baths governed by Brownian motion, the entropy change of the ...
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41 views

Making Pudding; A complicated non-equilibrium statistical process?

There are a lot of non-equilibrium processes examples given in physics literature. But some processes that are present in everyday life are not treated. As an example, the formation of pudding can be ...
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66 views

Thermodynamics with explicit math

Nathaniel adeptly answers a question on thermodynamics by making the variable dependencies explicit: Determine the Dependence of S (Entropy) on V and T Is there a thermodynamics text that is written ...
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115 views

How does fluid velocity affect the dissolution of some solute in the fluid?

Suppose we have a perfect sphere of some solute such as sugar and we place it in a fluid such as water, at a certain temperature, that is not moving. It will dissolve and diffuse into the water due to ...
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71 views

Why can't the energy gained due to entropy be used for doing work?

Gibbs energy is defined as the energy 'available' to do work at constant temperature & pressure.The energy required to make the system from none under constant pressure is the enthalpy, that must ...
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38 views

Dependence of latent heat on pressure

It is known that the latent heat of vaporization increases as external pressure decreases. What is the cause of this phenomenon?
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96 views

Measuring variation of saturated vapour pressure with temperature

Is it possible to measure variation of saturated vapour pressure of water with time.I just hesitate about it.My suggested procedure which is incomplete is given below Procedure that I would like to ...
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33 views

Internal heating effects of a circuit element?

The heat-up of a solid circuit component in an electric circuit (for which no chemical reactions, phase changes reactions or other stuctural changes take place) may include: Joule heating $\dot Q_J$,...
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33 views

Is it impossible to find the exact analytic form of the molar volume of liquid and gas in phase transition from the van der Waal equations?

I want to find the molar volume $v_g , v_l$ of gas and liquid respectively in the coexistence curve of phase diagram with given temperature when ideal van der Waal gas $$ P = \frac{RT}{v-b}-\frac{a}{...
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20 views

Increased pressure of Liquid Pitch and Limestone (Bitumen/Asphalt) @ approximately 300 degrees Fahrenheit

If liquid pitch and limestone (20/80 mostly limestone) is pumped (appx. 5 gpm) out of a nozzle that restricts the flow compared to the flow that would be achieved straight out of the pump ( no ...
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44 views

Specific heat at constant volume

Me and my friend came across this derivation is some lecture notes of our thermal physics module. We have been trying to calculate the partial differential of the internal energy but cannot get the ...
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41 views

Thermal Equilibrium of two thin sheets

While reading Gibbs' Elementary Principles in Statistical Mechanics I came across this footnote: The most simple test of the equality of temperature of two bodies is that they remain in ...
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153 views

Temperature change in adiabatic free expansion

Consider a gas with fixed number of particles $N$ undergoing adiabatic free expansion from $V_1$ to $V_2$. Apparently we have the following relation $$\Delta T=T_2-T_1=-\int_{V_1}^{V_2}\frac{dV}{C_V}...
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Vertical wall at 3 different temperatures - do the same natural convection coefficient correlations apply?

I have an vertical enclosure that consists of 3 shelves, each with its own temperature and are thermally isolated from each other. We will call the shelves A, B, and C with A being the base shelf. The ...
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44 views

Heat transfer coefficients

I am trying to make a model of non-stationary heating on a plate and I have questions considering coefficients. I am using explicit method to solve it (have to use it). I am not sure if I am using the ...
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34 views

Is $\mathrm{d}H = C_P \mathrm{d}T$ and $\mathrm{d}U = C_V \mathrm{d}T$ always true?

Is $\mathrm{d}H = C_P \mathrm{d}T$ and $\mathrm{d}U = C_V \mathrm{d}T$ always true for ideal gases?
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56 views

How fast do I have to dry myself for a hot shower to heat my body?

I am not a physicist. I would like to know how fast do I have to dry myself after taking a hot shower to get more heat from the shower, than lost because the water on my skin increasing heat exchange ...
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53 views

Are reversible and irreversible processes frame dependent?

since it is all about time. If I have a look at an irreversible process from a frame where time runs really slow. is there a possibility of considering that process reversible from that frame?
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55 views

Thermal de Broglie wave length

If we refer to this wiki page thermal de Broglie wave length, we can see there are two expressions. One is derived using equipartition theorem, which makes perfect sense. The other one used $\pi kT$ ...
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45 views

Given the Pair Correlation Functions for a Multi-component Fluid, is There a Simple Way to Obtain the Helmholtz Free Energy?

I think it may not be possible. Given all the pair correlation functions (e.g. calculated from Ornstein Zernike theory), it seems possible to obtain the internal energy (assuming different species ...
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51 views

How water anomalies affects the Mpemba effect?

I understand basic explanation of Mpemba effect like this: Distant molecules are easier to realign into new formations. But if we compared two bottles of water like in Mpemba effect and one of them ...
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48 views

Is the system in equilibrium?

If the time derivative of the Liapunov functional related to free energy of my system is zero, can I say my system is in chemical equilibrium?
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59 views

Necessity of infinitesimal steps for reversible processes

Is there a mathematical proof for why a reversible process is one that has many infinitesimal equilibrium steps, rather than fewer large steps? Maybe something along the lines of this?: \begin{...
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24 views

Can a gas be modelled as a low density blackbody, if we want to consider how detectable it will be in space?

The answer to this question taught me about the sort of parameters I need to consider if I want to consider how "detectable" an object in space is. I want to consider the detectability of a ...
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49 views

Heat loss from hot cast iron oven

I am considering an unconventional pizza oven made from cast iron. What is a good formula for estimating non-radiative heat loss from a 450C/850F surface in a 20C outdoor environment? I am looking ...
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38 views

Question about fluid expansion

Hy, When a hot and dense fluid suddenly expands, how much can it cool down. Lets take for example an expansion valve from an AC, does the fluid do work when passing through the valve or does it not ...
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271 views

What is the minimum temperature of a metal surface to ignite a cigarette touching it perpendicularly?

Suppose you have a cigarette tip touching a metal surface at a 90 degree angle, exposed to air at 25C / 1atm, no wind, normal oxygen concentration. Cigarette is a regular brand, tobacco with paper ...
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104 views

Negative temperature thermodynamics

I asked this question about thermodynamics. I considered $$T=\frac{\partial U}{\partial S}$$ at constant $V$ and $N$ (number of particles), but now I can't figure out the change of $U$ with respect ...
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86 views

Calculation of Water Temperature

In a close looped process the soft water (approx. $200\frac{m^3}{h}$ at $14$ barg) gets heated gradually from the ambient temperature to $\Delta$T of 20°C in $13-14$ minutes, i.e. if amb. temp is 45°C ...
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114 views

Lindblad equation derivation

I'm reading A simple derivation of the Lindblad equation. It introduces a Hamiltonian for a system consisting of a principal system $S$, a heat bath $B$ and an interaction term: $\hat{H}=\hat{H}_S+\...
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72 views

Simple thermodynamic proof that light from a source cannot be focused to heat an object above the source's temperature

I was thinking about the question in the title. I found the following thread, and some of the answers are making my head spin! Is it possible to focus the radiation from a black body to make ...
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84 views

LOCAL Temperature Gradient and Stress

I'm investigating the thermo-migration failure mechanism in nanoscale ICs interconnects. Typically, a nano wire under thermal stress suffers from material/mass migration or void nucleation if it ...
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227 views

Why is Cv greater than Cp during anomolous expansion of water?

Well, in general $c_p> c_v$ for most cases but for water having anomolous expansion from $0^{\circ}\mathrm{C}$ to $4^{\circ}\mathrm{C}$ the order is just opposite, $c_v >c_p$, why?
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245 views

Why doesn't the 1 dimensional ising model have a transition temperature?

Consider a 1 dimensional chain of spins that are able to either have the value $\sigma =$ $+1$, $-1$, from now on referred to as up and down. For the Hamiltonian $H = J \sum_{i,j} \sigma_i \sigma_j$ ...
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Does degeneracy affect the adiabatic relation?

The adiabatic relation is $P=K\rho^\gamma$. For ideal monotomic gas $\gamma$ is 5/3. For nonrelativistic degenerate electron(inside white dwarf), $\gamma$ is also 5/3. Is this just an coincidence? ...
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92 views

Interpretation of partition function and thermodynamic potential

So in the microcanonical ensemble the partition function $\Omega$ counts the number of microstates for a given $(NVE)$ configuaration and $S = k_B \ln (\Omega)$ is the entropy. The most likely state ...
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43 views

Entropy of this system

We have a system with two energy states $E_0$< $E_1=0$. We also know that state $E_0$ can only take at most $m$ particles. Curently, there are $n<m$ particles in $E_0$. Now, I am supposed to ...
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313 views

gibbs free energy and maximum work

I'm getting confused between two important results.... Gibbs free energy G = H-TS where h is the enthalpy and S is the entropy. This relation indicates only when the temperature and pressure are ...
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673 views

Isentropic and Isothermal Compressibility

Why isentropic compressibility is greater than isothermal compressibility ? While deriving $C_p$ and $C_v$ relation, I got $\frac{Cp}{Cv}$ as $\frac{ke}{Kt}$. Which tells us that $Ke > Kt$. But ...
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168 views

fugacity of gases and gaseous mixtures

Is fugacity defined only for gases and gaseous solution.? In many books it is given that fugacity is "effective pressure", what does it mean? If it is applicable to liquids and liquid solutions then ...
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306 views

How much energy does a powerlifter need to perform a session of squats?

So I started the math myself and I'm hoping someone can look this over and improve on my idea. Let's say that a powerlifter performs the following sets of squats: % 1RM = lifted weight in percent ...
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99 views

Are Maxwell Relations valid only out of saturation?

My thermodynamics book suggests that the Maxwell Relations must be used when dealing with a single-phase system. The equations come right after the section Mathematical Relations for the Homogeneous ...
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143 views

What are the thermal properties of a “perfectly rigid” container?

can a "perfectly rigid" container be a diathermal boundary? I checked the wikipedia article for heat and read: Kinetic theory explains transfers of energy as heat as macroscopic manifestations of ...
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102 views

White bread toasted seems hotter than brown bread?

Ok this is a bit of a random question but I 99% of the time use white bread for toast and I always toast my bread the same amount and every time I take it out it's too hot to handle and the butter ...
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282 views

What algorithms can be used to compute the binodal in a ternary Flory-Huggins theory?

What are the most popular algorithms used to obtain a binodal curve for the ternary mixture (starting from Flory-Huggins theory)? I would like to obtain a plot similar to the one calculated here http:...
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86 views

Free energy a continuous function of temperature but may not be differentiable everywhere?

So according to my understanding, the free energy of the system should be a continuous function of temperature. This is because if the free energy is not continuous at temperature T, then at this ...
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196 views

Effusion of particles from one box to another - pressure calculation

Suppose we have a container divided into equal halves. Right half is fixed at temperature $T$, volume $\frac{V}{2}$. Initially it has pressure $P_0$, a hole of area $A$ is opened between them. I ...