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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Modeling an Adiabatic Expansion (EES)

How would one model an isentropic (reversible) adiabatic expansion using thermodynamic software in order to determine isentropic work? What I am looking for is an actual pressure-volume curve for the ...
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143 views

Difference between Residual Function and Excess Property

Sengers describes the deviation function as the difference of the actual mixture property and as determined from a model. If this model happens to be the ideal gas model, then it is also called ...
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Distribution of temperature in a plume of a jet

The exaust gases of a plume of a missile have a distribution in temperature and in density vs. distance from the nozzle. Using a CFD software it is quite simple to get such distribution. Is there some ...
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I need to calculate the temperature of some flat copper wire as it loses contact with a chilled capstan roller

I need some help in designing a system for cooling wire as it comes off a resistance annealer. I need to calculate the temperature of that flat copper wire as it comes off a chilled roller (call it a ...
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50 views

Thermal Conduction through sphere

In general, a sphere with conductivity $\kappa$, heat capacity per unit volume $C$ and radius $R$ obeys the differential equation at time t: $$C\frac{\partial T}{\partial t} = \kappa \frac{\partial^2 ...
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How to calculate net power output of heated, expanding air?

I'm interested in designing and building a Stirling engine which uses air that has been heated, which expands and then acts upon a piston producing power. There is a fixed amount of air inside the ...
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38 views

Hamiltonian (temperature?) and frame of reference

So we can define a particle by defining its kinetic and potential energy, knowing that we can get a wavefunction describing a particle. But the kinetic energy involves motion, and motion can be ...
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29 views

If maximal work is extracted, in what manner does the heat flow between bodies?

There are two bodies starting with different temperatures and specific heat capacities (for simplicity assume that the bodies are solid to the volumes are constant). Let the rate of heat flow from ...
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39 views

Which metal will be on the surface after solidification?

I know that there are some metals that just "like" to be on a surface, so if I make an alloy of such metal and some other metal, the first one will be on the surface after solidification of initially ...
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How to calculate the amount of energy in joules/s that gas oven uses?

I know there may be missing information, but my question is really simple and yet I haven't found an answer to it. To make things easy, let's assume we have a $40×40×40$ cm oven that we want to keep ...
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Understanding how clouds form: warm air near the earth's surface?

I'm trying to understand how clouds are formed. I've read that it begins with air near the earth's surface heating up. But I'm hearing two different reasons for how this happens: Air pressure near ...
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Does transverse flow always assist in mixed convection?

I am dealing with both natural convection and transverse forced convection over a flat plate. There are 4 different situations: Upward-facing cold plate Downward facing cold plate Upward facing hot ...
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Landau free energy

I am reading the statistical mechanics by Pathria in Chap 12. I have a question about the Landau free energy. What is the physical reasoning for that the free energy could be a functional of the order ...
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68 views

Cooling power for cloud chamber

I'd like to build a small Peltier cell cooled cloud chamber. The cold surface would be a copper sheet with a surface of 200x200 millimeters. Is there a way to even guess the cooling power needed to ...
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18 views

Is there a way to tell the rate of temperature change due to provided energy?

Let's say we have an isolated system containing two bodies with different temperatures. The bodies are touching each other. Is there a way to tell how long will it take them to reach thermodynamic ...
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53 views

Proving $RTln(a_i)$ equal to non PV work done by system,where $a_i$ is activity

First of all many here will might say that it is Chemistry question.If you think so then read this article and then answer question. Question is --- We know chemical potential is defined as $\mu_i ...
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Natural refrigeration

I have an electricity-free pot-in-pot refrigerator that uses evaporative cooling to keep the inside cool. However, I live in a very humid place, so the rate of evaporation will be low and hence this ...
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32 views

Question regarding temperature as a property of a system

This is probably silly question but I got stuck while reading “Lectures on Theoretical Physics-Thermodynamics and Statistical Mechanics” by Sommerfeld. In the first chapter it says : Temperature ...
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59 views

Thermodynamics First Law Question - Expansions

Two thermally iso- lated cylinders, A and B, of equal volume, both equipped with pistons, are connected by a valve. Initially A has its piston fully withdrawn and contains a monatomic gas at ...
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62 views

Adiabatic Expansion with expanding control volume

I have a tube with a length $L$ and diameter $d$ that is open on 1 side. At a certain point (say $x$) from the closed end of the tube, I have a gas with a high pressure. At this point, $x$, there is ...
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91 views

Physical meaning of isobaric line in T-v diagram

Hi, I was just reviewing some slides from my thermodynamics class, and in one of the slides the professor asks what is the "physical meaning of the slopes" of the isobaric line in a T-v diagram. ...
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34 views

Explain Heat Transfer

I would like to know what are these formulas used for. There is no intro about it in my book at all, and I am reading Heat Transfer book. If needed Q. can be edited.
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149 views

Determine pipe outlet temperature without length?

Let's say I am flowing a fluid through a pipe that has a constant surface temperature. Is it possible to determine the heat flux on the inner surface without knowing the pipe's length when the only ...
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Applied / environmental question: direction of exhaust fumes

I'm not sure the Physics StackExchange is the perfect place for this environmental/applied physics question, but as I found no forum more fitting I ask my question here. Otherwise please move my ...
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How hot is it on the slopes of an erupting volcano?

I was watching The Return of the King and just after Frodo and Sam destroy the One Ring, they run out of the mountain and hide on top of a rock as the volcano erupts and lava flows past them. Is this ...
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where i can find thermodynamics properties of octane

where can I find thermodynamics properties for octane at $T_s$? I need this properties or where can i find all ? $$liquid-density=\rho_l=?$$ $$vapor-density=\rho_v=?$$ ...
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Building a magnetron powered steamer

I am wanting to build a microwave powered steamer for a reverse engineering project in university. I've read up some on this and know that its not as efficient as a heating element. I'm curious about ...
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90 views

Questions about the second law of thermodynamics

I can not understand the second law of thermodynamics and have trouble explaining the following questions: 1) In the tropics the water near the ocean surface is warmer than the deep water. Does the ...
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69 views

Convective heat transfer coefficient for counter-current flow

This is not a counter-current heat exchanger. It is two phases, Gas and Water, flow in one flow path but in opposite direction. I have found many source doing analysis on flow pattern of the ...
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41 views

Standard Heat of Combustion

When considering tabulated standard values of heat of combustion (∆H° combustion) or any other similar value, the results are reported for species in their standard states (1 bar pressure, 25°C, etc). ...
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35 views

Minimizing Availability vs. Maximizing Entropy

What is the conceptual difference between minimizing the availability of a thermodynamic system and maximizing the entropy of a thermodynamic system? I am under the impression that these are the same ...
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235 views

Caculating thermal stresses in a composite rod

The Question Between two rigid walls separated by a distance $l_1+l_2$, two rods of equal cross-section area $A$, and length, coefficient of linear expansion and Young's modulus $l_1, ...
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Finding out the temperature difference

If we add 10 spherical bubbles then there will be some change in their area. Is there any way to find out change in temperature of the liquid from the change of its area?
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52 views

Heat transfer in a cylinder with two insulators

I'm used to problems which ask me to find the heat transfer when, for example I have a very long cylinder covered with an insulator, each with their respective conductivity coefficient. I'd use the ...
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167 views

calculating heating effect of coil submerged in hotwater tank

i would like to estimate the temperature increase of water passing through a heating coil submerged in a hotwater tank, i know the cold flow and temperature and the temperature in the tank, as well ...
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294 views

Ultra-Relativistic Fermi Gas - Chemical Potential and Energy

I tried deriving the expression for chemical potential of a Relativistic Fermi Gas using asymptotic expansion (for large z) in : $$ N = \frac{V}{h^3}4\pi (KT)^3g_s \int \frac{p^2 dp}{e^{p-\nu}+1} $$ ...
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How to do Legendre transformations on a S=S(U,V) P,V,T system?

Problem: For a $P,V,T$ system with constant mass,entropy can be considered a function of $U,V$, i.e. $S=S(U,V)$. The goal is to derive the rest of the thermodynamic functions via Legendre ...
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210 views

Find state equation given cubic expansion and isothermal compressibility coefficients

Context: I'm studying basic thermodynamics. Since I'm not confident that I translate the terms correctly, let me define the following coefficients mathematically: \begin{equation} \beta = ...
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Transient conduction - Biot number with irradiation?

I understand that the Biot number is essentially the ratio of the convective effects to the conductive effects in transient conduction but what if there is some sort of radiation from a heat source ...
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When heat is rejected by a system what will be $q$ according to sign convention?

When a system rejects heat it can be assumed that work is done by the system. So as per law the sign convention must be negative. But my physics textbook says the reverse. So is the question.
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(Iso-baric / iso-choric) Thermodynamic cycle question

A very simply question: Is something that even somewhat resemble a thermodynamic cycle consisting of two iso-baric and two iso-choric cycles possible (such that you get a simple rectangle representing ...
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Work of an adiabatic/ compresion: sign?

As far as I am concerned the adiabatic work it is given by: $$ W_{adi}=\frac{P_{f}V_{f}-P_{i}V_{i}}{\gamma -1}$$ While I have seen in other examples that it is used with $1-\gamma$ in the ...
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138 views

Is the thermal time constant simply the heat capacity divided by thermal conductivity?

My professor gave me this temperature decay data to make an exponential fit and told me that the time constant tau should be heat capacity over thermal conductivity. I'm looking at the wikipedia page ...
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What creates black streams in fountain-type fireworks?

For the New Year celebration of 2014, my nephews set off a series of fountain-type fireworks (as shown below). When one looks carefully into the shower of light, one notices that a fair number of ...
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How does pressurized gas constantly push?

If a gas, such as hydrogen, is pressurized into an air tight container, a force in terms of pascals (or whatever unit you want to use) is exerted, correct? That is what pushes against every surface ...
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98 views

Can I make a cold air trap (thermal equilibrium)

Thermodynamic buoyancy. I have an air intake for combustion air entering into a basement furnace room. During cold weather, the air enters unchecked (no damper on pipe is allowed). I have this 5 ...
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54 views

Equilibrium Condition

In classical thermodynamics, equilibrium conditions means maximum entropy for a closed state. However, people always talk about equilibrium for open systems as well. How can one say that an open ...
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NPT simulations: what is the inertia of volume fluctuations (using periodic boundary conditions)?

NPT molecular dynamics (MD) are most often implemented by adding some kind of piston that regulates the pressure. The inertia of this piston determines the dynamics of volume fluctuations in the ...
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How does this Stirling engine work?

I'm looking at this Stirling engine, which I believe is a variation of an alpha type. It was developed by Nasa back in the 1980's. The thing is, I can't figure out how the hydrogen cycles through the ...
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78 views

Radiant barrier effect on inside of a hot water tank

I am trying to determine if a radiant barrier on the inside of a hot water tank would increase its insulating value. Normally radiant barriers are used in house construction to reduce heat loss by ...