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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Calculate heat loss of aquifer with unknown shape

I am trying to calculate the heat loss of an aquifer. An aquifer is basically a hot-cold storage $80\: \mathrm{meters}$ under the ground. It is an open system and utilizes groundwater. By pumping for ...
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218 views

Explain to me how this water cooler works?

Goodday all, I was recently reading up on a few projects that might be of interest to me when I found "CPU Bong water coolers", there isn't much online on them so I figure I would ask y'all. If you ...
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427 views

what's the difference between linear n-atom molecule and nonlinear n-atom molecule?

I am reading a material about the degree of freedom for linear n-atom molecule and nonlinear n-atom molecule. Here is my analysis for a diatomic molecule, if there are two atoms, we have to use 3 ...
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31 views

Henry's Law in metals

For fixed temperature the concentration of a gas dissolved in a solution is directly proportional to the gas pressure $p$, i.e. $c_s (T,p) = f(T)p$. Since $H_2$ only dissolves in metals as single ...
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98 views

What temperatures can be reached in an air-to-air thermocompressor nozzle and why?

People are generally of the opinion that the boiler injector cannot be redesigned to run on air. In other words, an air-to-air thermocompressor that puts fresh air into a tank without a mechanical ...
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970 views

Joule-Thomson effect of Van der Waals gas

I'm supposed to calculate the inversion pressure $p_i$ of a Van der Waals gas. The state equation of the Van der Waals gas is: $$(p + \frac{a}{V^2})(V-b) = RT.$$ To get a hold of the inversion ...
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390 views

Difficulties with understanding total entropy change and unavailabillty

Of course, I know the fact that the entropy of an isolated system never decreases. Neverthless what makes me confused about the entropy(or change of entropy) of an isolated system is the explanation ...
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281 views

Rotational Constant and Moment of Inertia of Fluorine gas

I have come across some homework question on thermodynamics which needs me to calculate $B$ of $F_2$ My attempt: $B= \frac{h}{8\pi^2cI}$ where $I=\mu r^2=\frac{m_1m_2}{m_1+m_2} r^2$ Atomic mass of ...
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92 views

How to solve state parameters using these givens for an ideal gas?

In a thermodynamic turbine using air as an ideal gas, given that you have a known inlet temperature value $T_i$, a known exit pressure value $P_e$, a known inlet and exit velocity $V_i$ and $V_e$, a ...
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133 views

How much money does an unused but plugged-in cellphone-charger waste in a year, if its not getting warm?

Is it right as xkcd states: You can use heat flow to come up with simple rule of thumb: If an unused charger isn’t warm to the touch, it’s using less than a penny of electricity a day. Or, more ...
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49 views

Height of a piston in a heated cylinder containing H2O

I'm a first time user and I hope I won't be too enigmatic asking the following question: I have a cylinder (radius= $6$ $\text{cm}$) with a frictionless piston on top of it and inside $30$ $g$ of ...
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75 views

Several questions about spring chiller and LMTD

I'm designing a simple copper coil wort chiller. Digging formulas I'm having hard time to figure some things out, perhaps some simple guides may help me to go the right direction: LMTD need inlet ...
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45 views

Free Energy and quantum measurement

Free Energy must be expended to reset the state of an measurement apparatus. Is this statement valid in all situations? Is there a Definitive mathematical exposition?
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119 views

“This is not a perpetual motion machine, because reservoir temperatures are changing.” Is it a valid argument?

I've already faced this situation several times: given a statement (in area of thermodynamics) I used it to provide an example of some perpetual motion machine (of first or second kind). Therefore, I ...
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57 views

Temperature measurement, precision

I am having problems with one of the problems I have done (a) which is basically $\theta = 273.16K (19/15) = 346.00K$ For (b) I am given that the length is 15.00cm when the thermometer is incontact ...
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43 views

What is the fluid approximation for BCS action?

For a system with free fermion gas at finite density (i.e. free Dirac action), we have an ideal fluid description with rho, p, n. What is the fluid description for BCS action? Suppose we have a box ...
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206 views

Centrifugal Compressor Flow Rate

For a centrifugal compressor, as found in most turbochargers on internal combustion engines, is there a noticeable change in flow rate versus a naturally aspirated flow rate? In other words, does the ...
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301 views

Is the $mL_c$ value for triangular and rectangular fins the same value?

I am looking at the solutions that my professor put up and I feel that he did something wrong. Here is the question and I will give my stab at the solution so you can see why I think that it is wrong. ...
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367 views

How equivalent are heat energy and work energy in connection with a spinning flywheel?

Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper. Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
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62 views

How many times brighter could the stars shine without raising the temperature of space?

If my understanding is correct, the temperature of space (as defined by the temperature that a black-body will reach) has been decreasing since the big bang. It has never increased. Additionally, ...
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531 views

Do the properties of two streams flowing into an engine add together when they mix?

Let's say I have two stream supplys that have separate mass flow rates, enthalpies, and velocities that flow into an engine. Upstream of the engine's inlet, the two streams mix to form one stream that ...
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92 views

How to compute the heat flow for a specific material for some given boundary temperature?

Assume I have a bounded material with heat sources inside. The material is known (i.e. I know heat capacity and all relevant data) and the temperature of the boundary is fixed. I solved the (steady ...
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16 views

Heat engine efficiency, compression ratio vs temperatures

I want to understand the role or even existence of a cold reservoir in the Otto cycle gasoline engine. The efficiency of the Otto engine is given as a function of compression ratio $$ ...
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24 views

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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14 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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16 views

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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16 views

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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53 views

Heat equation : boundary conditions?

Say we have a bar centered at $x=0$, that is heated. We have the 1D Heat equation which we can solve to find a parabolic temperature profile : $$\kappa \frac{d^2 T}{d x^2}=-\frac{Q}{L S}$$ with ...
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32 views

Irreversible heat engines strictly less efficient than reversible ones

I undertand how Canot's theorem implies that irreversible heat engines must be no more efficient than reversible one's, but it isless clear why they need to be less efficient, as I have seen stated in ...
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24 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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17 views

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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21 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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20 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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35 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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35 views

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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15 views

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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51 views

Do reversible processes exist in Nature?

Classical thermodynamics always discusses entropy in the light of reversible processes, and it lies at the heart of the definition of entropy. But do these reversible processes exist in Nature, or are ...
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10 views

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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38 views

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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50 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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16 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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39 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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26 views

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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30 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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46 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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37 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 ...
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59 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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33 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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70 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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27 views

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 ...