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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(Chemistry) Dimensionless heat transfer coefficient

I'm trying to reproduce in Matlab the model of a continuous stirred tank reactor (CSTR) that I've gotten for a project. The model is written in the state space and uses some dimensionless values, ...
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38 views

Heat generated by collision

Suppose there are two objects: A = m1 and B = m2 . A is travelling at a constant velocity v toward B and collides inelastically: is there a way in which I could determine the energy which is ...
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69 views

How do gas molecules constantly bounce without losing energy?

From a related question (How does pressurized gas constantly push?), i asked myself this: How do gas molecules constantly bounce off each other without losing energy? If you drop a ball, it bounces a ...
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18 views

Explanation for Homogeneous Nucleation Temperature?

What is homogeneous nucleation temperature (for water this is listed as -42C); is it simply the lowest experimental temperature you can go before supercooled liquid turns into solid, or is it that ...
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42 views

Phase diagram of water v/s other substances

Why for water increase in pressure decreases solidification temperature? The fusion curve of water is not same as that of other substances and for other substances specific volume increases during ...
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17 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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66 views

Why is cooling much harder than heating?

I'm trying to invent a distillation apparatus that runs solely on electricity. Suddenly, I realized that cooling things is really hard, while heating them up is so easy. Actually, it seems that there ...
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20 views

Thermodynamic equilibrium- mixing of gases

What is the final temperature and pressure after removing diaphragm of a cylinder which divides the cylinder into two equal components each of volume $0.1\,m^3$ and each component contains air at ...
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12 views

Unmixing of gases: What is the relevant temperature for my Entropy?

This answer to a question about unmixing gases states: However, let us now assume we have to hand a source of mechanical work, and a large heat reservoir at temperature $T$. I'll assume that ...
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103 views

Why does a bubble take a spherical shape?

I suspect this has something to do with thermodynamics and the isoperimetric inequality and I'm interested in a mathematical derivation of this result.
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19 views

How to calculate heat generated from cosmic dust in space? [duplicate]

Say I have a spaceship, and I'm flying it through space at a constant high velocity V. The spaceship is pretty large (big surface area). In space however, there is cosmic dust scattered throughout ...
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19 views

Why does the equation for effectiveness of heat exchangers have $C_{\text{min}}$ in the denominator?

For an ideal heat exchanger of infinite length, $$ Q_{max}=m_{h}C_{h}\left[T_{h,i}-T_{o}\right]=m_{c}C_{c}\left[T_{o}-T_{c,i}\right] $$ \begin{eqnarray*} m_{h}C_{h}T_{h,i}+m_{c}C_{c}T_{c,i} & ...
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21 views

A confusion on Radiations emitted from a body [duplicate]

Suppose an atom is accelerated...Now the protons in its nucleus and the electrons in the orbits are also accelerated...So will they emit the electromagnetic radiations? Basically here the electrons ...
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75 views

Is the amount of radiation you receive in space constant regardless of velocity?

I'm only in high school, so this will probably have fatal flaws. So basically in space, there is bound to be stray radiation, whether from the stars, or cosmic background, floating around right. And ...
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32 views

Temperature Gradient with varying $T$ [on hold]

I'm working on a problem which asks for the temperature gradient at the ends of the rod. The blocks (right and left) are both kept at 0 degrees C. The temperature of the rod is given by $T = ...
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64 views

Can you explain why crystals form without thermodynamics?

I know that the basic reason that solid crystals form is because it's the lowest energy configuration (i.e. this). I am looking for an intuitive explanation for this process, one that does not involve ...
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13 views

How do I set up the tridiagonal matrix for a heat diffusion with layers of different thermal diffusivity?

I have Scala code that recreates the Crank-Nicolson solutions for the diffusion equations, and matches 'Excel for Scientists and Engineers' (Joe Billo, Wiley). However, I would like to be able to ...
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19 views

Does no variables change in an adiabatic + isothermal system?

Adiabatic + isothermal = no heat and temperature change. Does that mean the system will remain as it is? If it is adiabatic + isovolumetric or adiabatic + isobaric , is it as well no change in any ...
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28 views

What is the difference between reversible and irreversible adiabatic expansion?

What is the difference between reversible and irreversible adiabatic expansion? Is it true that the work done by the gas is the same but the pressure applied externally differ between two process? ...
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23 views

Is it only possible when 600J of heat is exhausted and 400J of heat is converted into work? [on hold]

Is it only possible when 600J of heat is exhausted and 400J of heat is converted into work? Is the 600J heat will enter the cold reservoir and available to do work again? q1/T hot + q3 / T cold = 0 ...
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41 views

Why won't the efficiency of a heat pump increase when $T_\mathrm{cold}$ decreases?

Why won't the efficiency of a heat pump increase when $T_\mathrm{cold}$ decreases? In the carnot cycle, efficiency increases when $T_\mathrm{cold}$ gets colder and $T_\mathrm{hot}$ gets hotter. Are ...
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18 views

Comparison between isobaric, isothermal and adiabatic expansion

Please check if my understandings of these terms are right because they are a bit confusing to me. For all three types of expansions, a change in volume means work is done by the system to the ...
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32 views

For change in entropy dS = dq/T, is T the temperature of system or surrounding or both?

For change in entropy dS = dqrev/T, is T the temperature of system or surrounding or both? I am confused about Thot, Tcold, Tsys and Tsurr. If qrev, are we talking about the reversible cycle such as ...
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107 views

Does entropy have a physical meaning?

Entropy is incredibly useful as a mathematical tool. But what does it actually mean? I understand that the Boltzmann entropy is defined by: $$S=k\ln{\Omega}$$ With $\Omega$ being the multiplicity ...
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Why do computers generate heat?

Computers generate heat when they work. Is it a result of information processing or friction (resistance)? Are these just different ways to describe the same thing? Or does some definite part of the ...
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25 views

Temperature dependence for specific thermal diffusivity in the diffusion formula

I recently found this answer about the diffusion equation (nice one actually), but have one doubt about the temperature dependence of this formula. If the "packet" of energy (terminology suggested ...
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55 views

Is it possible for heat to flow from body having less heat energy to a body having more heat energy?

Is it possible for heat to flow from a body having less heat energy to a body having more heat energy?
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100 views

Disequilibrium during infinitesimal steps of a thermodynamic reversible process & cause of maximum work to be achieved during reversible process?

In almost every sites and even in my book,it is written that "Reversible process is the process which is carried out infinitesimally slowly so that in each step thermodynamic equilibrium is maintained ...
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Entropy changes with the reversible and irreversible expansion of an ideal gas [closed]

a) What is the entropy change for 1.00 mol of H2(g) that has undergone a reversible expansion from 0.01m^3 at 100K to 0.100m^3 at 600K. For hydrogen, Cp = 29.066-0.836x10^-3T+20.17x10^-7T^2 in ...
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75 views

Will 5 pizzas in the same Hot Bag stay warmer than 5 pizzas in 5 separate Hot Bags?

For example, say I am delivering 5 pepperoni pizzas to 5 different addresses. In one scenario, I Keep all 5 in the same insulated Hot Bag, I carry that bag to the door, and I quickly remove one of the ...
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2answers
34 views

Does the relation between entropy and temperature depend on the ensemble?

If we change the temperature of a given system, there will be a relation between its entropy and temperature S(T). Is S(T) the same in a canonical ensemble and a grand canonical ensemble? If not, is ...
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36 views

Alternative liquid for Galileo thermometer

So a friend of mine broke my Galileo thermometer recently. The glass tube and the liquid inside were lost, but the bulbs survived. I've cleaned out an old tall glass candle, and tried filling it with ...
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When the low temperture reservoir with negative temperture (Kelvin), such as Ising model, is the efficiency of ideal heat engine larger than 1?

The ideal Carnot engine works between two heat reservoir with two temperatures $t_h$ and $t_l$. Its efficiency is then $1-\frac{t_l}{t_h}$ . If the low temperture reservoir is the Ising model with ...
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Is it possible to cool magnetic dipoles with a magnetic static field?

Suppose you have a bath of magnetic dipoles, with a common mean rotational kinetic energy. Now you apply a very strong magnetic field so that the dipoles align with the field, thus "losing" their ...
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16 views

Final temperature of an air parcel

How would one find the final temperature of an air parcel ascending adiabatically in the atmosphere? Like which formula would you use? I used the equation of state for dry air to find the initial ...
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Dry adiabatic lifting

If an unsaturated air parcel ascends adiabatically in the atmosphere with an initial temperature, would the final temperature of the air parcel, when it reaches it's destination, be the same at the ...
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76 views

Thermodynamic reversible process

My book says "A process is said to be reversible if it is carried out infinitesimally slowly so that in each step thermodynamic equilibrium of the system remains unchanged & any infinitesimal ...
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1answer
64 views

A puzzle of thermalization in simulating the 3D XY-model

I am learning the classical Monte Carlo simulation. When I simulate the 3D XY-model $$ \beta H = -\beta J \sum_{<i,j>} cos(\theta_i-\theta_j) $$ where $\beta$ is the inverse of the temperature ...
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Creating correlated Szilard engines

A demon has a large number of boxes with a single particle in. He / she adiabatically introduces a wall in the box, dividing it in two with a particle in one of the two halves (L, R). The demon does ...
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A problem of thermodynamics [closed]

A rigid tank contains a hot fluid that is cooled while being stirred by a paddle wheel. Initially the internal energy of the fluid is 800KJ, during the cooling process, the fluid loses 500KJ of heat, ...
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21 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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1answer
41 views

How to calculate Gibbs free energy of diamond?

How the effect of crystal structure on Gibbs free energy is calculated? For example, how the Gibbs free energy of diamond is 2.9 kJ/mol, while that of graphite is 0?
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Specific volume of an air parcel [closed]

So I have an unsaturated air parcel in the atmosphere that ascends adiabatically from the $1000$ mb level to the $700$ mb level with it's initial temperature being $10$ degrees Celsius. I have to ...
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5k views

How close can you get to lava before burning?

As the title asks: How close can you get to lava before burning? I know that it depends on an number of factors; speed of lava flow, wind direction/strength, type(?) of lava flow (related to speed, ...
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3answers
141 views

Asymmetric heat conduction?

So I have this side-view drawing. Now I wonder, will such a multi-layer material have asymmetric heat conduction properties? Namely, because of radiative conduction, reflective aluminum surface ...
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3answers
79 views

Definition of Entropy in thermodynamics

In most textbooks, the definition of entropy in reversible processes on a system $S$ is given simply as $$d S=\delta Q/T.$$ It seems to me this definition is insufficient since it does not specify ...
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21 views

Simple modelling of seasonal variation of temperature?

I'm really curious about this: What is the simplest (or most simplified) differential equation that accounts for the variations of temperature throughout the year at some point on the northern ...
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22 views

Modeling a wine cooler heat loss to ambient

I'm trying to model the steady state heat loss to ambient, in W, for a wine cooler similar to the following: For the modeling, I will need the following variables/constants: $T_a$ [K]: Ambient ...
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26 views

Thermal emission cathode electron velocity distribution

I can't find any experimental data (or theoretical expression) on what is the velocity (or energy) distribution of thermal emission cathode electrons emmited from the cathode at approximately 2000 K ...
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226 views

What happens to the temperature when an ideal gas is compressed?

I am rather confused about this. I know from Charles' law that under constant pressure, the volume of a gas is directly proportional to its absolute temperature i.e. $$\frac{V_1}{T_1} = ...