Thermodynamics Definition and 1000 Threads

Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, radiation, and physical properties of matter. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also in other complex fields such as meteorology.
Historically, thermodynamics developed out of a desire to increase the efficiency of early steam engines, particularly through the work of French physicist Nicolas Léonard Sadi Carnot (1824) who believed that engine efficiency was the key that could help France win the Napoleonic Wars. Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency."
The initial application of thermodynamics to mechanical heat engines was quickly extended to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged. Statistical thermodynamics, or statistical mechanics, concerns itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a purely mathematical approach in an axiomatic formulation, a description often referred to as geometrical thermodynamics.

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  1. JamesB93

    Thermodynamics: SFEE Homework Solution

    Homework Statement This is a question from an exam that my university determined to be so harsh that they allowed resits with uncapped grades. I'm going to be taking such a resit thus I'm trying to figure out the paper: Air at 10oC and 80 kPa enters the diffuser of a jet engine steadily with...
  2. davidge

    Fundamental thermodynamics relation

    I was looking at the fundamental equation ##dU = Tds - Pdv + \sum_i \ \mu_i \ dN_i## and I was thinking of how many different ways one has for deriving it. I know I have to look through a book on Thermodynamics. I actually have done that some time ago and I will do that again. But the following...
  3. D

    How Is Actual Power Calculated in a Turbine with Given Isentropic Efficiency?

    Homework Statement Steam at a pressure of 4 MPa and 400 C and flow rate of 10 kg/s is expanded in a turbine to a pressure of 10 kPa. If the isentropic efficiency of the turbine is 0.85 then the actual power produced by the turbine is? Homework Equations :[/B] ηt= (m(h1-h2))/(m(h1-h2s)) = (W...
  4. J

    Carnot cycle - Zero Power Extremes

    Hey guys, I ran into this paper talking about the Maximum power you can obtain from a Carnot cycle: http://aapt.scitation.org/doi/abs/10.1119/1.10023 From what I understood, there are two extremes. To achieve maximum efficiency you have to make sure that the temperature of the system is never...
  5. V

    Thermodynamics, bullet melting ice problem

    Homework Statement An ice cube at the melting temperature that has a mass of 20 g, is struck by a bullet with a mass of 9 g, flying at a certain speed. Determine the speed of the bullet, if it is known that one third of his energy was consumed to break the ice, and the remainder to melt it...
  6. T

    Thermodynamics: The Jet Engine

    Good evening everyone,I had several questions regarding basic thermodynamics. After going to Paris Airshow (Le Bourget), lot's of questions came to my mind after looking at those beautiful Jet engines...I have always had a very basic understanding on these engines: a fan, a compressor (High and...
  7. A

    Thermodynamics -- Entropy of an Isometric Process

    In order to better explain my question let me give a precise situation and then state my question Say I have a well insulated rigid container containing some mass m of a saturated liquid-vapor mixture of water at some pressure P1. Initially it's at some quality x1. An electric resistance heater...
  8. V

    Thermodynamics cycle work question

    Homework Statement A mass of gas occupying volume V1 = 2 m3 at the pressure P1 = 4*10^5 Pa performs the cycle represented in the Figure that i have uploaded.What is the work of gas in this cycle, knowing that the pressure P2 = 10^5 Pa Homework Equations Work=1/2 * (P1 - P2) * (V1 - V3) The...
  9. i_hate_math

    Second law of thermodynamics and absolute zero

    Does a system with zero entropy represent the thermal equilibrium at some temperature = 0K? Does the second law of thermodynamics entail that the system will eventually evolve to higher entropy? e.g. a system of 7 magnetic dipoles of paramagnetic spin-1/2 particles in an external magnetic...
  10. A

    A Re-interpretation of the third law of thermodynamics

    Consider the first paragraph of this paper - https://arxiv.org/abs/gr-qc/0611004: A fundamental problem in thermodynamic and statistical physics is to study the response of a system in thermal equilibrium to an outside perturbation. In particular, one is typically interested in calculating the...
  11. Const@ntine

    Thermodynamics: Steam is added to an ice cube

    Homework Statement Vapors of 100 C is added to an ice cube of 0 C. How much of the ice cube has melted and what's the final temperature if the masses of the steam and the ice cube are 10.0 g & 50.0 g respectively? Homework Equations Lw = 3.33 x 105 J/kg cw = 4186 J/kg*C Q = m*c*ΔΤ Q =...
  12. J

    Temperature change (first law of thermodynamics)

    Hi, From the first law of thermodynamics it follows: Cp * (δT/δt) = (δQ/δt) where Cp = specific heat capacity, T = temperature, Q = heat, t = time From this formula, you would derive that temperature keeps on increasing as long as dQ/dt > 0. But if you, for example, look at the idealized...
  13. SciencyBoi

    Internal Energy of an Ideal gas related to Molar specific heat

    Homework Statement Please look at the below images which is the derivation of the relation between the internal energy of an ideal gas and the molar specific heat at constant volume. (Snaps taken from Fundamentals of Physics Textbook by David Halliday, Jearl Walker, and Robert Resnick) As...
  14. F

    Thermodynamics - isentropic, polytropic and compressibility

    Several questions: What does compression actually means? In the case of isentropic calculations a changed in density (or specific volume) is included in the calculations (isentropic.jpg) so isentropic means that compressibility is included in those calculations or what?In a previous thread, a...
  15. A

    How Does Adiabatic Compression Affect Air Temperature and Volume?

    . Consider a pump that is required to compress air in a factory. The cylinder in the pump has an inner diameter of 2.00 cm and length 60.0 cm. Air is drawn into the pump at atmospheric pressure and 18 degrees celcius and the pump adiabatically compresses the air to a pressure of 17...
  16. T dawg

    Courses Should I take a physics course over summer or is it cramming

    At my community college, the first calculus based physics courses (the predecessor to modern physics) are split into 3 semesters: mechanics, electromagnetism, and thermodyamics/light. As long as you take the mechanics part first, you can choose which one to take next. This summer session is 8...
  17. PePaPu

    Thermodynamic assembly - Statistical Thermodynamics

    Homework Statement Consider a model thermodynamic assembly in which the allowed (nondegenerate) states have energies 0, ε, 2ε, 3ε.The assembly has four distinguishable (localized) particles and a total energy U = 6ε. Tabulate the nine possible distributions of the four particles among the...
  18. M

    Computation of maximum pressure in heated closed vessel

    I have a relatively simple design problem but my memories of thermodynamics are very rusty and I can't figure it out on my own. To make it short, I want to put a mix of solid, water and air in a 500mL pressure vessel and heat it all up to 250'C for several weeks. T and P are at room conditions...
  19. B

    B What is the comparison between the Born rule and thermodynamics?

    Some say there is analogy in the Born rule in thermodynamics where the particles locations depend on the probabilities. In QM, the amplitude square is where you have the probability of the particles being there. How about in thermodynamics.. what is the counterpart of the Born rules, and what...
  20. shihab-kol

    Does Building Construction Defy the Second Law of Thermodynamics?

    From what I know, the law says that disorder increases over time. But, when a building is constructed the disordered bricks,cement etc. take form of the ordered building. Am I wrong or is this an exception?
  21. PHstud

    Proof of fundamental thermodynamics equation for open systems

    Hi ! I'm having a bit of trouble understanding something. Let 'u' be internal energy, 'h' enthalpy, 'e' work and 'q' heat. ('r' are dissipations and 'S' entropy) From a book , i read that de+dr=PdV= -du + TdS This seems to stand for closed cycle. Yet, my teacher uses the formula de+dr=vdP=...
  22. oobgular

    How Does Altitude Affect Humidity Sensor Readings?

    Homework Statement So I sent a humidity sensor up in a weather balloon, which gave a reading for relative humidity. I eventually want an absolute humidity, but I am unsure whether I need to correct the output based on the changing density and atmospheric pressure with altitude. Homework...
  23. G

    The relation between the energy minimum and entropy maximum

    Hi. This is the problem 5.1-1 from the second edition of Callen's Thermodynamics. It says Formulate a proof that the energy minimum principle implies the entropy maximum principle. That is, show that if the entropy were not maximum at constant energy then the enrgy could not be minimum at...
  24. yecko

    Chemistry: First principle of thermodynamics

    Homework Statement https://holland.pk/uptow/i4/1ca04ddf7c25f6c63e307720c34a4ff3.png Homework Equations First principle of thermodynamics: E=q+w The Attempt at a Solution E=q+w=-17+21=4kJ>0 ∴Endothermic (absorb heat from surrounding) (a) false (from surrounding to the system) (b) false (does...
  25. B

    Maximum work done in a Carnot Cycle

    Given that in a Carnot Cycle the two adiabatic processes are essentially equal and opposite in magnitude the total work done by the cycle is in the two isotherms. The total work of the system is generally given as -NR(Th-Tc)ln(Vb/Va). Does this mean that the work done by a monatomic ideal gas is...
  26. M

    Naive Doubt About Thermodynamic Equilibrium

    This is more of a recurring conceptual doubt that I keep on running into when solving thermodynamics problems. We are taught that variations between extensive state variables in equilibrium are given by the following 'fundamental formula': dE = TdS + \mathbf{J}\cdot{d}\mathbf{x} +...
  27. C

    Calculate the moisture content of air

    Homework Statement (Simplified) During tests at cliffside power station, the following data was recorded from the cooling tower. A cooling tower has a 9 cell draft design, each diameter is 10m. Data D_o = 10m V_exit = 14.4 m/s T_exit(15 celsius) = 288.15K Ambient conditions : T(15 celsius) =...
  28. L

    Thermodynamics. Partial derivative tricks.

    If we consider function ##z=z(x,y)## then ##dz=(\frac{\partial z}{\partial x})_ydx+(\frac{\partial z}{\partial y})_xdy##. If ##z=const## then ##dz=0##. So, (\frac{\partial z}{\partial x})_ydx+(\frac{\partial z}{\partial y})_xdy=0 and from that \frac{dx}{dy}=-\frac{(\frac{\partial z}{\partial...
  29. knc

    Heat transfer in series and parallel

    Homework Statement Homework Equations P = k A \frac{dT}{dx} The Attempt at a Solution a) Assuming steady state transfer, energy transfers through rods at the same rate everywhere. Letting T be the temperature at the point of welding. P_1 = k_1 A \frac{T_h-T}{L} \\ P_2 = k_2 A \frac{T -...
  30. L

    Why Do Authors Use γ=γ(P,T) Instead of γ=γ(P,T,V) in Thermodynamics?

    Thermal coefficient of pressure is defined by \gamma=\frac{1}{P}(\frac{\partial P}{\partial T})_V . Why in books authors uses ##\gamma=\gamma(P,T)## and no ##\gamma=\gamma(P,T,V)##. Could you explain me this. I am sometimes confused with this dependences in thermodynamics.
  31. Pull and Twist

    Calculating work of Otto cycle stages - Thermodynamics.

    One big coincidence of thermodynamics is that automobiles are usually powered by an Otto cycle This cycle consists of an adiabatic compression (the cylinder compresses), isochoric compression (the fuel ignites, increasing the temperature in too short a time for the piston to move), adiabatic...
  32. W

    Thermodynamic cycle of a solar cell

    Mechanical Engineering Undergrad here: So this didn't seem explicitly like a homework question, but I was wondering how to describe a solar cell in terms of thermodynamics. If I had to model it with the first law of thermodynamics, I would consider it a simple loop of heat/work exchange...
  33. Ali Ahmad

    Steam generation thermodynamics

    a cylindrical tank with volume V a volume of water is inside the tank and the rest is air now if coal combustion is releasing heat into the tank Qin and when the gauge reads a certain pressure "P", the valve is opened which allows steam to exit the boiler what's the mass flow rate of the steam?
  34. S

    Assumption of local thermodynamic equilibrium in a fluid

    Moving fluids are generally in a state of non-equilibrium. However, in fluid dynamics, people generally assume a state of local thermodynamic equilibrium and argue that in such a condition, equilibrium thermodynamic concepts such as pressure, temperature, entropy, internal energy etc. can be...
  35. A

    Conservation of entropy -- adiabatic process

    Hello.I have a question about entropy of a thermodynamic system. 1)If we have let say a gas that is separated by some thermo isolated walls (so no heat goes in or out) does the entropy of that gas conserve? I taught that if S=dQ/dt, because Q=0,then the entropy should be conserved. 2)So,does the...
  36. S

    Understanding Internal Energy Changes in Phases of Water

    Homework Statement Sketch a diagram of internal energy (y-axis) versus temperature in the range from -10°C to +112°C to indicate how energy would change for a fixed quantity of water in its three phrases. Label and explain the main features of the variation. Homework Equations The Attempt at...
  37. M

    Gas Compression in a Closed System: Non-Linear vs. Horizontal P-V Diagrams

    When a gas in a closed system is compressed, should the graph always be non-linear? If T is constant ie if the process isothermal it is clear that it should be so but I am not very sure that if the graph can be horizontal. If T decreases might not it be horizontal? Thank you.
  38. S

    Confusion regarding the First Law of Thermodynamics

    Is forcing a closed system to expand (e.g. by pulling out a piston), causing it to cool, work done to the system or work done by the system? I assume it was work done to the system, but that means the first law of thermodynamics formula no longer balances if you assume an adiabatic change...
  39. T

    How Long Should My Double Pipe Heat Exchanger Be for a 22kW Capacity?

    I'm trying to design a double pipe heat exchanger for two different water lines. One line is chilled water of approximately 7degC and the other is chilled water return from an air handling unit, of around 12degC. I want to design this heat exchange for a capacity of approximately 22kW. The part...
  40. S

    Thermodynamics Question Regarding assuming Irreversibilities

    Homework Statement There exists a tank filled with air with a given volume, temperature, and pressure. The tank exists in a room at a given temperature and pressure. That is: For the tank: P=1MPa, T=700k, V=1m^3 Outside: T=295K, P=100kPa Homework Equations \psi 2-\psi...
  41. Dennis Plews

    A Non-locality and The First Law of Thermodynamics

    I'm sure I read somewhere in my physics books that non-locality is required in order to maintain the integrity of the 1st Law of Thermodynamics. Is that correct? If so, that seems to require one or more additional spatial dimensions via which the total amount of energy is maintained. What...
  42. T

    Approaching Reaction Feasibility: Thermodynamics and Equilibrium Constant

    How would one approach part I and II? In terms of thermodynamics I'm not sure how I can show that this hypothesis is true. Could I work out the equilibrium constant and make a decision based on its magnitude? For example if it is >>> 1 then the hypothesis is true, would that be correct? For the...
  43. W

    Helmholtz and Gibbs free energy for an adiabatic process

    Homework Statement Calculate changes in A and G of one mole of an ideal gas that undergoes the following processes respectively. 1. adiabatic expansion from (T1, P1) to (T2, P2) 2. isobaric expansion from (P, V1, T1) to (P, V2, T2) (if it is not isothermal) 3. isochoric expansion from (V, P1...
  44. M

    Programs for thermodynamics calculations

    I know these calculations in thermodynamics can be done by hand or a simple calculator but I wonder if some programs do these calculations. These programs might be called multiphysics programs. An example of a calculation - select piston-cylinder arrangement. -enter initial...
  45. J

    Condition for condensation from adiabatic expansion

    Homework Statement I'm stuck on part (c) of this question. Homework Equations $$T\frac{d}{dT}\bigg(\frac{L}{T}\bigg) \equiv \frac{dL}{dT} - \frac{L}{T}.$$ Clausius-Clapeyron equation: $$ \frac{dp}{dT} = \frac{L}{T\Delta V} \approx \frac{L}{TV_{vap}}.$$ The Attempt at a Solution My approach...
  46. Adam Rabe

    Thermodynamics question: temperature between layers

    Homework Statement Homework Equations h = k/d 1/h (total) = 1/h + 1/h + 1/h... + 1/h (surf) Q/t = h A T The Attempt at a Solution For the thermodynamic one i got up to calculating the total heat transfer coeffecient but i don't know where to go from there as its asking for the outside...
  47. T

    Derivation: Entropy of Vaporisation using Redlich-Kwong EoS

    Homework Statement For some reason it is not letting me add the image here, here is the link to the question: http://imgur.com/a/3DLWM The part I'm stuck on is the last part. Basically, the question is to obtain the following equation for the entropy of vaporisation using the Redlich-Kwong...
  48. Jarro

    Stirling engine against solar panels

    Hello, Since childhood, I have been wondering why it is not possible to make miniature electric motors with pistons and gas container covered with a very dark (meaning high absorption coefficient over a wide spectral width) material that would translate the energy of sunlight directly into...
  49. D

    Thermodynamics of a cannon ball / musket ball shot bullet

    I am a computer scientist currently writing a 3D simulation for high speed projectiles both sub and supersonic for various shapes and sizes of projectiles. For now I am focused on completing simulation of a simple model of a round ball shaped projectile (ie a cannonball or musket shot). I like...
  50. asteeves_

    Solve Entropy Gen of Water-Ice Contact, 100J Transferred

    Homework Statement 5 kg of water at 60 degrees are put in contact with 1 kg of ice at 0 degrees and are thermally isolated from everything else. The latent heat of ice is 3.3x105 J/kg. What is the change of entropy of the universe when 100J of energy are transferred from the water to the ice...
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