Read about thermodaynamics | 110 Discussions | Page 1

  1. T

    A special case of the grand canonical ensemble

    In addition to the homework statement and considering only the case where ##U= constant## and ##N = large## : Can we also consider the definition of chemical potential ##\mu## and temperature ##T## as in equations ##(1)## and ##(2)##, and use them in the grand partition function? More...
  2. B

    Simulate the temperature inside an aquarium tank

    there's a website to size an aquarium heater or chiller. This is just for learning purposes (not for fish) but I have modified these parameters from default to perform a load calculation on a 100 gallon glass tank... For the tank temperature range I set to be between 150-160 degree F. and a...
  3. Zaya Bell

    B Thermal radiation's origin

    If a substance gains energy, it's molecules vibrate faster and thus the material increases temperature. My question is if heat lost through any other means but radiation is zero, how exactly does these molecules radiate photons?
  4. E

    Engineering Second law of Thermodynamics calculations for a heat engine – refrigerator combination

    For the heat engine: First I converted all the temperatures to Kelvin, ηmax=1-(333)/(1000)=0.667 ηclaim=(1*10^3)/(1.75*10^3)=0.5714 So the heat engine seems to be less efficient than a Carnot heat engine which means it can exist. For the refrigerator: COPmax=(253)/(363-253)=2.3...
  5. Sokolov

    I Integration of inexact differentials in Thermodynamics

    In Thermodynamics, I have seen that some equations are expressed in terms of inexact differentials, ##\delta##, instead of ##d##. I understand that this concept is introduced to point out that these differential forms are path-dependent, although I am not clear how they can be handled. So, are...
  6. Prabs3257

    Carnot engines in series

    I know i have to use the efficiency formula and everything is fine but i dont know how to find T its the only unknown in my equation can someone please tell me how to find T . In the solution they got the value of T by equating the work done by the two engines , but why is their work done equal ???
  7. kendreaditya

    I How much time is needed for a copper block at 0C to reach equilibrium with 75C water?

    I have a copper cylinder that is at 0C, how much time will be needed for it to equilibrate with 10kg of water at 75C? Copper cylinder: Mass: 105.7 g Specific heat: 0.385 J/gC Initial Temp: 0C Final Temp: 75C ish SA: 25 cm^2 Water: Mass: 10000g Specific heat: 4.184 J/gC Initial Temp: 75C...
  8. T

    Understanding energy losses in a compressed air system

    When measuring pressure drop across a compressed air system shown in the included figure, I get different results depending on the system downstream of the actual component I am measuring pressure drop across. Btw this is a real experiment that has been ran. The numbers below are different but a...
  9. P

    A Can decoherence be associated with heat generation?

    This question is inspired by a comment that @thephystudent made where he said that "The dephasing between the Bragg pulses is not unitary, I believe it can be explicitly written in Lindblad form and generates heat. I believe this Point of view is the same as (among others) the papers of...
  10. A

    Quasi-equilibrium process

    I am self studying thermodynamics and I stumbled upon the concept of a quasi-equilibrium process which I dont fully understand but here are my thoughts, Equilibrium is a condition of balance characterized by the absence of driving potentials and at such conditions you can measure properties that...
  11. L

    Thermodynamic Systems - Volume, Final Pressure and Final Temperature

    Mass = 0.12kg Initial temp = 500°c = 773K Initial pressure = 0.8 MPa = 800,000 Pa Final volume = 90L R = 287 Jkg^-1K^-1 1) Initial Volume V=mRT/P 0.12 x 287 x 773 / 800,000 = 26,662.12m^3 2) Final Pressure P2 = P1P2^1.2/V2^1.2 800,000 x 26,662.12^1.2 / 90 = 1,816,095,330 Pa = 1,816 MPa 3)...
  12. Parzeevahl

    Melting of substance with -ve slope for fusion curve

    The question says that the process is melting, so temperature must increase. Hence, Delta T > 0. Also, it is given that the slope for its fusion curve is -ve, which means that as we increase temperature, the pressure will decrease. So, Delta P < 0. The question asks to prove that the substance...
  13. santimirandarp

    I Types of Heat

    The question is: why ##dq_{surr}=-dq_{sys}##? q=heat, surr=surroundings, sys=system. Is there any simple way to understand this?
  14. J

    Work and Internal Energy for Adiabatic Processes

    Using (2) on (1) give ## dU = -dW##... (4) A.For expansion since the gas goes from ##(P_1, V_1, T_1)## to ##(P_2, V_2, T_2)##, does this imply ##T_1 \leq T_2 ##? B. If so, then ##W## for adiabatic expansion would be negative (using (3))? Using negative ##dW## in (4) gives us a positive result...
  15. V

    I Unknown formula

    What is this formula? q=λ⋅S⋅∪_x What does s and lambda mean?
  16. T

    B Temperature regulation in Earth orbit

    If I had an object in an orbit around the Earth that I kept continually shaded from the sun, how cold would it get? Assuming the shade device was not physically connected to and was sufficiently far away from the object to not radiate any heat to it. And if I actively adjusted how much shade...
  17. C

    What is the intuitive meaning behind the polytropic process.

    What does it actually mean from an intuitive standpoint? I don’t want to simply memorize the equation. What is it really and when can it be used? What is the usefulness of it? Thanks.
  18. T

    Efficiency of a heat engine

    Homework Statement I am having an issue trying to decipher this question, as I am not sure if it a lack of knowledge on my half or there is an assumption I have to make. Homework Equations ##\epsilon=\frac{W_{total}}{Q_{in}}## The Attempt at a Solution My issue is calculating the heat...
  19. D

    Air Compressor Model Analysis

    I have an interest in storing, for later use, energy from excess shaft power developed by a wind turbine. Currently I am assuming that the compressor is running in a steady fashion, continually drawing 300K, 1.0 atm. air into the compression chamber and compressing it to 20 atms. before...
  20. S

    I Why is there no maximum temperature?

    Given that absolute zero is the lowest temperature possible, were all particles have zero vibration. And given that the speed of light is the highest speed any object, particle, sub atomic or not can travel. Using 2 of the most fundamental laws of physics thermodynamics and general relativity...
  21. E

    B Why does the entropy of the Universe always increase?

    i dont really understand why S of the universe must be always positive,i know that only reversible process have constant entropy but why real proceses always increase S in the universe? sorry for bad english im not from USA or UK
  22. L

    I What is the relation between chemical potential and the number of particles?

    Chemical potential is defined as the change in energy due to change in the number of particles in a system. Let we have a system which is defined by the following Hamiltonian: $$H = -t \sum_i^L c_i^\dagger c_{i+1} + V\sum_i^L n_i n_{i+1} -\mu \sum_i^L n_i$$ where ##c^\dagger (c)## are creation...
  23. Raihan amin

    Shape of a bubble inside a rotating container

    1. A closed cylindrical vessel filled with water (at room temperature) contains a small air bubble of normal pressure and volume ##V=1~{cm}^3## inside in it.The cylinder is then started to be rotated slowly with a small angular acceleration in a complete weightlessness (at a space station)...
  24. G

    The Clausius-Clapeyron relation to study pressure cookers

    The Clausius-Clapeyron formula is given by \frac{d P}{d T} = \frac{L}{T \Delta V} where P and T are the pressure and temperature at the boiling point, respectively, and L is the latent heat per mole at the boiling point, and \Delta V is the change in the volume per mole between the gas and...
  25. Baibhab Bose

    Molar entropy of a metal

    Homework Statement [/B] What is the contribution of the conduction electrons in the molar entropy of a metal with electronic coefficient of specific heat? I cant figure out how to comprehend this, which relation/theory might lead to this? and How this answer is relevant to the point of molar...
  26. beefbrisket

    I Assumed value of pressure during quasistatic compression

    My text (Ian Ford - Statistical physics) describes an ideal gas system in a piston being quasistatically compressed by a piston head of area A under external force f. It assumes the system has a uniform pressure p. All good so far. Then it says: "the force pA equals the applied external force f"...
  27. P

    Explaination of Solid-Liquid and Solid-gas surface tension

    I am a high school student and currently studying Mechanical properties of fluid. We are taught surface tension in a very introductory level and most of it is about liquid-gas surface tension. We are taught that liquid-vapour tension is the atrractive forces that water molecules experience at...
  28. EastWindBreaks

    Do we assume the mixing chamber has an outlet?

    Homework Statement Hot and cold streams of a fluid are mixed in a rigid mixing chamber. The hot fluid flows into the chamber at a mass flow rate of 5 kg/s with an energy in the amount of 150 kJ/kg. The cold fluid flows into the chamber with a mass flow rate of 15 kg/s and carries energy in the...
  29. A

    Power output of a intercooler and turbocharger

    Homework Statement The power output of an automobile engine is directly proportional to the mass of air that can be forced into the volume of the engine’s cylinders to react chemically with gasoline. Many cars (like a 2008 Mini Cooper S) have a turbocharger, which compresses the air before it...
  30. Sizhe

    Book(s) to fill the gap from intro thermo to nonequilibrium thermodynamics/statistical mechanics

    Hi, guys I have posted this question on StackExchange, but no one seems to care answer. Because I don't think this is a simple textbook question, I start my thread here: I know this is a big question. But as a graduate student, my research is somehow related to nonequilibrium...