Thermodynamic Definition and 502 Threads

I have to calculate the thermodynamic efficiency of a power station. I have to assume the cooling towers maintain 70 degrees C and hence the amount of electrical energy (in J) from one mole of methan. I've been given the enthalpy of combustion of Methane. I know the thermo efficiency is (sum of...

Hi, everyone ! I am a new member to PF but I find it helpful as people will give ideas and suggestions for me :) Recently,I come across something called as a magnetic motor. From the design, a few permanent magnets are placed on the edge of a circular disk. Then, as another magnet approaches...

Thermodynamic Cosmic Problem ! Ill start with the third law of thermodynamics which denies the existence of zero kelvin (as stated by my lecturer). Also i found out that the temperature of vacuum is 3k due to the radiations left over from the Big Bang. However the space(or the absolute vacuum)...

Homework Statement This question is about entropy of magnetic salts. I got up to the point of finding H1, the final applied field. The Attempt at a Solution But instead of doing integration I used this: dS = (∂S/∂H)*dH = (M0/4α)(ln 4)2 I removed the negative...

In a lot of practical situations it is simply assumed the canonical and microcanonical ensemble give the same predictions, and that's fine, but I'm interested in a more exact statement of when they are indeed equivalent (in the thermodynamic limit). First of all, a thermodynamic limit must...

This is about the basic thermodynamic cycle of the gas turbine (i.e. Brayton or Joule cycle), consisting of adiabatic compression, heat addition at constant pressure, adiabatic expansion, and heat rejection at constant pressure, and the standard ways of analysing this through Pressure-Volume...

dE = TdS - PdV, or equivalently \Delta E = \int T \mathrm d S - \int P \mathrm d V In general this is said to be derivable in the reversible case, however since S and V are state variables, it's also true for the irreversible case. But it can't be true for any irreversible case, since the...

dE = dQ + dW = dQrev + dWrev = dQirev + dWirev. We have for an reversible process, dQrev = TdS and dWrev = -PdV. So; dE = TdS - PdV So this relation is for all changes (irreversible or reversible) since dS and dV are state functions. What doesn't make sense to me is the next part when...

Homework Statement a gas turbine is designed to produce 3000hp when using air at a maximum inlet temperature of 650k and assuming a heat loss of 70 kj/s. if the exhaust temperature is desired to be no greater than 200 degrees celsius, determine the mass flow rate of air required. Homework...

The following comes from Landau's Statistical Physics, chapter 32. Using a Hamiltonian \hat{H} = \hat{H}_0 + \hat{V} we get the following expression for the energy levels of a perturbed system, up to second order: E_n = E_0^{(0)} + V_{nn} + \sideset{}{'}{\sum}_m \frac{\lvert...

In thermodynamic perturbation theory (chapter 32 in Landau's Statistical Physics) for the Gibbs (= canonical) distribution, we have E = E_0 + V, where V is the perturbation of our energy. When we want to calculate the free energy, we have: e^{-F/T} = \int e^{-(E+V)/T} \mathrm{d}\Gamma We can...

I am working through a paper in which the chemical diffusion coefficient is related to the self-diffusion (or tracer) through the following derivation, on which I am a little hung up. AB2 metal. Overall diffusion D= XADB+XBDA meaning the chemical diffusion of B is...

I have read that every body possesses some energy of vibration due to the thermodynamic character and it is equal to 1/2 kT. Does this mean that we can detect the vibrations of bodies? Or ,as it is, does it ultimately end up as heat? Regards, Boltzmann2012

If we add a small amount of heat δq to a liquid at its boiling point Tb, it could either increase its temperature a small amount dT = δq/Cv, or suffer a phase change into vapor. Experimentally, we see that liquids remain at Tb until the phase change is complete, and only then continue...

EDIT: Turns out, the solution to my question is related to the determinant of a positive definite quadratic form. This is more or less straight from Landau's Statistical Physics Part 1 (3rd edition), Chapter 21. I don't understand how the inequality/condition (the last equation in this post)...

I don't have the intuitive picture of thermodynamic 2nd law, in terms of statistical mechanics. That is, why should the number of microstates be maximized in equilibrium? Anyone gives an intuitive explanation? Thanks a lot.

Homework Statement Plot cp as a function of temperature for O2? How does this compare with the cp expected for a diatomic ideal gas. Add this constant value to your plot. At what temperatures does the real value of cp approach that expected for a diatomic ideal gas. Homework Equations...

hi, I'm simulating a system of molecules (water) and in order to pass through a barrier they have to overcome an energy barrier of 4kT. What is the probability of a water molecule passing the barrier or perhaps what is the average energy of a water molecule in my system? I know it's 1/2 *kT...

Homework Statement http://i.imgur.com/2WKCR.jpg Homework Equations Potentially: L(final) = L[1 + tau/(YA) + alpha(T - To)] The Attempt at a Solution Frankly I have no idea where to begin.

dU = TdS - P dV Is in my book derived by viewing a proces of changing volume and energy in two separate steps. First you add energy with volume fixed, then change the volume. I'm just not sure that I understand why, you are allowed to do this. I know the changes are infinitesimal but why is...

Homework Statement Carpet steamer marketed for Greenland. Add up to 2 kg of snow or ice (no colder than -10°C) that will be converted to steam within 5 minutes. How powerful would the steamer need to be to make this claim? Know that 2108 J/kg K; Hf= 3.24*10^5 J/kg; Cwater= 4184 J/kg K; Hv =...

Homework Statement a) what is the density of dry air when the surface pressure is 1010hPa and the temperature is 27°C. b) what is the internal energy of 1kg of dry air under these conditions? Homework Equations P=p*R*T where P is pressure and p is density. The Attempt at a...

What the relationship between catalyst and thermodynamic. In activation energy as we know, it reduces the activation energy and what about thermodynamic way?

How are both statistical and thermodynamic defintion of entropy equivalent? THe statistical definition i.e. S = k ln ω amkes sense to me. It is the number of mcirostates an atom/moelcule can take over but how is the thermodynamic definition i.e. ΔS = q/T equivalent to it...

In thermodynamical equilibrium what would be the proportion of hydrogen to helium-4? According to the proton-proton chain branch I it would seem that the equilibrium would be 75% H-25% He-4? is this correct? (This is of course an unrealistic scenario).

Homework Statement Water is the working fluid in a Rankine cycle. Superheated vapor enters the turbine at 10 MPa, 480 °C condenser pressure = 6 kPa ηturbine = 80% ηpump = 70% determine a.) Qdot of the steam generator. b.) ηth c.) Qdot from the condenser to the cooling water. Homework...

Homework Statement [/B]A bullet traveling at 100 m/s strikes the wall inelastically. It is observed that the bullet's temperature rises by 10 Kelvin due to the collision. Find the specific heat capacity of the bullet if all of the bullet's energy goes into heat. Homework Equations ΔQ=mcΔT...

Homework Statement The mixing tank shown here initially contains 50 kg of water at 25°C. Suddenly the two valves and the single outlet valve are opened so that two water streams, each with a flow rate of 5 kg/min, flow into the tank, and a single exit stream with a flow rate of 10 kg/min...

Homework Statement See attachment ecxample001. Homework Equations See attachment D11. The Attempt at a Solution In the first equation (Cp/R = a+bT+cT^2...etc.), Cp/R is the constant pressure specific heat. The general formula for enthalpy change is h2-h1 = integral[Cp]dT, so does...

A heat Engine receives 6 kg/h gasoline which has a calorific value of 42000 kj/kg. If heat rejected from the engine is 40 kw, calculate a- the power done by the engine b- the engine effiecincy -this wt i got today in my exam and unfortuntely i didnt study it well but i did the following ...

For a thermodynamic process, what equations would be used to find the change in Gibbs and Helmholtz free energy when: a.)The process is adiabatic b.)The process is isothermic c.)The process is at constant volume d.)The process is at constant pressure I know ΔG=ΔH-TΔS and ΔA=ΔU-TΔS but do...

Homework Statement cp=cv+TV?^2/? Homework Equations cp=T/N(\partialS/\partialT)p The Attempt at a Solution I have the equation, just not sure how to apply it? Any help would be appreciated

Can someone please help me answer this question and explain the concepts/solution step by step: Prof. W.H Bogus claims that he has prepared a powerful new catalyst that makes it possible to synthesize NH3 with a 70% yield in a reactor operating 500K and 2 atm pressure and having a feed...

Homework Statement The figure shows a thermodynamic process followed by 130 mg of helium. How much work is done on the gas during each of the three segments? p_1 = 1.08 atm, p_2 = 5.41 atm, p_3=1.08 atm T_1=133 C, T_2=T_3=1760 C V_1=V_2=1000 cm^3, V_3=5000 cm^3 These are answers...

Hi everyone, I'm learning equilibrium thermodynamics on my own. I'm wondering how is the Kp(equilibrium constants) in the JANAF tables defined? Which reaction formula does it refer to? Thanks in advance.

I was reading an article about phase transition, i read about thermodynamic process such as Adiabatic process - a process with no heat transfer into or out of the system. Isochoric process - a process with no change in volume, in which case the system does no work. Isobaric process - a...

Homework Statement A mole of ideal gas with a temperature T1=300K is expanded isobarically until its volume is tripled .Then the gas gets colder isochorically until we reach the temperature we had in the beginning 300 K.Find the work of the gas. Hint : We have a thermodynamic cycle . Homework...

Homework Statement I have a problem which I will attach a picture of, regarding a system composing of a heat recovery steam generator and a turbine. I have to work out the power output of the turbine, which I think I will be fine with. What I would like to know is, how does the combustion...

Homework Statement The question is as following: One litre of an ideal gas, initially at atmospheric pressure, is held at a constant temperature of 300 K (by maintaining good thermal contact with a thermal reservoir held at this temperature). The volume is decreased until the pressure doubles...

Hiya guys, I've just started a project, of which the aim is to develop a thermodynamic property database for hydrcarbon fuels. I've been asked to start by reading up on the maxwell relationships and clapeyron equation etc. so hopefully this will give you an idea of what I am trying to...

Homework Statement The problem is as following: Homework Equations \Delta E = \Delta Q-\Delta W The Attempt at a Solution Now I know that if work is done by the system then work sign is negative and that if volume remains unchanged then no work is done. Am I right to say that Internal...

I'm struggling to derive some thermodynamic equations from this http://my.safaribooksonline.com/book/chemical-engineering/9780132441902/thermodynamic-properties-from-volumetric-data/ch03lev1sec1" : Homework Statement I'm trying to derive all the equations from 3.8 to 3.14 for Pressure...

I have the answer to this question but I'm finding it hard making sense of it... Q5) Dervive a relationship relating Cp-Cv to the isothermal compressibility (∂p/∂V)T and the coefficient of thermal expansion (∂V/∂T)p. Hint: consider the intensive entropy S as a function of T and V. So I've...

In an isobaric expansion process, the pressure of the gas is kept constant. Because of the increase in volume the constant pressure can only be archived by increasing temperature. Then I want to ask is the pressure of the gas necessarily equal to the external pressure throughout the whole...

1. Statement of the Problem One mole of a monatomic ideal gas is taken through the reversible cycle shown. Process bc is an adiabatic expansion, with P_b = 10.0 atm and V_b = 1.00E-3 m^3. Find a) the energy added to the gas as heat, b) the energy leaving the gas as heat, c) the net work done by...

Homework Statement Show that the work done by a reversible function from P1V1 to P2V2 is W = (P1V1 -P2V2)/ (x - 1) using the relation PVx = C where X and C are constants Homework Equations dW = PdV The Attempt at a Solution I'm going to have to update this more when i get...

Homework Statement Consider the fundamental equation S = AUnVmNr where A is a positive constant. Evaluate the permissible values of the three constants n, m, and r if the fundamental equation is to satisfy the thermodynamic postulates and if, in addition, we wish to have P increase with U/V...

Hi, before I start this is not coursework or any work attached to my degree but part of an internship at a neutron research facility at a level appropriate for Masters students and higer, so I felt it necessary to post it here rather than the homework section (sorry if I'm mistaken). I've been...

After a bit of calculation, I came up with the following quantity for the bit-entropy of a thermodynamic system. We have the following assumptions: 1. System at thermal equilibrium. 2. Ideal gas. 3. Monatomic gas (i.e. no internal degrees of freedom for particles). 4. All particles have equal...

Homework Statement I'm probably over thinking this question. An ideal gas is placed in a thin walled aluminum cylinder and slowly compressed to 25% of its original volume. The process is best described as adiabatic, isothermal, isochoric, or isobaric? Homework Equations none The...