Thermodynamic Definition and 459 Threads

Homework Statement Suppose a room with 75 m3 of air also contains 80 kg of glycerol and the initial temperature in the morning is 16 °C. If 1.2 kWh of heat is added to the room between morning and afternoon, calculate the final temperature of the air in the room in the afternoon. Use 18 °C for...

Damn title character limits. I just had the weirdest thought while rearranging my computer's case fans. I put my hand in front of one of them and felt a light breeze of air, telling me it was working. This is due to the local cooling produced where the fan's airstream comes in contact with the...

It seems possible to extract energy from the ambient air without temperature gradients (or at least with very small local gradients that will always be available). Being curious about this, I checked out some other threads and did not really find the specific question. (I did find some...

Homework Statement Hot magma (1500 K) is flowing into the Earth at rates of 0.05 meters/year, 0.5 meters per years and 1 meter per year. Although more total volume of magma will retain a temperature at or above 1150 K at higher rates of flow for any given time (say, at 1000 years), a higher...

I'm sorry for bad english. I wonder what is the differences between reversible-isothermal-expansion and irreversible-isothermal-expansion. Is their entropy same?

if anyone could answer these questions it would be much appreciated Pump 3 Q1. A gas, with mass of 2.3 kg, undergoes a thermodynamic cycle which consists of the following processes, 1→2 Isobaric expansion, =2.3 bar , 1=4.1 m3 and 2=7.9 m3 2→3 Isothermal compression (=constant) where...

Homework Statement In Herbert Callen's text 'Thermodynamics and an introduction to thermostatistics', 2nd edition, Problem 1.10-1 on page 32 presents ten potential fundamental equations of thermo systems, labelled (a) - (j), and asks the reader to identify the five that are invalid because they...

Im working on a project for fun using a peltier cooler. A tec1-12706. If i am operating the peltier at 9v, 6.4 amps of current and dt =45ºC (from datasheet) and bring its cold side in contact with a body at 33ºC for 10 seconds. Keeping hot side at 27ºC(cold side =-18) using sink, what will be...

one gram molecule of monoatomic gas is taken at s.t.p. keeping its volume constant,its temperature is raised by 1k. one gram molecule of the gas is added isothermally to this.the mixture is now cooled by 1k at constant volume to return to s.t.p. if [c][/v] be gram molecular specific heat of gas...

I don't understand how some terms are derived. How did the last term of 3-47 originate? How did 3-49 get so many terms from just one term in 3-41? Why integrate from V to infinite? That is not intuitive. Thas a functions are unusual because the absolute values of U,H,S cannot be computed...

Homework Statement Two moles of an ideal mono atomic gas (C2=12. 55 JK-1mol-1) expands irreversibly and adiabatically from an initial pressure of 10 atm against a constant external pressure of 1 atm until the temperature drops from the initial value of 325 K to a final temperature of 275 K...

Homework Statement My question is how can one derive U(S(V,T),V) from the relation U(S,V,N).This is the beginning of a given solution which is not explained in more detail. Homework EquationsThe Attempt at a Solution I can understand U(S,V,N) as dU=TdS-pdV+μdN but not the transition...

Estimate the kilowatt pump you would need to pump 450 L/min of liquid water at 20c through a rise in elevation of 100m. Assume the water is pumped adiabatically and with negligible changes changes in temperature and kinetic energy. answer given to us is -7.35kw.. Question.. what formula should...

This is not a homework question, but more of a information seeking question. I'm currently enrolled in Fundamentals of Thermodynamics where we studied many different cycles (Carnot, Rankine, Otto, Brayton, etc.) and their respective components (compressors, turbines, heat exchangers, pumps...

Homework Statement Hi, I'm a new user and got this problem. Sorry to bother, but I couldn't find any relevant information from my Physics books.. The problem states: Build a heat engine using these processes: adiabatic, isothermal, isochoric and isothermal. The work-cycle of the engine must...

The thermodynamic efficiency ##\eta## is calculated by ##\eta= \frac{W_{out}}{Q_{in}}## Using the first law of thermodynamics we usually say that ##W_{out}## is ##Q_c+Q_h##, where ##Q_c## is the heat dissipated into a cold reservoir, and ##Q_h## is the heat absorbed by the system because of a...

Homework Statement For a single molecule, derive the internal energy U = 3/2kBT In terms of the partition function Z, F = -kBTlnZ Where Z = V(aT)3/2 Homework Equations Thermodynamic identity: δF = -SδT - pδV p = kBT/V S = kB[ln(Z) + 3/2]The Attempt at a Solution U = F + TS δU = δF +...

In deriving thermodynamic temperature scale, it uses the concept that heat transfer between two reservoirs is the function of the reservoirs' temperatures. i.e. Q1/Q2=Φ(T1,T2). And then further express that Φ(T1,T2)=ψ(T1)/ψ(T2). I have two questions, 1. Is it a hidden assumption that the...

Homework Statement What is the difference between the absolute thermodynamic temperature scale and the practical temperature scale: ITS-90? Homework EquationsThe Attempt at a Solution

Homework Statement The stirling approximation, J! = √JJ+1/2e-J, is very handy when dealing with numbers larger than about 100. consider the following ratio: the number of ways N particles can be evenly divided between two halves of a room to the number of ways they can be divided with 60% on...

Homework Statement I have been given a description of a thermodynamic cycle that looks like this. I have two polytropic processes (n1=1.2, n2=1.9), and one isochoric. The known data are: p1 = 1 bar T1 = 15 °C p2 = 15 bar Homework Equations p v^(1.2) = 0.7958 p v^(1.9) = 0.69657 The Attempt...

Hello everybody, I am a new member and do not know what is the best way to asking question. in "Statical physics of particle , m.kardar" . how he derived eq1.6 ? he said that we can eliminate "C" from eq1.4, but how? http://libgen.org/book/index.php?md5=BC07A3BDB70689E0E612DED12C96CC78 the book...

I am trying to understand the (possible) couplings between scalar chemical reaction phenomena and vectorial phenomena such as heat conduction and mass diffusion. It is argued in the literature that I have read that the usual assumption of cross coefficients for scalar+vectorial phenomena only...

Homework Statement Hi I am new to Physics Forums and desperately need some help! This is my first class back since undergrad and my math skills have gotten a little rusty. I think that's where I am failing. Okay here goes: http://tinypic.com/r/2zqf04k/8 There is a 4 subsystem...

What are the purposes of defining the Thermodynamic functions such as H (enthalpy), G (Gibbs function), A (Helmholtz function) in Thermodynamics. I just know the expressions for this functions but unable to understand the physical significance of these functions and also haven't understand what...

Hi I am using relap to study a blowdown transient. If I let it run it with actual heat fluxes, the program terminates with error message saying thermodynamic property error with maximum time step. Reducing the time step delays the onset of the error by a fraction of a second. Runs much longer...

I am trying to understand why I can specify the specific volume v of a fluid element as a function of the equilibrium pressure, p, and the equilibrium entropy, s. This is for example done in this article http://www.sno.phy.queensu.ca/sno/str/SNO-STR-95-051.pdf , on this website...

Hi there, I have been thinking about attempting to quantify the statement that: "Gasification is more efficient thermodynamically than direct combustion of the fuel source as the gas can be combusted at higher temperatures, resulting in higher thermodynamic efficiencies as defined by...

We know that for constant pressure thermodynamic processes which only expansion work is possible, dH=dQp. My question is, is it necessary that both work W and Qv be reversible to arrive this relation? What if the heat transfer is irreversible? Similar question for dU=dQv, does the heat...

Hi, I'm looking at a derivation of the thermodynamics of black-body radiation. My question is in regards to the math of the derivation. Using the first law of thermodynamics and considering an adiabatic expansion of the cavity, it can be stated that dU = -\frac{u}{3}dV Here small u...

We know that for constant pressure thermodynamic processes, dH=dqp. My question is, does it implies that only reversible work is possible in this processes so that dw=0 because dv is zero? In addition, does qv necessarily be reversible heat transfer in this case? What if the heat transfer is...

We Now From Information Theory That Entropy Of Functions Of A Random Variable X Is Less Than Or Equal To The Entropy Of X. Does It Break The Second Law Of Thermodynamic?

I recently came across the paper 'Relation between the psychological and thermodynamic arrows of time' (arXiv). Their argument makes sense to me, however their concept doesn't seem to address what 'now' is. If each person exists in an unchanging state in the block universe, and the flow of...

Homework Statement Find the equation of the thermodynamic process in which specific heat of the gas is given by C=\dfrac{R}{\gamma -1} + \alpha P The Attempt at a Solution I can write C=C_v + \alpha P But I don't know how to proceed ahead. What does C mean here? Is it specific heat...

hi guys , I am studying thermodynamic cycles in my thermodynamic course , I have a question about the power cycles like Rankine , in these systems v use superheated steam to produce work from turbine, so y there must be condenser to cool it first and then heat it , y can't v use turbine - boiler...

Homework Statement ''A rigid insulated container fitted with a paddle wheel contains 5lb of water, initially at 260F and a quality of 60%. The water is stirred until the temperature is 350F. For the water, determine the work.'' How do we know whether the state of the water at 350F is...

Dear Friends, I carried out an experiment of sudden release of oxygen (open nozzle) from an oxygen cylinder used for medical college and hospitals. I found that pressure drops quite rapidly and cylinder surface cools from outside such that water droplets accumulate on its surface. This...

I am trying to use thermodynamics manipulations in order to find \partialP/\partialV (at constant entropy) I tried replacing P by T(\partialS/\partialV)(at constant Energy) and then differentiated that by V but didn't help me. Do you have any idea where I can get around with this? Just throw in...

http://en.wikipedia.org/wiki/Critical_point_%28thermodynamics%29 Look here please. Why is the first and 2nd order derivatives of pressure with regards to volume equal zero at the critical point for an isotherm phase curve? Why/how is it possible to expand a fluid at its critical point...

Hello, I am trying to use some functions in MathCad given in my thermodynamics textbook to calculate thermodynamic properties. I attached the functions below. I try using them and then I get an error saying too many commas I just type in: MCPH(T1,T2;A,B,C,D)= of course with numerical...

So I have had related questions over the past month, but I would like to ask this question to clarify my understanding. In thermodynamics you work with certain potentials, which are a function of the thermodynamic variables, i.e.: U(S,T,V,N,P) Now for U one has the identity: dU=...

It seems to me that for some thermodynamic variables it makes sense to talk of systems in contact with different values of these variables. An example is temperature. We can the problem of two systems in contact with different temperatures. However, I am not sure if this is the case for all...

Hello, could someone please let me know if I have worked this problem out correctly, or if I need to try again? Thank you. Homework Statement A 40.0 g projectile is launched by the expansion of hot gas in an arrangement showing in Figure P12.4a (attached file). The cross-sectional area of...

Homework Statement In oppgave 1 a) I am supposed to show that the given equality is true (namely that the isoterm compressibility coefficient partial-differentiated with regards to temperature = isobar coefficient differentiated with regards to pressure multiplied by minus one)...

Homework Statement In the thermodynamic cycle as shown, a) What is the direction that the cycle is executed-clockwise or anticlockwise? b) What is the work done? Homework Equations First law of thermodynamics for a cycle E2-E1= Q-W= Tds-Pdv=0 The Attempt at a Solution a) I...

A "new" thermodynamic theory of life Interesting idea... https://www.simonsfoundation.org/quanta/20140122-a-new-physics-theory-of-life/ The peer-reviewed paper, published in AIP: Journal of Chemical Physics: Statistical physics of self-replication...

Homework Statement A solar hot water system is designed to supply 100% of the hot water demand of 0.6 m3/day when the isolation on the tilted collector is 22,000 kJ/m2 with a collector efficiency of 50%. The tap water temperature is 8ºC and the desired hot water temperature is 58ºC...

So I read somewhere that if we know u(s,v) i.e. internal energy as a function of entropy and specific volume, we can find all other thermodynamics quantities on earth, like temperature, pressure, Gibb's free energy from it. However, is this true if we have u as a function of just any two...

I know the formula q = mcT and that's the only formula I was taught before assigned these questions (in bold). 1. What mass of iron would be needed to have it increase by 6 degrees with 300J of heat. I am not sure what is meant by the increase of 6 degrees. How do you solve it without knowing...

Homework Statement Complete this table for H20: Homework Equations T, °C...P, kPa.....h, kJ/kg...x Phase...description 200 ............0.7 140.........1800 ......95.........0.0 80....500 ......800.....3162.2I just need help getting started, all I have is a packet full of tables and I don't...