Intermediate Thermodynamics Questions & Answers  
Question by Student 201900041
Professor, for the question #6 Assignement 4, can we make the Steady State assumption ? So the system is independant regarding to the time? Thanks for your previous quick answer.
04.05.19
As much as possible try to set things up so that the system is at steady-state — this will simplify things. Thus, when solving a problem choose the reference frame of the control volume such that the properties don't vary in time anywhere within that volume.
Question by Student 201327106
Professor I have solved all problems needed to be solved my own. But when it comes to problems you did not give answer, I am not sure what I did is totally correct.
So can you give me answer of #4, #5 of Assign. 1, #7 of Assign. 2, and #4, #5 of Assign. 3?
Thank you.
04.22.19
These problems are easier than those I gave answers to. You should be able to get the right answer on your own. There are no answers when solving new engineering problems in industry: it's good to start practicing for these situations now.
Question by Student 201327106
Firstly, for non-ideal gas e.g.2 with the generated compressibility charts, you used below equations. $$P_{c}= \rho _{c}RT_{c}, \, {v_{c}}'=\frac{RT_{c}}{P_{c}}$$ But at table A-1, there is $Z_{c}$. Why didn't you use below equations? $$P_{c}= Z_{c}\rho _{c}RT_{c},\,{v_{c}}'=\frac{Z_{c}RT_{c}}{P_{c}}$$ $$\\$$ Secondly, why is there prime mark with ${v_{c}}'$? $$\\$$ Thank you and have a nice holiday!
05.05.19
But $v_c \neq v_c^\prime$: $$ v_c = \frac{Z_c R T_c}{P_c} $$ and $$ v_c^\prime \equiv \frac{R T_c}{P_c} $$
Question by Student 201427145
Professor, I have thought about Thermally Equilibrium that you had mentioned at last class. We can assume initially Diaphram X(closed system) divided in two Volume by membrane and each has Gas A, B. And then membrane has eliminated and Gas A and B mixed perfectly. Diaphram X, gas A, B have energy of $$E_{X}, E_{A}, E_{B}$$ each other. First, $$Define:\Omega(E)\equiv$$[Number of Microstate according to Energy]. If system has Energy(E), what we can see is macrostate but it is one of a lot of microstate case of probability distribution. Macrostate can be easily occured at E which makes Maximum number of Microstate. $$ \therefore\frac{d\Omega(E_{X})}{dE}=0 $$ Here Maximum Number of Microstate occurs at Energy of X, A and B. For the convenient, Let's focus on Energy of A. $$ \therefore\frac{d\Omega(E_{X})}{dE_{A}}=0 $$ Note: Closed system- $$ E_{X}=E_{A}+E_{B} \Rightarrow \Omega(E_{X})=\Omega(E_{A}+E_{B}) $$ State A and B is independent- $$ \Omega(E_{A}+E_{B})=\Omega(E_{A})\Omega(E_{B})\Rightarrow \Omega(E_{X})=\Omega(E_{A})\Omega(E_{B}) $$ $$\therefore \frac{d\Omega(E_{x})}{dE_{A}}=\frac{d\Omega(E_{A})\Omega(E_{B})}{dE_{A}}=\Omega(E_{A})\frac{d\Omega(E_{B})}{dE_{A}}+\Omega(E_{B})\frac{d\Omega(E_{A})}{dE_{A}}=\Omega(E_{A})\frac{d\Omega(E_{B})}{dE_{B}}\frac{dE_{B}}{dE_{A}}+\Omega(E_{B})\frac{d\Omega(E_{A})}{dE_{A}}=0 $$ $$ Note: E_{X}=E_{A}+E_{B}=const\Rightarrow dE_{A}+dE_{B}=0 \Rightarrow\frac{dE_{B}}{dE_{A}}=-1 $$ $$\therefore -\Omega(E_{A})\frac{d\Omega(E_{B})}{dE_{B}}+\Omega(E_{B})\frac{d\Omega(E_{A})}{dE_{A}}=0 $$ $$ \frac{1}{\Omega(E_{A})}\frac{d\Omega(E_{A})}{dE_{A}}=\frac{1}{\Omega(E_{B})}\frac{d\Omega(E_{B})}{dE_{B}} $$ $$Note: \frac{dln{\Omega(E)}}{d\Omega(E)}=\frac{1}{\Omega(E)} \Rightarrow\frac{d\Omega(E)}{\Omega(E)}=dln{\Omega(E)} $$ $$ \therefore\frac{dln{\Omega(E_{A})}}{d\Omega(E_{A})}=\frac{dln{\Omega(E_{B})}}{d\Omega(E_{B})} $$ $$Define: \frac{1}{k_{B}T}\equiv\frac{dln{\Omega(E)}}{d\Omega(E)} $$ where $$ k_{B}$$ is Boltzmann constant $$ \therefore\frac{dln{\Omega(E_{A})}}{d\Omega(E_{A})}=\frac{dln{\Omega(E_{B})}}{d\Omega(E_{B})}=\frac{1}{k_{B}T} $$ $$\therefore T_{A}=T_{B}=T-Answer $$
05.16.19
This is a good effort. It's a bit unclear whether $$ \therefore\frac{d\Omega(E_{X})}{dE_{A}}=0 $$ is correct. But it's on the right track.
Question by Student 201327112
Professor, I have a question on the question #3 (b) on the assignment #9. Before, I assumed that there are water condensation through the combustion process on the question #3 (a). But, I can't find the exact value of the temperature of water condensed in the combustion chamber. Is it right to assume the Hydrogen atoms are entirely react with Oxygen and then transformed to water liquid? If not so, How to regard the products of Hydrogen in the Methane after combustion? (In the question, you didn't give the percentage of products configured with Hydrogen atoms)
06.12.19
There is no water condensation here.
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