alpyurtsever

I have tried to do that for part a of the question, but I have failed. I found something different, and I think it is because I calculate the heat given to all system, so it is greater than the heat given to part of gas which is still inside the volume A. I will ask it to course assistant, thanks anyway. If I will fail to understand it, I will repost here a message

I will work on it and send it tomorrow again than. Thanks

So you suggest me to think that the tank is connected to an evacuated tank, and take the system boundries as the whole volume of two tanks? So there wouldn't be a mass flow out of the system, but I will have work term instead which is easier to compute?

I am posting my solution as a whole with part a and b. I know and understand these concepts but how can I use them? I have pointed where I am unable to continue solution in my answer sheet.

I don't know what turbo expander is? Is it a turbine, a compressor or something different? But I understand that I can use the state variables to solve the question. Do you mean it? For example for the piston case, the initial and final pressures are the same. If I can find one more same state variable, than all the others will be same.? Evacuated chamber can be a good approach, system can be selected as the all volume, it can be easier. But I didn't understand it totally I think. Maybe I have to research more. Is it about only the first Law of thermodynamics, will I use the entropy balance equation or, is it only about the conservation of energy?

I have allready looked at the links I am very happy now. Thank you for all your answers. I think I can answer the question with a good accuracy now. Moreover, I am happy about understanding what entropy is, because it is a difficult concept to understand, and that was a big step in this way I had allready have an idea about the relation between one direction flow, and now I am also getting into the context of randomness.

We are using the tables for steam in general, but I think that wouldn't be a big problem if I use it for air too. Instructor would accept it. However we won't have the table for air in exams, so it would also be good if I learn how to integrate it. On the other side, I was thinking about taking the temperature of the air leaving the system as constant at (Ti+Tf)/2 . Is it a bad approximation? Or does it work? I didn't understand your third approach. How can I model it with another system. I will be happy if you can show me any example of it. Thank you

Hi, I need your help in my homework. My Instructor asked that question? Why there is not a work term in entropy balance equation? I have researched about it and I found that, entropy has not an exact physical meaning, however it is associated with disorder or randomness. In another point of view, entropy defines the energy which is unable to do work. however I am not sure that these definitions are enough. On the other hand, I think entropy is a mathematical derivation, which is done by a purpose of having a balance equation which does not involve a work term. They have originated it from the one directional flow of heat (from high temperature to low). Is it true? Thanks for your help

Hi, I need help in my Thermodynamics Homework. The question is that, A rectangular steel tank having an internal volume of 1 m3 contains air at 2.5MPa and 20°C. A relief valve is opened slightly allowing air to escape to the atmosphere. The valve is closed when the pressure in the tank reaches 350 kPa. a) Calculate the amount of heat that must be added so as to keep the tank contents at 20°Cthroughout the process. B) Calculate the final temperature if the process takes place adiabatically. -- I have done the a part, using the first law of thermodynamics. I have posted it. I also tried to solve b with the same analysis but it failed because the equation at the end does not have a real solution. I thought that the 2nd Law can be used also, but I couldn't solve it anyway, because it is an unsteady state system and I don't know entropy of the mass leaving the system. Can you help me?