What will be the flow direction?

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Discussion Overview

The discussion revolves around the flow direction of gas between two chambers under various conditions, focusing on thermal equilibrium, pressure, and density variations. Participants explore the implications of the ideal gas law and thermodynamic principles in different cases, including scenarios with and without heat flow.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that in case 2, there would be no flow, while others argue that case 3 indicates flow from chamber 1 to chamber 2 based on fluid mechanics principles.
  • There is uncertainty regarding whether heat can flow between the chambers, with some stating it is allowed and others questioning the implications of thermal equilibrium.
  • Participants discuss the relationship between temperature and pressure, raising questions about how changes in temperature (T1) affect pressure (P1) and the overall system behavior.
  • Several participants propose that flow direction is influenced by density variations due to temperature differences, suggesting that flow would occur from higher density to lower density regions.
  • Some participants emphasize the need to consider the number of moles of gas in each chamber before and after the valve is opened, questioning how this affects equilibrium and flow direction.
  • There are repeated inquiries about the application of the ideal gas law and the implications of the first law of thermodynamics on the system's internal energy and final states.
  • Some participants express confusion about the practical aspects of the scenarios presented, seeking clarification on the assumptions made in the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the flow direction in case 2, with competing views on whether flow occurs despite the number of moles present. The discussion remains unresolved regarding the implications of thermal equilibrium and the conditions under which flow occurs.

Contextual Notes

Limitations include assumptions about thermal equilibrium, the nature of heat flow between chambers, and the dependence on specific numerical values for pressure, temperature, and density that are not provided.

Ravi Singh choudhary
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I guess there would be no flow in case 2; case 3 seems easy to me applying fluid mechanics principle; flow will be 1 to 2. But I doubt case 1; it is not in thermal equilibrium ? Pls help
 
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Can heat flow between the two chambers, or are the insulated from one another?
 
You may assume the system will tend to go to equilibrium. What does that mean for T1 and T2 ? If they don't stay the same, then what does the change in T1 mean for P1 ?
 
Yeah, heat flow is allowed between chambers;
What you are seeing is just a valve between two chambers.
 
BvU said:
You may assume the system will tend to go to equilibrium. What does that mean for T1 and T2 ? If they don't stay the same, then what does the change in T1 mean for P1 ?

It doesn't seem practical to me also. So pls answer one that you want to acknowledge.
 
Ravi Singh choudhary said:
It doesn't seem practical to me also. So pls answer one that you want to acknowledge.
Could you replhrase ? I don't understand what you are trying to tell me. Basically I don't answer: I help answering by asking questions. About case 1.
 
BvU said:
Could you replhrase ? I don't understand what you are trying to tell me. Basically I don't answer: I help answering by asking questions. About case 1.

Pressure is equal before; but temperature T1 is more----> They would try to attain the thermal equilibrium. When valve is being opened; I don't know what would happen; simply because I am not able to think; because I don't have numerical values how can I compare the density (say). I could say if there is density variation due to temperature difference simply flow will be from higher density to lower density side.
 
You have the ideal gas law for guidance.
 
Ravi Singh choudhary said:
I could say if there is density variation due to temperature difference simply flow will be from higher density to lower density side.
Is it right approach?
 
  • #10
Check out ##p_1V_1 = n_1RT_1## in combination with ##p_2V_2 = n_2RT_2## in combination with ##p_1 = p_2##, ##V_1=V_2## and ##T_1 > T_2##. What about ##n_1'## and ##n_2'## after equilibrium is established ?
 
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  • #11
Why can't we apply simple fundamental principle that heat flows from higher temperature to lower temperature?
 
Last edited:
  • #12
We do apply that. But to answer the question what that means for the material flow we need a follow-up step.
 
  • #13
CASE 1: According to the ideal gas law, how many moles of gas are present in container 1 before the valve is open? How many moles of gas are present in container 2 before the valve is open? Does the total number of moles of gas in the two containers change after the valve is open? In the final equilibrium state, are the temperatures in the two containers (a) the same or (b) different? (If they are the same, then call that T). Does the overall system do any work on the surroundings? Does the overall system exchange any heat with the surroundings? From the first law of thermodynamics, what does that tell you about the change in internal energy of the overall system? From this, what is the final temperature? What is the final pressure? What are the final number of moles of gas present in container 1? How does that compare with the initial number of moles of gas present in container 1?
 
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  • #14
Better yet, if the final temperatures, pressures, and volumes are equal, what does that tell you about the final ratio of the number of moles of gas in each container?
 
  • #15
That means in all the cases; simply we have to find the ratio of moles of two chamber. Flow direction will be from higher to lower number of moles.
 
  • #16
Ravi Singh choudhary said:
That means in all the cases; simply we have to find the ratio of moles of two chamber. Flow direction will be from higher to lower number of moles.
Not in case 2. In case 2, there will be no flow even though there are more moles in chamber 2.
 
  • #17
Chestermiller said:
Not in case 2. In case 2, there will be no flow even though there are more moles in chamber 2.
I think more moles will in chamber 1 in case 2.
 
  • #18
Ravi Singh choudhary said:
I think more moles will in chamber 1 in case 2.
Sorry. I got it backwards.
 

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