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  1. SilverRule

    Fanno Flow: I just don't get it

    Mannnn that gets me every time!! [banghead] haha. Thank you so much! I appreciate it. [thanks2]
  2. SilverRule

    Fanno Flow: I just don't get it

    Then I guess the main confusion is my second question which it doesn't look like you touched. That one completely flips my understanding upside down.
  3. SilverRule

    Fanno Flow: I just don't get it

    Hi guys, I just don't seem to get this topic fundamentally and also how to actually apply it. Just focusing on compressible flow by the way. Wikipedia starts by saying "Fanno flow is the adiabatic flow through a constant area duct where the effect of friction is considered." Basically, I...
  4. SilverRule

    Extremely basic question about compressible flow

    "For an ideal gas, the dU term will change due to a change in temperature of the gas." I'm not saying you're saying. But the question is how come the wiki page says that there's no change in temperature for an ideal gas through an expansion (see the screenshot I posted in my previous post)?
  5. SilverRule

    Extremely basic question about compressible flow

    The PdV work we're talking about here is strictly expansion work, not flow work. So could it be that work only needs to be done to expand only in circumstances where there's attractive forces whereas ideal gas has no attractive that are needed to overcome (in a case where it's only a fluid...
  6. SilverRule

    Extremely basic question about compressible flow

    Yep agree that dPV = dU for isenthalpic ideal gas expansion. None of the quantities change. Even though there is an expansion. Is your question that how can I say there is no PV work being done at the same time saying there's an expansion?
  7. SilverRule

    Extremely basic question about compressible flow

    Yes, one of the fundamental aspects of the Joule Thomson expansion is that it's an irreversible expansion and expansion through the throttle is the most irreversible situation because it happens the fastest (in one step if you will). I mean in fact, all real processes are irreversible and this...
  8. SilverRule

    Extremely basic question about compressible flow

    I'm slightly out of my element here as my thermo was always weak :( haha I think we're conflating two different types of work but unfortunately they're both called PV work which is confusing. Though these might be related in some way I don't well understand. You've been talking about flow work...
  9. SilverRule

    Extremely basic question about compressible flow

    Hey, thanks for the input. I don't believe V has to necessarily be an intensive property here. It is in h=u+Pv (small case, intensive) which seems to be just as valid/applicable as H=U+PV (capital case, extensive) where it is an extensive property. In the wiki link here, they show it in...
  10. SilverRule

    Extremely basic question about compressible flow

    Hey guys, I think I may have figured out the answer to my own question (possibly) if anyone is interested.. As I expected, I think it's confusion arising from semantics.. I think the PV quantity in the enthalpy equation H=U+PV has a slightly different meaning than the PV in PVk=constant...
  11. SilverRule

    Extremely basic question about compressible flow

    Anyone? [sad]
  12. SilverRule

    Extremely basic question about compressible flow

    Hey guys, Has anyone been able to have a chance to digest my last post? SR
  13. SilverRule

    Extremely basic question about compressible flow

    First of all, thank you for the response. There's a few separate things that need to be parsed out here... I'll first lay out all the expansion scenarios. I've got this from a wide mix of sources: Joule-Thomson (JT) expansion effect is isenthalpic, so H=U+PV must be constant. U consists of...
  14. SilverRule

    Extremely basic question about compressible flow

    Can anyone tell me if my question makes sense please? I'm not sure if the question is incomprehensible or if you guys aren't sure of the answer either. Maybe this thread has gotten too deep and messy and maybe I should just make a new clean independent thread with the question? Thank you!
  15. SilverRule

    Extremely basic question about compressible flow

    If anyone would like, let me just restate the question at hand: I was studying the wikipedia page on Joule-Thomson expansion effect closely in detail, because as I understand it, that is essentially the fundamental expansion that we see in compressible flow, which we've been discussing in this...
  16. SilverRule

    Extremely basic question about compressible flow

    Yeah, that struck me too as interesting. I think it reaffirms the saying "You don't know what you don't know". Initially I thought it was rather straightforward but the more we got into it, new questions that I hadn't considered kept popping up. But the gentlemen here have done an awesome job...
  17. SilverRule

    Extremely basic question about compressible flow

    Sure I'm willing to assume they're trying to cover all cases. But the thing is, I don't even see where they cover the usual case of temp dropping AND PV decreasing anywhere. The only time they talk about PV decreasing is here: "Conversely, a decrease in PV means that work is done on the fluid...
  18. SilverRule

    Extremely basic question about compressible flow

    Well no, I'm not saying wiki got it wrong and needs fixing necessarily (unless you're saying that) ... I don't know if it's right or wrong, I'm just seeing a dissonance between what you and katmar have said (volume not increasing sufficiently enough to keep PV constant for adiabatic) and what...
  19. SilverRule

    Extremely basic question about compressible flow

    Yes, that diagram or even a worked example using simple numbers would illustrate that the value of PV (i.e. P multplied by V) would decrease for adiabatic process. The volume doesn't increase sufficiently enough to keep PV constant (like it does in isothermal case). So P2*V2 would be less than...
  20. SilverRule

    Extremely basic question about compressible flow

    Oh no.. I'm not asking this question -> "Since PV must be constant for isothermal flow, how is it that they're saying PV increases in adiabatic flow?" That would be definitely be an absurd question blatantly trying to compare apples to oranges. It's more like this -> "We recognize that PV =...

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