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Dr. Barber

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About Dr. Barber

  • Rank
    Project Manager

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  • Engineering Field
    Mechanical
  • License
    PE
  • Discipline
    Mechanical

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  1. Looks like in the new version 1.1, they fixed the efficiency of the Otto cycle and the COP of the gas refrigeration cycle.
  2. LOL WHAT?!?!?!?!?! OMG the mass flow rates in the two stages can never be the same. Energy conservation in the intercooler requires: m6h6 + m4h4 = m1h1 + m7h7. (assuming a well-insulated chamber) Now let m_highP = m1 = m4 and m_lowP = m6 = m7. Put these in the energy balance to obtain: m_lowP (h6 - h7) = m_highP (h1 - h4) thus the mass flow ratio is: m_lowP/m_highP = (h1-h4)/(h6-h7) Look now in the P-h diagram for the cycle to see that the ratio (h1-h4)/(h6-h7) is ALWAYS < 1 and can never be 1. I'm speechless.
  3. Yes. I have reported most of the things in this thread to them. Not this latest set of findings, but I will get around to it probably this weekend.
  4. Thanks. I hadn't noticed the "mu" -- good catch. Yeah, what a sh*t show. That first chart is useless. In their defense, they do provide a reference to where the chart came from. Maybe it's messed up in the original source and they just copied it. It shows, however, that nobody who is participating in the creation of this manual has used the dang chart.
  5. That's the kicker with this manual. They use lb, lbf and lbm. Sometimes by "lb" they mean "lbm" and sometimes they mean "lbf". I mean, this thing is just a real hoot.
  6. Ok, I welcome any clarification and pointing out what I'm doing wrong here. If I'm not making any dumb mistakes, then this is further proof that this handbook is an unmitigated disaster. Consider this simple question: What is the dynamic viscosity of SAE 50 oil at 50C? If we use the graph in page 10, we get... what do we get? I have no idea. is this 4.5? 45? 450? Note there is a 10^2 below the horizontal red line and another 10^2 above the red line. At first I thought the 10^2 below was a typo and should be just 10, but there is already a 10 further below. So, ¯\_(ツ)_/¯ Then I thought I could use the imperial units graph of page 9. Going in there at 122F (50C) I get 16 reyn, which is 1.1x10^8 mPa*s which is nowhere near anything close you could get from the SI chart. So, yeah, unless I'm doing something really wrong, this is REALLY screwed up.
  7. The unit conversion table in page 2 erroneously has the viscosity unit "reyn" as equal to 1 lb-ft/s^2 where it should be 1 lbf-ft/s^2.
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