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  1. rbcoulter

    gasoline vapor properties

    What is the situation? Are you sure this is essentially pure gasoline vapor? The vapor above liquid gasoline in an atmospheric storage will have a significant amount of air also. The ration of air / gasoline vapor depends on the vapor pressure of the gasoline which is also dependent on...
  2. rbcoulter

    Parallel flow in duct - general question

    Yes. It's similar to electrical circuits. Voltage drop is like pressure drop - they are measure from node to node. If the channels were different sizes then the flows in each channel would vary to make the pressure drop the same in each path (assuming they all share the same nodes)...
  3. rbcoulter

    would you discourage your child to take up engineering in college?

    My biggest complaint about engineering is that it hard to stay in one place and be successful. If one doesn't get with a major stable company early in their career, then moving frequently is nearly always the case. Event those that are with one company their entire career may be pressured to...
  4. rbcoulter

    Parallel flow in duct - general question

    Your flaw is that Pressure drop in parallel is not computed by reciprocal of reciprocal sum relationship. That is for the resistances the channels, not the pressure drop. The pressure drop is the value you calculated for each small channel.
  5. rbcoulter

    Perception of risk

    Sounds like it may be a very interesting book. Of course, risk is simply severity times frequency. Politics over-emphasizes severity and de-emphasizes frequency. How is it that we tolerate over 35,000 highway fatalities? There might be some justification for this. A high severity low...
  6. rbcoulter

    Ch. E. Reference Manual for PE exam - which one is best?

    Again. Your best reference manual is the FE handbook (yes it's good for the PE exam also) provided free of charge in PDF format at: http://www.ncees.org/exams/study_materials/fe_handbook/
  7. rbcoulter

    Ch. E. Reference Manual for PE exam - which one is best?

    Use the NCEES exam practice books at www.ncees.org. These are the people that make the exam.
  8. rbcoulter

    Problems calculating pump flow

    If you are constrained by the information available then there is no way to determine the flow rate. This is easy to see in that the data provided could apply to a significant range in size & style of pumps. The weight of the pump and inlet /outlet diameter do not help much at all. You could...
  9. rbcoulter

    Problems calculating pump flow

    Why not look at the pump curve?
  10. rbcoulter

    Good Engineering Practices

    Maybe one way to look at this is from a regulator's viewpoint. If you have an incident with an applicable process, the regulator/inspector will try to find faults in your program. They will definitely site you for not abiding by specific codes/regulations that are applicable. What if they...
  11. rbcoulter

    Micromanagement!

    Give that boss a fake project to work on. Or design a system with a bunch of bogus knobs and ask that boss how the knobs should be set. Listen intently to this boss and admire and complement all his/her suggestions and then go about doing it your way instead. Above all, find something for...
  12. rbcoulter

    Choked and sonic flow

    Yes. Only the inlet "stagnation" pressure changes with all the assumptions mentioned earlier. This is "P" in Milton's equation which assumes a zero approach velocity. It sounds like your trying to remove the constraint of zero approach velocity going from case #1 to case #2. In this way you...
  13. rbcoulter

    Choked and sonic flow

    Yes. But neither is finite for this model. If you try to get me to accept that then the model in invalidated and you can make your case.
  14. rbcoulter

    Choked and sonic flow

    Oh. So now I see your trick. The inlet area is considered very large compared to the throat in both cases. Trying to define a fixed inlet area does not work for this equation. May not sound realistic but it is my understanding that is the assumption behind the derivation of the equation...
  15. rbcoulter

    Choked and sonic flow

    Assume conditions as previous post: Case #1: 1. Po = Stagnation Pressure = Inlet Pressure (inlet nozzle area is very large compared to throat) 2. To = Inlet temperature 3. T* (throat temperature) = To*(2/(k+1)) 4. Throat velocity (choked) = c* = sqrt(kRT*/Mw) Case...
  16. rbcoulter

    Choked and sonic flow

    All my posts have been in reference to Milton's posting of the discharge equations above. Sorry if I didn't make myself clear. If one assumes the following: 1. Isentropic flow through a nozzle (before and after) 2. The same ideal gas (before and after) 3. Heat capacity ratio doesn't change...
  17. rbcoulter

    Choked and sonic flow

    Are not the stagflation and inlet temperatures essentially the same when there is near zero approach velocity (in the case of a large tank with a hole)? If you are arguing that this is never the case in real life then I see your point. However, must release models/equations assume these...
  18. rbcoulter

    Choked and sonic flow

    I am not convinced. I would be interested in reading the Mechanical Engineer's handbook version of the problem.
  19. rbcoulter

    Choked and sonic flow

    Latexman: Temperature at throat (T*) (choked flow, ideal gas, isentropic) is: T* = To*(2/(k+1)) ; To = inlet stagnation temperature Sonic Velocity is: c* = sqrt(kRT*/Mw) ; T* is only dependent on k and inlet temperature. So sonic velocity doesn't change. The above from Perry's 7th...
  20. rbcoulter

    Choked and sonic flow

    Sailoday28: OK. An ideal gas is flowing through an isentropic nozzle at choked conditions. We now increase the inlet pressure without changing the inlet temperature. Does the throat velocity increase? At choked conditions the pressure ratio (P/Po) does not change. Also, the temperature...

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