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  1. djack77494

    Heat Exchanger Design

    Too big an issue for generalizations. It will depend on quantities (i.e. Ljungstrom might work for a "large" system but would be impractical for smaller systems), pressures and acceptable pressure losses, and other factors. In some situations S&T, plate, and Ljungstrom exchangers might all be...
  2. djack77494

    heat exchanger input output orientation

    I'd say that 99 times out of 100 you want the hot streams to enter the top and leave the bottom, and just the opposite with cold streams. Even if you're worried about vapor or gas being trapped in the exchanger, the vapor is likely to be generated during a heating process. Similarly any...
  3. djack77494

    Determine NPSHa of centrifugal pump

    It's nice to have a design that will work under any/all anticipated conditions. Still, it may be overly conservative to assume that you will operate a bubble point liquid pump at a level below the bottom level instrument tap while the pump is at end of curve flowrate. Yet we often think that...
  4. djack77494

    Relief valve above/below demister

    I would also worry about the potential for high differential pressure across the demister that could lead to demister failure. Many demisters are designed for a relatively small dP across them. Should a PSV downstream of the demister pop, especially if you have full flow across the demister...
  5. djack77494

    NPSH for metering pumps

    You must use the second one since what you're trying to determine is the head available at the suction of the pump. Acceleration losses and suction line frictional losses impact that result.
  6. djack77494

    Slide rules live!

    I remember seeing an electronic calculator for the first time during my senior year in college. We called it an electronic slide rule, and it could barely do what a good slide rule did. A few years later, I got a metal hydraulic slide rule. One side for liquids and the other for gases. Boy...
  7. djack77494

    Design conditions of equipment

    MJC, Your statement, "The min specs include +10/-5 IWG pressure design; specific gravity minimum of 1.10" What a great idea. Will cost little or nothing for all but the largest of tanks and would save countless trouble and aggrevation. Wish this would be widely adopted.
  8. djack77494

    Sulfuric Acid Tank Overflow Liquid Trap

    Using air passing through a dessiciant vent dryer makes much more sense to me than piping over expensive nitrogen for vacuum relief. Carbon steel is just fine for this service, but ensure moisture is kept out. Your biggest challenge will be to find the compatable (with concentrated H2SO4 and...
  9. djack77494

    Who has the authority? Pump or Motor

    My opinion-You turn on the motor and the shaft spins up to speed. Fluid starts passing through the pump and things move pretty quickly to equilibrium. At this point, you can refer to your pump curve to figure out the power being consumed by the pump. The motor should have been purchased as...
  10. djack77494

    Excel 2007 Automatically changing formulas?!

    I wonder if this behaviour could be avoided if absolute addressing were used (i.e. use $A$1:$C$1)? My feelings on this "feature" are mixed, but I certainly can see occassions when it would be desirable.
  11. djack77494

    Gas thermal expansion and PSV

    tickle, Going back to your original post, I think it very unlikely (though not impossible) that ambient heating would cause a 25C gas to heat to 65C. Is the 65C just a maximum metal temperature due to solar radiation? Starting at 9000 kPa[G] = 9100 kPa[A] such heating would cause the pressure...
  12. djack77494

    Heat Transfer

    Probably not, unless there's a lot of superheat. It's a far better practice to use saturated steam for heat transfer purposes such as this. Almost all of your heat is latent heat.
  13. djack77494

    Flame Arrestors

    Stone, Based on your descriptions, it appears unlikely an explosive atmosphere could ever develop within your tank. If an adequate hazard analysis considers your situation, it should be possible to identify whether or not this is true. If the atmosphere inside the tank can never burn, then the...
  14. djack77494

    Heat transfer from buried pipeline

    Ideally, you'd have access to data from a similar situation and be able to use it to develop an estimate. You should be careful about generalizations in this situation. heat transfer to the soil is strongly impacted by factors such as soil moisture which may vary significantly over short...
  15. djack77494

    heat transfer through pipe

    Danette, Don't be discouraged. The hydraulics & heat transfer are pretty much independent of one another (I think). I'm having some trouble visualizing your total situation. You say your steam comes from a steam trap(s). That confuses me since you get condensate and not steam from a properly...
  16. djack77494

    heat transfer through pipe

    If you have access to simulation software, such as Hysys, ProII, or ASPEN, you may set up a simulation that will simultaneously solve the heat transfer and hydraulic losses portions of this problem. Other approaches will probably be quite a bit more work but can still be successful.
  17. djack77494

    Electrolysis for rust removal - The electrolyte solution question

    I'm not sure of why but can postulate that sodium carbonate lacks the hydrogen containing "bi-" ion and is therefore more alkaline. This may be a factor.
  18. djack77494

    hysys vs aspen one

    Hysys, ProII, and Aspen all have strengths and weaknesses. I am not technical enough to be able to provide a good analysis of the details.To the best of my knowledge, Aspen is widely used for chemicals, electrolytes, and solids. ProII seems to be the simulator of choice for refinery...
  19. djack77494

    Piping Estimation Software

    Please be more specific. Liquid, vapor, slurry. Laminar or turbulent. In plant? Pipeline? Network? Hydraulic calcs or costs or more?
  20. djack77494

    MAWP and MAOP

    I think that one very clear graphic way of thinking of the MAWP is that this is the pressure (at design temperature) above which the vessel may fail. Yes, I know we have our various overdesign factors and allowances, etc., but the vessel is built to be capable of withstanding the MAWP and not...

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