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  1. apetri

    Real or ideal cp/cv for orifice sizing

    std. API formulation for PSV has been derived with ideal cp/cv , but for a blowdown design you can calculate the critical flow based on real density , cp/cv (for example from a EOS), note that there are models (for example HEM) suitable to calculate critical flow also for two-phase (vapor +...
  2. apetri

    Dew point for RNG

    for std. hydrocarbon mixtures EOS models are usually accurate within 1 .. 3 C , and with water one can adjust KIJ , there are good tools to calculate dew points, phase diagrams, regress KIJ etc. see for example https://www.prode.com/docs/pppman.pdf a point to discuss with yur client (to...
  3. apetri

    Excel Peng Robinson Vapor Liquid Ratio

    in Excel, Python etc. you can easily obtain fugacities, vapor/liquid fraction, mass and volume flows and many other properties with an add-in library, see https://www.prode.com/en/ppp.htm it includes many thermodynamic models suitable for LNG including Peng-Robinson, GERG 2008 etc. and a...
  4. apetri

    Body Bowl choking

    a chocked flow condition at PSV discharge should not be considered a problem except for additional vibrations and noise, reading your posts it seems that you are more concerned about the warnings and results produced by your simulator, I am not familiar with Aspen, with a different software...
  5. apetri

    Using Peng Robinson EOS

    Hi valves4life, with proposed procedures you solve molar volume (liquid and vapor phase) *NOT* the bulk modulus which is a derivative bulk modulus = -V dP/dV in the same way, if you wish to calculate the speed of sound you need additional derivatives and, for two phase conditions, the...
  6. apetri

    Life Cycle Cost & Optimum Compression ratio Per Stage of Centrifugal Compressor Package

    you may wish to contact a vendor to obtain accurate values, while there are books and papers discusing these topics (with different details, to mention two, Centrifugal Compressors: A Basic Guide or Compressor Performance: Aerodynamics for the User) there are several aspects to consider, for...
  7. apetri

    API 520 D.2.2 (Sub-cooled liquid)

    the paper "A generalized correlation for one-component Homogeneus Equilibrium flashing choked flow" by Leung 1986, introduces the Omega method, the API version adopts a 2 points evaluation but still it remains a simplified model with the limits of HEM (vapor and liquid at equilibria, traveling...
  8. apetri

    separation process

    kindly post on one group only, simulators can include many models, the operating manual can help with selection or you can consult books as Thermodynamic models for industrial applications etc. NRTL can be Ok for low pressures or you can, for example, select some EOS with complex mixing rules...
  9. apetri

    VLE Data in Aspen Plus (BIPs Regression)

    Iomcube, if you mean the possibility to transfer the calculated values from Prode (or another simulator) to Aspen, I agree that it could be not easy, many models in Prode and Aspen adopt different parameters and formulations, for example the extended versions of Peng Robinson in Prode Properties...
  10. apetri

    Application of Lee-Kesler EoS Mixing Rules

    probably, for hydrocarbons properties, the first accurate model was the AGA8-DC92 equation of state of Starling and Savidge (1992), limited to gas phase, at present (for hydrocarbons) the internationally accepted standards are the GERG 2008 (Europe) and the equivalent AGA 2017 (USA), there are...
  11. apetri

    Application of Lee-Kesler EoS Mixing Rules

    Sirius, are you a student ? You can find a good discussion about the different methods for estimating the critical properties of mixtures in The Properties of Gases and Liquids (Poling, Prausnitz, Connel) which I recommend, as general rule there could be large differences comparing...
  12. apetri

    VLE Data in Aspen Plus (BIPs Regression)

    it is not difficult to regress VLE (as well as LLE and SLE data) sets at different temperatures and pressures, supposing you have access to DDB database or a similar source you obtain X,Y values at different T,P see herebelow an example for Methanol-Water (free DDB data) you enter these...
  13. apetri

    Application of Lee-Kesler EoS Mixing Rules

    Sirius, in addition to pmover notes and comments, Lee-Kesler is a old and well documented method, you can find application examples in many books (my copy of Thermophysical Properties of Fluids includes the FORTRAN codes as in other books...), note that Kay's rule works well for rather similar...
  14. apetri

    Aspen Simulation Workbook; How Does It Capture Aspen Plus Or Hysys Variable String Automatically

    yes, I use Prode Properties library (on Windows and Linux), anyway there are other products (both commercial an free) with different levels of features and technical support, it depends from your needs, if you need to simulate plants with a large number of units probably a process simulator...
  15. apetri

    Effect of Type of Hydrates on Inhibiton consumption

    for many natural gas mixtures, both hydrate structures I and II can form, (as simple hydrates, C1, C2, CO2, H2S form structure I while N2, C3, NC4 form structure II etc.), as general rule, given a temperature, structures II can form at lower pressure than I , the presence of thermodynamic...
  16. apetri

    Aspen Simulation Workbook; How Does It Capture Aspen Plus Or Hysys Variable String Automatically

    if you connect via COM or equivalent mechanisms you may be able to create some script to, at each optimization step, transfer input data and get calculated values, however, in general, when connecting Python with external applications running as separate processes, this solution is not...
  17. apetri

    Sensible heat in Fire relief calculations

    take care that in some cases (for example for wellhead separators with design pressure about or above critical pressure of mixture) sensible heat must be taken in accout when solving the mass & heat balance during dynamic simulation (see my previous post), anyway this is not a problem for the...
  18. apetri

    Sensible heat in Fire relief calculations

    I have not Aspen, I use instead Prode but I suppose the methods are equivalent, in dynamic simulation (with Aspen, Prode, Vmg , Simsci or another software) at each step you solve mass & heat balance including as input the heat from fire and (as output) the discharging flow, this procedure allows...
  19. apetri

    Bottle Headspace Pressure

    if you know composition and initial condition then you can solve a constant volume (the volume of the bottle) flash operation at specified temperature to get the final pressure, I do not know how much accurate a extended EOS or a Helmholtz based model can be for your CO2 mixture (you should...
  20. apetri

    dynamic simulation of petroleum loading and its emission

    if you know, as you should if you wish to solve this problem, the initial compositions, volumes and flows, the standard procedure is to recalculate mass & energy balance (including phase equilibria) at regular intervals from T1 (initial) to T2 (final), you can solve these problems with a...

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