RefProp-Connector for CHEMCAD Help

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This page explains how to use the RefProp-Connector for CHEMCAD.

REFPROP is an acronym for REFerence fluid PROPerties. This program, developed by the National Institute of Standards and Technology (NIST), calculates the thermodynamic and transport properties of industrially important fluids and their mixtures. REFPROPTM is based on the most accurate pure fluid and mixture models currently available. See the REFPROPTM website for a detailed list of data and features of REFPROPTM.

Summary

RefProp-Connector for CHEMCAD makes the REFPROPTM flash and property calculation routines accessible from within CHEMCAD for one named user.

RefProp-Connector is a DLL file for CHEMCAD, which communicates with REFPROPTM. It is loaded into CHEMCAD via CC-API Add-on Manager.

Then, select the calculation routines in the CHEMCAD Thermodynamic Settings.


Benefits of using REFPROPTM Calculations

The CHEMCAD models for equilibrium calculations (K-value Models) and enthalpy calculations (Enthalpy Models) are very generic and can be applied to almost any kind of components and mixtures. However, this flexibility is at the expense of accuracy.

Whenever highly accurate property calculations for pure components are required, the use of High Precision Equations of State (HPEoS) and REFPROPTM is a good choice.

Use Cases for the RefProp-Connector

Typical applications are the simulation of

  • throttling processes, e.g. safety relief processes,
  • all kind of super-critical processes, e.g. carbon capture and storage (CCS) processes, especially for the compression part,
  • all kind of Rankine Cycles, Refrigeration Cycles, and Heat Pump Systems, etc. Furthermore, novel functional substances for heating, ventilation, and air conditioning (HVAC) applications commonly are available first in REFPROPTM before they are added to the DIPPR database, which CHEMCAD uses.

Functionality

How RefProp-Connector for CHEMCAD works

RefProp-Connector for CHEMCAD makes the REFPROPTM flash and property calculation routines accessible from within CHEMCAD.

RefProp-Connector is a DLL file for CHEMCAD, which communicates with REFPROPTM. It is loaded into CHEMCAD via CC-API Add-on Manager.

It brings the REFPROPTM equilibrium (K-value), enthalpy, density and viscosity calculations for pure components into CHEMCAD.

Select these calculation routines in the CHEMCAD Thermodynamic Settings.

Steps to Install RefProp-Connector

With CHEMCAD and REFPROPTM installed, RefProp-Connector is installed in five steps (skip steps 2-4 if Add-on Manager is already installed):

  1. Purchase RefProp-Connector for CHEMCAD.
  2. Get the free CC-API Add-on Manager and install.
  3. Start Add-on Manager from within CHEMCAD (Go to Tools>CC-API>Add-on Manager) or from Windows.
  4. Log into Add-on Manager with your cc-api.com account.
  5. In Add-on Manager, find “RefProp-Connector for CHEMCAD” under the “Purchased” tab and install.

Steps to Use RefProp-Connector

How to use the REFPROPTM Flash Calculation

To use the REFPROP Flash Calculations select ADDK as K-value Model from the Thermodynamic Settings menu. This automatically selects ADDH as Enthalpy model in CHEMCAD.

How to use the REFPROPTM Property Calculation

To use the REFPROPTM liquid density calculation select “usradd:ccapi_refprop_density” as liquid density mixing rule.

To use the REFPROPTM liquid viscosity calculation select “usradd:ccapi_refprop_viscosity” as liquid viscosity mixing rule.

How to add REFPROPTM components which are not in CHEMCAD

Some components in the REFPROPTM database, especially novel refrigerants, are not available in the CHEMCAD database. To use these fluids in CHEMCAD simulations, add them as user components.

  1. Select ADDK and ADDH in the CHEMCAD Thermodynamic Settings. CHEMCAD will then use REFPROPTM methods for vapor pressure and enthalpy calculations of the new component.
  2. In the CHEMCAD menu, navigate to Thermophysical -> Component Database -> Create New Component
  3. Locate the .FLD file of the component which you would like to add in the C:\Program Files (x86)\REFPROP\fluids folder of the REFPROPTM installation.
  4. In CHEMCAD, define the Component name to match the name of the related .FLD file. (e.g. Add R1233ZD.FLD in CHEMCAD as R1233ZD)
  5. Take the normal boiling point from the REFPROPTM fluid information screen (REFPROP menu: Substance -> Fluid Information)
  6. Use the default correlation Pseudocomponent to create the new component.
  7. After the creation of the new component, CHEMCAD shows the View/Edit Component Data dialog.
  8. Replace the values for critical properties in the Basic Data section with the data from REFPROPTM fluid information screen.
  9. For implementing the ideal gas heat capacity, create a Cp-T Diagram at P = 0 MPa in REFPROPTM. Use Edit -> Save Plot Data Points to generate a table.
  10. In CHEMCAD, navigate to Thermophysical -> Component Database -> Component Property Regression.
  11. Select your component and create a new regression for polynomial ideal gas heat capacity. Check that the same Engineering Units are selected in both tools.
  12. Copy-paste the table from REFPROPTM into CHEMCAD.

See Limitations for more details.


Examples for the REFPROPTM Flash Calculation

Example 1: Refrigeration Cycle

Use novel coolants for evaluation in refrigeration cycles. The simulation RP Example R1234 ze(E).cc7 shows a typical application of R1234 ze(E) for air conditioning. This case fixes the flowrate, the superheating of stream 4 and the pressures. Feel free to optimize this case for your application!

Download Refrigeration-Cycle.cc7

Example 2: Throttling of Methanol Vapor

Throttling commonly occurs in safety relief cases. Low temperature applications (e.g. Linde process) use throttling. Throttling is an effect of pressure drop in pipelines and valves. The simulation RP Example MeOH.cc7 shows how much a precise calculation of vapor enthalpies effects the Joule-Thomson coefficient and the temperature behind the throttle or relief valve. Compare these results with the results calculated with SRK or Latent Heat!

Download Throttling-of-MeOH.cc7

Examples for the REFPROPTM Property Calculation

Example 3: CO2 Pipeline

In the supercritical region the calculation of properties is difficult, as either DIPPR equations regressed to liquid properties must be extrapolated or Equations of State must be used. These methods are commonly not very accurate in estimating densities and viscosities. You may avoid these difficulties by using High Precision Equations of State. Therefore, reliable results can be obtained for the calculation of the pressure drop in a CO2 pipeline, operated in the supercritical region by using the REFPROPTM property calculation.

Download CO2-Pipeline.cc7

Example 4: Density of Water

The representation of liquid densities in a flowsheet simulator commonly is not very accurate. Equations of State often show a large deviation from measured data, as (most of them) do not have a parameter to fit real densities. Even the new VTPR equation fails for the calculation of the density of water at 1.013 bar and 4°C, although it has an adjustable volume parameter. Therefore, we recommend to use density functions from DIPPR. These are regressed to measured data in the subcritical region.

Table 1: Density of water at P = 1.013 bar and T = 4°C calculated with different models

Model SRK VTPR DIPPR REFPROPTM
Density 768 kg/m³ 1088 kg/m³ 1000 kg/m³ 1000 kg/m³

 

However, DIPPR considers only a temperature dependency and ignores the effect of pressure. And even though DIPPR uses up to seven parameters, it seems to be impossible to show the well-known density peak of water at 4°C AND to fit the density along the whole subcritical region with an acceptable accuracy. Using the REFPROPTM properties calculation package overcomes these problems:

Download Density-of-Water.cc7

Requirements for RefProp-Connector

Ref-Prop-Connector requires all the following steps:

  1. Install CHEMCAD 7.0.3 or above on your machine.
  2. Install REFPROPTM in the folder “C:\Program Files (x86)\REFPROP”. See the REFPROPTM website what licenses are available.
  3. Download and install our free CC-API Add-on manager.
  4. Purchase and install our “RefProp-Connector for CHEMCAD“.

Limitations of RefProp-Connector

  • REFPROPTM calculations are only available for streams with pure components.
  • In case of mixtures, the Soave-Redlich-Kwong (SRK) Equation of State for ADDK and ADDH, Mole% weighting for density mixing rule, and log average by mole fraction for viscosity mixing rule are the fallback methods.
  • Vapor densities calculation method is Soave-Redlich-Kwong (SRK) Equation of State.
  • Entropy calculation method is Soave-Redlich-Kwong (SRK) Equation of State. This affects isentropic unit operations like compressors, expanders and the isentropic flash mode. We recommend regressing the ideal gas heat capacities from REFPROPTM and running compressors and expanders in “Polytropic with ideal cp/cv” mode.
  • We recommend the usage of REFPROPTM property methods when REFPROPTM flash and equilibrium models are selected, since this leads to consistent results. However, it is possible to use e.g. the REFPROPTM liquid density calculation for the pressure drop in a PIPE unit operation while using NRTL, Latent Heat and DIPPR viscosity.
  • In the supercritical region (P > PC), CHEMCAD switches between a liquid density model (e.g. DIPPR) and a vapor density model (e.g. SRK) depending on a stream’s temperature. You can avoid potential problems in this region by using ADDK and ADDH when using REFPROP density calculation.

Changelog

Version 0.95: Published 31 August 2019

Version 1.0: Published 11 March 2020

New Features for RefProp-Connector

We are enhancing the functionality from time to time.

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RefProp-Connector FAQ

References

Lemmon, E.W., Bell, I.H., Huber, M.L., McLinden, M.O.  NIST Standard Reference Database 23:  Reference Fluid Thermodynamic and Transport Properties-REFPROP, Version 10.0, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, 2018.

Webinar

The recording of the webinar is available for all participants. Send an email to support@cc-api.com to get access!

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