npss refprop thermodynamic property package user...

Numerical Propulsion System Simulation Consortium

NPSS™ REFPROP Thermodynamic Property

Package User Guide

Software Release: NPSSTM_2.4.1 Doc. #: NPSSTM–Thermo

Doc Revision: 1 Revision Date: June 21, 2012

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Doc. #: NPSSTM Thermo Guide

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Table of Contents PREFACE ..................................................................................................................... 2

1 REFPROP ............................................................................................................. 3

1.1 CREATING A REFPROPFLOWSTATION ......................................................................... 4

1.2 FLUID COMPOSITION ................................................................................................ 4

1.3 FLOWSTATION THERMODYNAMIC PROPERTIES ............................................................. 10

1.4 FLOWSTATION STATIC PROPERTIES ............................................................................ 13

1.5 FLOWSTATION ADD AND COPY FUNCTIONS .................................................................. 15

List of Tables Table 1-1: REFPROPFlowStation Defaults and Assumptions ................................................ 4

Table 1-2: List of REFPROPFlowStation Supported Parameters ...................................... 18

Table 1-3: List of REFPROPFlowStation Switches .................................................................. 22

Table 1-4: List of REFPROPFlowStation Functions ................................................................ 22


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Preface This document is a user guide for the thermal dynamic property packages and is intended to be used in

conjunction with the NPSS User Guide Reference Sheets.

Calculations involving fluid properties require a thermodynamics package that models the fluid. NPSS

offers the user the ability to choose the thermodynamics package to be used.

NOTE: The REFPROPFlowStation is currently only supported for the Windows system.


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1 REFPROP REFPROP is an acronym for REFerence fluid PROPerties, and it is a commercially available software

package developed by the National Institute of Standards and Technology (NIST). The REFPROP software

comes with a graphical user interface as well as a "refprop.dll" file that may be utilized to interface with

other languages and applications such as FORTRAN, C++, and Excel. REFPROP also comes with files that

contain fluid property information for several pure fluids (".fld" extension, in the "fluids" directory),

pseudo-pure fluids (".ppf" extension, in the "fluids" directory), and predefined mixtures (".mix" extension,

in the "mixtures" directory). The REFPROP software and related files DO NOT COME WITH NPSS; the

user must contact NIST to purchase his/her own copy of REFPROP in order for the NPSS

REFPROPFlowStation to work.

The NPSS REFPROPFlowStation is an interface to REFPROP in the form of an NPSS FlowStation, which

means that it has similar look, feel, and functionality of other NPSS FlowStations (such as allFuel, Janaf,

etc.). In order for the REFPROPFlowStation to work the user must own a copy of REFPROP and place the

"reprop.dll" file, "mixtures" directory, and "fluids" in the desired model's local directory. Once that is done,

the user may proceed to create an NPSS model and set the thermodynamic property package to REFPROP,

create FlowStations and Elements as desired, set the fluid composition as desired, and run the model. The

REFPROPFlowStation will look for the "refprop.dll" and fluid file directories in the model's local

directory. Figure 1 depicts an example of placing the "reprop.dll" file and "fluids" and "mixtures"

directories in the local model directory.

Figure 1. Example of placing "refprop.dll" and "fluids"

and "mixtures" directories in local directory

REFPROP, and therefore the REFPROPFlowStation, runs fast if the composition is set to a pure fluid or a

pseudo-pure fluid. However, execution speed slows when composition comprises multiple fluids, whether

set via a predefined mixture file (".mix" extension) or defined manually via the FlowStation comp attribute.

The speed impact is especially evident when static properties are calculated because multiple internal calls

to REFPROP are required.

The REFPROPFlowStation was developed and tested using REFPROP version 8.0 (NIST Standard

Referenc Database 23). It has not been tested using any other versions of REFPROP and is not guaranteed

to work with any other versions. While the REFPROPFlowStation has been designed to report errors

generated by the REFPROP code, it is always a good idea to test fluids out using the REFPROP graphical

interface, especially when defining new mixtures.

The REFPROPFlowStation will only work on the Windows operating system.

Some defaults and assumptions have been built into the REFPROPFlowStation, as shown in Table 1-1.

Some of these values can be changed and some cannot.


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Table 1-1: REFPROPFlowStation Defaults and Assumptions

Item Description Default Changeable? Fluid model The model used for

fluid equation of

state thermodynamic

and transport

properties

NBS – use NIST

recommendation

for specified

fluid/mixture

No

Mixture

coefficient

file name

File that contains

binary mixing

coefficients

hmx.bnc No, the file name is

fixed as "hmx.bnc", but

the contents of the file

can be changed.

REFPROP dll

and fluid

file

locations

The location of the

"refprop.dll" file,

"fluids" directory,

and "mixtures"

directory

Model's local

directory

No

Reference

State Method

The method used to set

the fluid's reference

state temperature,

pressure, enthalpy,

and entropy.

OTH – other,

user specified

for real fluid

No, the reference state

method is always set to

OTH. However, the user

may change the reference

state using the

FlowStation function

"setRefState"

Tref Reference state

temperature

518.69 R Yes, using the


"setRefState"

Pref Reference state

pressure

14.696 R Yes, using the


"setRefState"

hRef Reference state

enthalpy

0.0 Btu/lbm Yes, using the


"setRefState"

sRef Reference state

entropy

0.0 Btu/lbm*R Yes, using the


"setRefState"

1.1 Creating a REFPROPFlowStation

The thermo package must be set before any FlowStation objects can be created. If the thermo package is

already set to “REFPROP” then it does not need to be set again before creating a REFPROP FlowStation.

The setThermoPackage function is used to set the thermo package. The "refprop.dll" file and "fluids" and

"mixtures" directories must exist in the model's local directory.

// Specify REFPROP thermo package

setThermoPackage("REFPROP");

After the thermo package is set FlowStations can be created as usual.

// Create FlowStation(s)

FlowStation FS;

FlowStation FS2;

1.2 Fluid Composition

The REFPROP software package comes with three different file types that define fluid properties: pure

fluid files have a ".fld" extension, predefined mixture files have a ".mix" extension, and pseudo-pure fluid


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files have a ".ppf" extension. A single ".fld" file is used to set the composition to a pure fluid, a single

".ppf" file is used to set the composition to a pseudo-pure fluid, and a single ".mix" file is used to set the

composition to a predefined mixture. Multiple ".fld" files may be used to define a mixture, but ".ppf" and

".mix" files cannot be used in conjunction with each other or other ".fld" files.

If the composition is to be set to a mixture of fluids, then the FlowStation's comp variable should contain

"mass" or "mole" at the end of the string. If mass or mole is not specified, then the fractions entered in

the comp string will be treated on a mole basis.

Setting the Composition

Once a REFPROPFlowStation has been created its composition is set using the comp string variable. The

formal syntax for setting comp using pure fluid files uses the following comma-delimited format: fluid file

fluid's mass or mole fraction, then repeat for the next fluid if the composition is a mixture of other pure

fluid files. The final value of comp is "mole" or "mass" preceded by a comma, as shown below:

FlowStation.comp = "fluid1.fld, frac1, fluid2.fld, frac2, mass or mole"

Pure Fluids

Composition may be set to a pure fluid as follows:

// Set FS composition to pure water

FS.comp = "water.fld, 1.0, mole";

Because the example above has a composition of a single pure fluid (water), specifying a mole or mass

fraction is not necessary. In fact, if it is not set to 1.0 the FlowStation will throw a warning message.

Therefore, a FlowStation's composition may be set to a pure fluid without specifying the mole or mass

fraction.

// Set FS composition to pure water (fraction not specified)

FS.comp = "water.fld"; // 1.0 fraction implied, mole/mass not applicable

Moreover, pure fluids do not require the ".fld" file extension to be specified, so the previous example may

be written as follows:

// Set FS composition to pure water (no mole fraction

FS.comp = "water"; // .fld assumed, 1.0 fraction implied

Mixtures of Pure Fluids

Mixture composition may be set on a mass basis using ".fld" files as follows. Note that the last constituent

is followed by a comma and the word "mass".

// Set composition to 24% oxygen, 76% nitrogen on a mass basis

FS.comp = "oxygen.fld, 0.24, nitrogen.fld, 0.76, mass";

Mixture composition may be set on a mole basis using ".fld" files as follows. Note that the last constituent

is followed by a comma and the word "mole".

// Set composition to 22% oxygen, 78% nitrogen on a mole basis

FS.comp = "oxygen.fld, 0.22, nitrogen.fld, 0.78, mole";

Because fluid files do not require the ".fld" extension to be specified, the previous example can be written

as follows:


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// Set composition to 22% oxygen, 78% nitrogen on a mole basis

FS.comp = "oxygen, 0.22, nitrogen, 0.78, mole"; // .fld files assumed

Predefined Mixtures

The REFPROP "mixtures" directory contains several predefined fluid mixture files (".mix" extension) that

essentially list the fluid files and mole fractions that comprise a mixture. Figure 2 shows the mixture file

"R401A.mix," which happens to comprise three pure fluids: R22, R152, and R124. In this example file, the

pertinent information read in by the REFPROPFlowStation is on lines 3 through 9. Line 3 is the number of

components (in this example, three), lines 4 through 6 lists the fluid files ("R22.fld", "R152A.fld", and

"R124.fld"), and lines 7 through 9 list the respective fluid mole fractions. Lines 1 and 2 contain information

used by the REFPROP software graphical interface but not by REFPROPFlowStation. However, the

REFPROPFlowStation still requires that the mixture file format is consistent, with the number of

components specified on line 3, followed by the fluid files and mole fractions.

Figure 2. Example predefined mixture file "R401A.mix"

for Refrigerant R401A

You may create your own predefined mixture file for use in the REFPROPFlowStation using the same

format as shown in Fig. 2. The fluid fractions MUST BE SPECIFED ON A MOLE BASIS. For example, a

predefine mixture file for 22% oxygen and 78% nitrogen (mole basis) would be written as shown in Fig. 3.

Line 1 contains the mixture name (not used by REFPROPFlowStation), line 2 contains mixture molecular

weight and critical point (not used by REFPROPFlowStation, so all are set to 0.0), line 3 denotes the

number of components (two), lines 4 and 5 list the fluid files, and lines 6 and 7 list the respective fluid mole

fractions. Save the new file in the "mixtures" directory and give it a ".mix" extension.

Figure 3. Example custom predefined mixture file for 22% oxygen,

78% nitrogen on a mole fraction basis

To set the FlowStation's composition using a mixture file, simply set comp equal to the name of the mixture

file. Note that constituent fractions listed in the mixture file MUST BE IN MOLE FRACTIONS.

// Set composition using predefined mixture file

FS.comp = "air.mix";


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Notice in the example above that FS.comp did not require a mole fraction to be entered because the

mixture mole fractions are already defined in the "air.mix" file. In fact, any mole fraction specified in comp

would have been ignored.

Composition may only be set using one mixture file. If multiple mixture files are specified the first will be

used, the other(s) will be ignored, and the FlowStation will throw a warning. For example, the code below

will result in "R401A.mix" being used to defined the fluid mixture and will ignore the "R401B.mix" file

and two mole fractions specified. The following example should be avoided:

// Try setting composition using two predefined mixture file

// !!!! Second file and two mole fractions will be ignored !!!!

FS.comp = "R401A.mix, 0.5, R401B.mix, 0.5, mole"; // will throw warning

Predefined mixture files may not be used in conjunction with ".fld" or ".ppf" files. Doing so will result in a

FlowStation error. The following example is not allowed:

// Try setting comp using a predefined mixture file and pure fluid file

FS.comp = "air.mix, 0.5, nitrogen.fld, 0.5, mole"; // NOT ALLOWED !!!

Pseudo-pure Fluids

The REFPROP "fluids" directory also contains files that define a handful of pseudo-pure fluids (".ppf"

extension) such as AIR, R404, R407C, R410A, and R507A. Even though these fluids are technically

mixtures of other pure fluids, the ".ppf" files contain all the information necessary for REFPROP to treat

these fluids as if they were pure fluids, which means the computation time is much faster than mixtures

defined using a collection of fluid files (".fld") or predefined mixture file (".mix"). However, pseudo-pure

fluid files and compositions cannot be changed or mixed with any other fluid files. FlowStation

composition may be set using a pseudo-pure fluid file as follows:

// Set composition using pseudo-pure fluid file

FS.comp = "air.ppf";

Notice in the example above that a mole fraction is not specified because a mole fraction of 1.0 is implied.

In fact, any mole or mass fraction specified in comp would have been ignored.

Composition may only be set using one pseudo-pure fluid file. If multiple pseudo-pure fluid files are

specified the first will be used, the other(s) will be ignored, and the FlowStation will throw a warning. For

example, the code below will result in "R404A.ppf" being used to define the fluid mixture and will ignore

the "R407C.mix" file and two mole fractions specified. This is should be avoided:

// Try setting composition using two predefined mixture file

// !!!! Second file and two mole fractions will be ignored !!!!

FS.comp = "R404A.ppf, 0.5, R407C.ppf, 0.5, mole"; // will throw warning

Pseudo-pure fluid files may not be used in conjunction with ".fld" or ".mix" files. Doing so will result in a

FlowStation error.

// Try setting comp using a predefined mixture file and pure fluid file

// !!!! THIS IS NOT ALLOWED !!!!

FS.comp = "air.ppf, 0.5, nitrogen.fld, 0.5"; // will throw an error

Each FlowStation is a separate object and nothing is shared between REFPROPFlowStations, therefore,

each FlowStation can have its own composition. Below is an example of setting three different

FlowStations (FS1, FS2, and FS3) to three different compositions.


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// Set FS1 composition to pure water

FS1.comp = "water"; // assumes .fld file

// Set FS2 composition to pseudo-pure fluid R410A

FS2.comp = "R410A.ppf";

// Set FS3 composition to mixture of oxygen and nitrogen, mole basis

FS3.comp = "oxygen, 0.22, nitrogen, 0.78, mole"; // assumes .fld files

Retrieving the Composition

Once composition is set the FlowStation can be queried for the composition, constituent fluid names, fluid

file names, molecular weight, and mole and mass fraction. A complete list of FlowStation attributes is

presented in Table 1-2.

The following example sets the composition to 22% oxygen and 78% nitrogen on a mole basis and queries

the FlowStation for various composition-related attributes. Note that if comp is asked for, the returned

string will contain the fluid file names (converted to all capital letters) and the constituent fractions will be

on a mass or mole basis as indicated by "MASS" or "MOLE" at the end of the string. The fraction basis

will reflect the basis that was used to originally set comp. // Set FS composition to mixture of oxygen and nitrogen

FS.comp = "oxygen, 0.22, nitrogen, 0.78, mole"; // assumes .fld files

// Print composition string

cout << "comp = " << FS.comp << endl;

Returns the following string. Note that the end of the string indicates that composition was set using mole

fractions.

comp = "OXYGEN.FLD, 0.22, NITROGEN.FLD, 0.78, MOLE"

Ask for list of mixture constituents, compFluids:

// Print composition constituents

cout << "compFluids = " << FS.compFluids << endl;

Returns the following string array. Note that fluid names have been converted to upper case for

consistency.

compFluids = {"OXYGEN", "NITROGEN"}

Ask for mixture mass and mole fractions: compMassFrac and compMoleFrac. Note that the fractions are

in the same order is the same as the compFluids string array.

// Print composition mass fractions and mole fractions

cout << "mass fractions = " << FS.compMassFrac << endl;

cout << "mole fractions = " << FS.compMoleFrac << endl;

Returns the real arrays:

mass fractions = { 0.243672, 0.756328, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0, 0 }

mole fractions = { 0.22, 0.78, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0 }

If composition is set using a predefined mixture file and then the value of comp is asked for, comp will

return the mixture's ".fld" fluid file names and not the ".mix" file name.


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// Set composition using predefined mixture file

FS.comp = "air.mix";

Now ask for the value of comp:

// Print composition string (will return mole fractions)

cout << "comp = " << FS.comp << endl;

Returns the comp string in mole fractions:

comp = "NITROGEN.FLD, 0.781200, ARGON.FLD, 0.009200,

OXYGEN.FLD, 0.209600, MOLE"

Setting Composition in a Model

Many models will utilize a FlowStart element to initiate the fluid flow. The following example shows

how to instantiate FlowStart, Duct, and FlowEnd elements, link them together, and set fluid composition

in the FlowStart element's Fl_O fluid output port. Note that composition will get passed from element to

element via the fluid port linkages.

// Instantiate a FlowStart element named FsWater

Element FlowStart FsWater {

// Set temperature, pressure, and flow rate

Tt = 520;

Pt = 14.7;

W = 5.;

// Set fluid composition at the fluid output port

Fl_O.comp = "water"; // pure water

}

// Instantiate a Duct element named D010

Element Duct D010;

// Instantiate a FlowEnd element named FeWater

Element FlowEnd FeWater;

// Link the elements together

linkPorts("FsWater.Fl_O", "D010.Fl_I", "F010");

linkPorts("D010.Fl_O", "FeWater.Fl_I", "F020");

// Run the model

run();

// Print composition at F010 and F020

cout << "F010.comp = " << F010.comp << endl;

cout << "F020.comp = " << F020.comp << endl;

The example model above will run and print the results shown below. Notice that station F010 and F020

compositions are the same because composition was passed from the FlowStart, to the Duct, to the

FlowEnd.

F010.comp = "WATER.FLD, 1.0, MOLE"

F020.comp = "WATER.FLD, 1.0, MOLE"


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1.3 FlowStation Thermodynamic Properties

After a REFPROPFlowStation has been declared and its composition has been defined, the thermodynamic

state may be set using one of the following functions. Table 1-4 lists all of the supported

REFPROPFlowStation functions:

- setTotalTP(Tt, Pt) – set total conditions using total temperature and total pressure

- setTotal_hP(ht, Pt) – set total conditions using total enthalpy and total pressure

- setTotalSP(s, Pt) – set total conditions using entropy and total pressure

- setTotal_hS(ht, s) – set total conditions using total enthalpy and entropy

- setTotal_xP(xt, Pt) – set total conditions using total two-phase quality (mass basis) and total

pressure

- setTotal_xT(xt, Tt) – set total conditions using total two-phase quality (mass basis) and total

temperature

- setTotalTsPsMN(Ts, Ps, MN) – set total and static conditions using static temperature, static

pressure, and Mach number

- setTotalTsPsV(Ts, Ps, V) – set total and static conditions using static temperature, static

pressure, and velocity

- setTotal_hsPsV(hs, Ps, V) – set total and static conditions using static enthalpy, static


The following example sets the thermo package to REFPROP, creates a FlowStation, sets the composition

to pure nitrogen, and sets the total conditions using temperature and pressure:



// Create FlowStation

FlowStation FS;

// Set FS composition to pure nitrogen

FS.comp = "nitrogen";

// Set total condition using temperature and pressure

FS.setTotalTP(600, 20); // 600 R, 20 psia

After the total condition has been set the FlowStation can be queried for other total properties such as

enthalpy, density, entropy, etc. Table 1-2 lists all of the REFPROPFlowStation attributes.

// Print FlowStation enthalpy, density, and entropy

cout << "ht = " << FS.ht << " " << FS.ht.units << endl;

cout << "rhot = " << FS.rhot << " " << FS.rhot.units << endl;

cout << "s = " << FS.s << " " << FS.s.units << endl;

Returns the values:

ht = 20.2174 Btu/lbm

rhot = 0.0870072 lbm/ft3

s = 0.0143515 Btu/(lbm*R)

The values for enthalpy and entropy in the example above reflect a default reference state of 518.67 R,

14.696 psia, 0.0 Btu/lbm, and 0.0 Btu/lbm*R. Reference state can be change via the setRefState

function. However, caution should be used when changing the reference state because two FlowStations

cannot be added (via the add function) unless both FlowStations have the same reference temperature,

pressure, and enthalpy. Reference state can be changed as follows:


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// Change reference temperature, pressure, enthalpy and entropy

FS.setRefState(500, 100, 20, 5); // 500 R, 100 psia,

// 20 Btu/lbm, 5 Btu/lbm*R

REFPROPFlowStation has the ability to handle fluids that are superheated, supercritical, subcooled,

saturated liquid, saturated vapor, and two-phase liquid-vapor. The setTotalTP function cannot be used to

set the state to two-phase, but the setTotal_hP, setTotalSP, setTotal_hS, setTotal_xP, and

setTotal_xT can be used to set the state to two-phase. For example, the setTotal_xT function uses

total quality (mass basis) and pressure to set the state as follows:

// Create FlowStation

FlowStation FS2;

// Set composition to pure water

FS2.comp = "water";

// Set state to 90% quality (mass basis) at 118 psia

FS2.setTotal_xP(0.90, 118);

Ask for some fluid properties (state is currently two-phase liquid-vapor):

cout << "xt = " << FS.xt << endl;

cout << "Pt = " << FS.Pt << endl;

cout << "Tt = " << FS.Tt << endl;

cout << "ht = " << FS.ht << endl;

cout << "rhot = " << FS.rhot << endl;

cout << "PtSat = " << FS.PtSat << endl; // saturation pressure at Tt

cout << "TtSat = " << FS.TtSat << endl; // saturation temp at Pt

cout << "hSatL_Pt = " << FS.hSatL_Pt << endl; // sat liq. enthalpy at Pt

cout << "hSatV_Pt = " << FS.hSatV_Pt << endl; // sat vapor enthalpy at Pt

Returns the values:

xt = 0.9

Tt = 799.66

Pt = 118

rhot = 0.293106

ht = 1076.13

PtSat = 118

TtSat = 799.66

hSatL_Pt = 284.304

hSatV_Pt = 1164.11

Figure 4 is a plot of water at 90% quality and 118 psia on a temperature-enthalpy diagram. The diagram

shows that TtSat is approximately 800 R, which agrees with the value for TtSat printed in the example

above. The plotted points for ht, hSatL_Pt, and hSatV_Pt also agree with the results of the example

above.


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0

200

400

600

800

1000

1200

1400

1600

-200 0 200 400 600 800 1000 1200 1400 1600

Tem

per

atu

re, R

Enthalpy, Btu/lbm

Liquid Two-phase Vapor

Supercritical

90% quality, 118 psia

Sat. Liq. enthalpy(hSatL_Pt)

Sat. Vap. enthalpy(hSatV_Pt)

Critical Point

Figure 4. Water T-h diagram with state at 90% quality and 118 psia

Note that values returned for Cp, Cv, gamma, Vsound, mu, and k are not valid for two-phase fluid. Cp, Cv,

gamma, and Vsound will typically return negative values. For example:

cout << "Cpt = " << FS.Cpt << endl;

cout << "Cvt = " << FS.Cvt << endl;

cout << "gamt = " << FS.gamt << endl;

cout << "Vsoundt = " << FS.Vsoundt << endl;

Will return:

Cpt = -132667 (not valid)

Cvt = -132667 (not valid)

gamt = -132667 (not valid)

Vsoundt = -3.28081e+007 (not valid)

The example above used quality to set the fluid's total state. The input quality for setTotal_xP and

setTotal_xT must be 0 < x < 1.0, inclusive. If the two-phase state was set using a function such as

setTotal_hP, the output value for quality may take on a value below 0.0 or above 1.0 to indicate that the

fluid is a subcooled liquid (negative value), superheated vapor (positive value), or supercritical fluid (998

or 999), but the value for quality in these regions is otherwise meaningless.

Some models might require the solver to drive a particular cycle state point to saturated liquid or saturated

vapor condition. For example, to target a saturated vapor condition a solver dependent could be employed

to drive fluid quality equal to 1.0 (xt = 1.0) or drive enthalpy equal to saturated vapor enthalpy (ht =

hSatV_Pt). Similarly, to target a saturated liquid condition a solver dependent could be employed to drive

enthalpy equal to saturated liquid enthalpy (ht = hSatL_Pt). However, caution should be used when

driving quality to 0.0 (xt = 0.0) for two reasons: 1) targeting a value of 0.0 requires an additional solver

dependent attribute to be set, namely eq_Ref, and 2) the solver may converge on a quality just below 0.0

due to the solver tolerance but produce results far from the true saturated liquid point, because small

changes in quality for subcooled liquids (negative value) can result in large changes in fluid properties.

Another important item to keep in mind when using the solver and two-phase fluids is that for a given

pressure, temperature is constant under the vapor dome (Tt = TtSat) because phase change is an

isothermal process (this is why setTotalTP cannot be used to set a two-phase state). Therefore, if the

solver is trying to drive a particular cycle state point equal a temperature close to TtSat, the solver could


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throw an error if during the convergence process the fluid becomes two-phase. The error would likely

report that Tt is not affected by any solver independents.

1.4 FlowStation Static Properties

Once the flow rate and total conditions have been set, the static condition can be calculated by setting any

one of the following: area (A), static enthalpy (hs), static pressure (Ps), static temperature (Ts), or Mach

number (MN) , Velocity (V). Note that Mach number cannot be used to set the static condition for a two-

phase fluid because speed of sound is not valid in the two-phase region.

The following example sets the composition to pure hydrogen, sets flow rate, sets the total condition using

the setTotalTP function (liquid phase in this example), and then sets the static condition using velocity.

// Create FlowStation named FS

FlowStation FS;

// Set composition to pure hydrogen

FS.comp = "hydrogen";

// Set flow rate

FS.W = 20; // lbm/sec

// Set state to 30 R, 14.7 psia (subcooled liquid)

FS.setTotalTP(30, 14.7);

// Set velocity. This will set the flow static conditions.

FS.V = 10; // ft/sec

// Print some FlowStation properties to the command window

cout << "Pt = " << FS.Pt << " , Ps = " << FS.Ps << endl;

cout << "Tt = " << FS.Tt << " , Ts = " << FS.Ts << endl;

cout << "rhot = " << FS.rhot << " , rhos = " << FS.rhos << endl;

cout << "ht = " << FS.ht << " , hs = " << FS.hs << endl;


cout << "W = " << FS.W << endl;

cout << "V = " << FS.V << endl;

cout << "MN = " << FS.MN << endl;

cout << "A = " << FS.A << endl;

Returns the values:

Pt = 14.7 , Ps = 14.6497

Tt = 30 , Ts = 29.9998

rhot = 4.66543 , rhos = 4.66542

ht = -1644.05 , hs = -1644.05

xt = -5.61595e-006

W = 20

V = 10

MN = 0.00251132

A = 61.7308

The following example sets the composition to pure water, sets flow rate, sets the total condition using the

setTotalTP function (superheated vapor phase in this example), and then sets the static condition using

Mach number.

// Create FlowStation named FS

FlowStation FS;

// Set composition to pure water


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FS.comp = "water";

// Set flow rate

FS.W = 5; // lbm/sec

// Set total condition to 1000 R, 50 psia (superheated vapor)

FS.setTotalTP(1000, 50);

// Set Mach number. This will set the flow static condition.

FS.MN = 0.8;







cout << "W = " << FS.W << endl;

cout << "V = " << FS.V << endl;


cout << "A = " << FS.A << endl;

Returns the values:

Pt = 50 , Ps = 33.5596

Tt = 1000 , Ts = 910.996

rhot = 0.084735 , rhos = 0.0624117

ht = 1277.48 , hs = 1235.87

xt = 26.6127

W = 5

V = 1443.39

MN = 0.8

A = 7.9925

FlowStations support design and off-design mode, which is set via the switchDes option variable. During

design mode (default), the static parameter set (Ps, Ts, hs, V, MN, or A) will be honored even if the total

condition changes. However, once the FlowStation is switched to off-design mode, area (A) becomes the

static parameter that will be adhered to unless one of the other static parameters is explicitly set during off-

design mode, in which case area will be recalculated. The area used during off-design is the last known

value for area.

The following example is a continuation of the previous static condition example above, which used

superheated water as the fluid. Recall that Mach number was the input static parameter, which resulted in

an area of 7.9925 in2 for the given flow rate of 5 lbm/sec and total condition of 1000 R, 50 psia. The

FlowStation will now be set to off-design mode, and the total condition and flow rate will be manually

changed.

// Switch the FlowStation to OFFDESIGN

FS.switchDes = "OFFDESIGN"; // locks in area value

// Change total conditoin to 800 R, 40 psia (superheated vapor)

FS.setTotalTP(800, 40);

// Change flow rate

FS.W = 2; // lbm/sec, new flow rate






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cout << "W = " << FS.W << endl;

cout << "V = " << FS.V << endl;


cout << "A = " << FS.A << endl;

Returns the values:

Pt = 40 , Ps = 38.2788

Tt = 800 , Ts = 791.717

rhot = 0.0855616 , rhos = 0.0827382

ht = 1180.88 , hs = 1177.09

xt = 3.10802

W = 2

V = 435.515

MN = 0.259802

A = 7.9925

Notice in the results above that the total and static conditions have changed, as have velocity and Mach

number. However, area remains the same as the previous (design) point because the FlowStation is now in

off-design mode.

1.5 FlowStation add and copy Functions

Table 1-4 lists all of the supported REFPROPFlowStation functions. A few functions that allow

FlowStations to transfer information from one station to another are copyFlow, copyFlowStatic, and

add. One requirement for all of these functions is that both FlowStations involved must of the same type,

in this case REFPROPFlowStation. Therefore, you cannot perform and add or copy between a

REFPROPFlowstation and a GasTblFlowStation.

The copyFlow function accepts one string argument that specifies the FlowStation from which to copy.

The parameters that get copied are composition, total condition, flow rate, and reference state. If the

primary FlowStation already has composition, flow rate, etc. set, copyFlow will overwrite those values.

The following example shows how to use the copyFlow function to copy attributes from FS1 to FS2.



// Create two FlowStations

FlowStation FS1;

FlowStation FS2;

// Set FS1 composition to 24% oxygen, 76% nitrogen on a mass basis

FS1.comp = "oxygen.fld, 0.24, nitrogen.fld, 0.76, mass";

// Set FS2 composition to pure water

FS2.comp = "water";

// Set FS1 state to 700 R and 20 psia

FS1.setTotalTP(700, 20);

// Copy the attributes from FS1 to FS2

FS2.copyFlow("FS1");


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In the example above, FS2.comp was originally set to "water" and total condition was not set. After the

call to copyFlow, FS2 composition is no longer "water"; it is now "oxygen.fld, 0.24,

nitrogen.fld, 0.76, mass". The total condition is now 700 R and 20 psia.

The copyFlowStatic function copies everything that copyFlow does and additionally copies the static

condition. The example below is a continuation of the example above.

// Set FS1 static pressure

FS1.Ps = 18; // psia

// Copy the total AND static conditions from FS1 to FS2

FS2.copyFlowStation("FS1");

The add function may be used to add one flow to another, conserving energy and mass but not momentum.

The resulting pressure is the same as the primary FlowStation's total pressure. Three requirements for the

add function to work are that both FlowStations must be of the same type (REFPROPFlowStation), both

must have the same reference state (Tref, Pref, and hRef), and must both have their composition defined

using pure fluid files (".fld"), which may have originally been set using predefined mixture files (".mix").

FlowStations can be also be added if both compositions were set using the same pseudo-pure fluid file

(".ppf"). For example, both have a composition of "air.ppf".

The following example adds a secondary flow with a composition of oxygen and argon at 600 R and 14

psia to a primary flow with a composition of nitrogen and oxygen.

// Set FS1 composition, total condition, and flow rate

FS1.comp = "nitrogen.fld, 0.8,oxygen.fld, 0.2, mass";

FS1.setTotalTP(600, 14); // T=600(R), P=14(psia)

FS1.W = 1.0; // lbm/sec


FS2.comp = "oxygen.fld, 0.95, argon.fld, 0.05, mass";

FS2.setTotalTP(700,20); // T=700(R), P=20(psia)

FS2.W = 0.5;

// Print some FS1 and FS2 properties before performing the add

cout<< endl <<"---- FS1 props (before add) -------" << endl<< endl;

cout<<"FS1.Tt = "<<FS1.Tt<<endl;

cout<<"FS1.Pt = "<<FS1.Pt<<endl;

cout<<"FS1.ht = "<<FS1.ht<<endl;

cout<<"FS1.W = "<<FS1.W<<endl;

cout<<"FS1.MW = "<<FS1.MW<<endl;

cout << "comp = " << FS1.comp << endl;

cout << "compMassFrac = " << FS1.compMassFrac << endl;

cout << "compMoleFrac = " << FS1.compMoleFrac << endl;

cout<< endl <<"---- FS2 props -------" << endl<< endl;









// ============= Add FS2 to FS1 =============


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FS1.add("FS2");

// Print some FS1 properties after the add

cout<< endl <<"---- FS1 props (after add) -------" << endl<< endl;









Returns the results:

---- FS1 props (before add) -------

FS1.Tt = 600

FS1.Pt = 14

FS1.ht = 19.7826

FS1.W = 1

FS1.MW = 28.7291

comp = NITROGEN.FLD, 0.800000, OXYGEN.FLD, 0.200000, MASS

compMassFrac = { 0.8, 0.2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0 }

compMoleFrac = { 0.820436, 0.179564, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0 }

---- FS2 props -------

FS2.Tt = 700

FS2.Pt = 20

FS2.ht = 39.2835

FS2.W = 0.5

FS2.MW = 32.3204

comp = OXYGEN.FLD, 0.950000, ARGON.FLD, 0.050000, MASS

compMassFrac = { 0.95, 0.05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0 }

compMoleFrac = { 0.959547, 0.0404531, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0 }

---- FS1 props (after add) -------

FS1.Tt = 630.904

FS1.Pt = 14

FS1.ht = 26.2829

FS1.W = 1.5

FS1.MW = 29.8341

comp = NITROGEN.FLD, 0.533333, OXYGEN.FLD, 0.450000, ARGON.FLD,

0.016667, MASS

compMassFrac = { 0.533333, 0.45, 0.0166667, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0, 0 }

compMoleFrac = { 0.567995, 0.419558, 0.0124471, 0, 0, 0, 0, 0, 0, 0, 0,

0, 0, 0, 0, 0, 0, 0, 0, 0 }

Notice in the results above that the primary FlowStation (FS1) flow rate is increased (1.0 + 0.5 = 1.5

lbm/sec), the enthalpy and temperature increased, nitrogen mass (and mole) fraction decreased, oxygen

mass (and mole) fraction increased, and argon has been added as a constituent. Properties for the secondary

FlowStation (FS2) were not printed because FS2 was not affected by the add function.


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The example below shows how the add function can be used with two FlowStations that have the same

pseudo-pure fluid composition.


FS1.comp = "air.ppf";


FS1.W = 1.0;


FS2.comp = "air.ppf";


FS2.W = 0.5;

// Add FS2 to FS1

FS1.add("FS2"); // both fluids have air.ppf composition

Table 1-2: List of REFPROPFlowStation Supported Parameters

Name Units I/O Description A in2 I/O Physical cross sectional area. Can be

used to set static conditions.

Cps Btu/(lbm*R) O Constant pressure specific heat, based on

static conditions. Not valid for two-

phase fluid.

Cpt Btu/(lbm*R) O Constant pressure specific heat, based on

total conditions. Not valid for two-phase

fluid.

Cvs Btu/(lbm*R) O Constant volume specific heat, based on

static conditions. Not valid for two-

phase fluid.

Cvt Btu/(lbm*R) O Constant volume specific heat, based on

total conditions. Not valid for two-phase

fluid.

comp I/O String variable that sets and returns the

composition fluids and mass or mole

fractions, as indicated by "MASS" or

"MOLE" at the end of the string.

compFluids O String array of the constituent fluids

compFileNames O String array of the fluid property files.

Order is the same as compFluids string

array.

compMassFrac O Real array of composition mass fractions.


array.

compMoleFrac O Real array of composition mole fractions.


array.

description I FlowStation description

gams O Specific heat ratio (Cv/Cp) based on

static conditions

gamt O Specific heat ratio (Cv/Cp) based on

total conditions

hs Btu/lbm I/O Enthalpy based on static conditions. Can

be used to set static conditions.

ht Btu/lbm O Enthalpy based on total conditions

hCrit Btu/lbm O enthalpy at the critical point

hRef Btu/lbm O Reference state enthalpy. Default is 0.0

Btu/lbm. Can be changed using the flow


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station setRefState function.

hSatV_Ps Btu/lbm O Saturated vapor enthalpy at current

static pressure. Applies to single and

two-phase fluids.

hSatV_Pt Btu/lbm O Saturated vapor enthalpy at current total

pressure. Applies to single and two-phase

fluids.

hSatL_Ps Btu/lbm O Saturated liquid enthalpy at current


two-phase fluids.

hSatL_Pt Btu/lbm O Saturated liquid enthalpy at current

total pressure. Applies to single and

two-phase fluids.

hSatV_Ts Btu/lbm O Saturated vapor enthalpy at current

static temperature. Applies to single and

two-phase fluids.

hSatV_Tt Btu/lbm O Saturated vapor enthalpy at current total

temperature. Applies to single and two-

phase fluids.

hSatL_Ts Btu/lbm O Saturated liquid enthalpy at current


two-phase fluids.

hSatL_Tt Btu/lbm O Saturated liquid enthalpy at current

total temperature. Applies to single and

two-phase fluids.

iDescription I

ks Btu/(sec*ft*R) Thermal conductivity based on static

conditions. Not valid for two-phase

fluid.

kt Btu/(sec*ft*R) Thermal conductivity based on total


fluid.

MN I/O Mach number. Can be used to set static

conditions for single-phase fluid.

MNdes I Design Mach number. Can be used to set

static conditions for single-phase fluid.

mus lbm/(ft*sec) O Viscosity based on static conditions. Not

valid for two-phase fluid.

mut lbm/(ft*sec) O Viscosity based on total conditions. Not

valid for two-phase fluid.

MW O Molecular weight

PminLimit_EOS psia O Pressure min limit for the equation of

state calculations

PmaxLimit_EOS psia O Pressure max limit for the equation of

state calculations

PminLimit_k psia O Pressure min limit for thermal

conductivity calculation

PmaxLimit_k psia O Pressure max limit for thermal


PminLimit_mu psia O Pressure min limit for viscosity

calculation

PmaxLimit_mu psia O Pressure max limit for viscosity

calculation

Prs O Prandtl number based on static


fluid.

Prt O Prandtl number based on total conditions.

Not valid for two-phase fluid.

Ps psia I/O Static pressure. Can be used to set

static conditions.

Pt psia O Total (stagnation) pressure


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Pcrit psia O Pressure at the critical point

Pref psia O Reference state pressure. Default is

14.696 psia. Can be changed using the

flow station setRefState function.

PsMelt psia O Melting pressure for the current static

temperature

PtMelt psia O Melting pressure for the current total

temperature

PsSat psia O Saturation pressure for the current

static temperature

PtSat psia O Saturation pressure for the current total

temperature

rhos lbm/ft3 O Density based on static conditions

rhot lbm/ft3 O Density based on total conditions

rhoCrit lbm/ft3 O Density at the critical point

rhoSatV_Ps lbm/ft3 O Saturated vapor density at current static

pressure

rhoSatV_Pt lbm/ft3 O Saturated vapor density at current total

pressure

rhoSatL_Ps lbm/ft3 O Saturated liquid density at current

static pressure.

rhoSatL_Pt lbm/ft3 O Saturated liquid density at current total

pressure

rhoSatV_Ts lbm/ft3 O Saturated vapor density at current static

temperature

rhoSatV_Tt lbm/ft3 O Saturated vapor density at current total

temperature

rhoSatL_Ts lbm/ft3 O Saturated liquid density at current

static temperature

rhoSatL_Tt lbm/ft3 O Saturated liquid density at current total

temperature

Rs Btu/(lbm*R) O Gas constant based on static conditions

Rt Btu/(lbm*R) O Gas constant based on total conditions

s Btu/(lbm*R) O Entropy

sRef Btu/(lbm*R) O Reference state entropy. Default is 0.0

Btu/(lbm*R). Can be changed using the

flow station setRefState function.

sSatV_Ps Btu/lbm O Saturated vapor entropy at current static


fluids.

sSatV_Pt Btu/lbm O Saturated vapor enthalpy at current total


fluids.

sSatL_Ps Btu/lbm O Saturated liquid enthalpy at current


two-phase fluids.

sSatL_Pt Btu/lbm O Saturated liquid enthalpy at current

total pressure. Applies to single and

two-phase fluids.

sSatV_Ts Btu/lbm O Saturated vapor enthalpy at current


two-phase fluids.

sSatV_Tt Btu/lbm O Saturated vapor enthalpy at current total

temperature. Applies to single and two-

phase fluids.

sSatL_Ts Btu/lbm O Saturated liquid enthalpy at current


two-phase fluids.

sSatL_Tt Btu/lbm O Saturated liquid enthalpy at current

total temperature. Applies to single and

two-phase fluids.


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TminLimit_EOS R O Temperature min limit for the equation of

state calculations

TmaxLimit_EOS R O Temperature max limit for the equation of

state calculations

TminLimit_k R O Temperature min limit for thermal


TmaxLimit_k R O Temperature max limit for thermal


TminLimit_mu R O Temperature min limit for viscosity

calculation

TmaxLimit_mu R O Temperature max limit for viscosity

calculation

Ts R I/O Static temperature. Can be used to set

static conditions.

Tt R O Total (stagnation) temperature

Tcrit R O Temperature at the critical point

Tref R O Reference state temperature. Default is

518.67 R. Can be changed using the flow

station setRefState function.

TsMelt R O Melting temperature for the current

static pressure

TtMelt R O Melting temperature for the current total

pressure

TsSat R O Saturation temperature for the current

static pressure

TtSat R O Saturation temperature for the current

total pressure

us Btu/lbm O Internal energy based on static

conditions

ut Btu/lbm O Internal energy based on total conditions

V ft/sec I/O Flow velocity. Can be used to set static

conditions.

Vsounds ft/sec O Speed of sound based on static


fluid.

Vsoundt ft/sec O Speed of sound based on total conditions.

Not valid for two-phase fluid.

W lbm/sec I Total weight flow

Wc lbm/sec O Corrected weight flow.

W*sqrt(theta)/delta

Wp lbm/sec O Referred weight flow. W*sqrt(T)/P

xs lbm/lbm O Two-phase quality based on static

conditions, mass basis (lbm vapor / lbm

total).

x = 0 indicates saturated liquid,

x = 1 indicates saturated vapor,

0 < x < 1 indicates two-phase fluid,

x < 0 indicates subcooled (compressed)

liquid,

x > 1 indicates superheated vapor,

x = 998 indicates superheated vapor, but

quality not defined (Ts > Tcrit),

x = 999 indicates supercritical state

(Ps > Pcrit and Ts > Tcrit)

xt lbm/lbm O Two-phase quality based on total

conditions, mass basis (lbm vapor / lbm

total).

x = 0 indicates saturated liquid,

x = 1 indicates saturated vapor,


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0 < x < 1 indicates two-phase fluid

x < 0 indicates subcooled (compressed)

liquid,

x > 1 indicates superheated vapor,

x = 998 indicates superheated vapor, but

quality not defined (Tt > Tcrit),

x = 999 indicates supercritical state

(Pt > Pcrit and Tt > Tcrit)

xsMole mole/mole O Same as xs except on a mole basis (moles

vapor / moles total)

xtMole mole/mole O Same as xt except on a mole basis (moles

vapor / moles total)

Table 1-3: List of REFPROPFlowStation Switches

Name Description Default Allowed

Values superOrSub Determines if static

conditions are for subsonic

or supersonic solution

SUBSONIC SUBSONIC,

SUPERSONIC

switchDes Determines if the

FlowStation is in design or

off-design mode

DESIGN DESIGN,

OFFDESIGN

Table 1-4: List of REFPROPFlowStation Functions

Name Return

Type

Arguments Description

add void stationName Add in a secondary flow station of the

same type. Conserve mass and energy but

not momentum. Pressure remains the same

as the primary flow station. Flow

composition is updated (comp,

compFluids, compFileNames, compMassFrac,

compMoleFrac). FlowStation reference

states (Tref, Pref, and hRef) must be

the same.

copyFlow void stationName Copy primary attributes (composition,

weight flow, total condition, and

reference state) from another station in

the same object scope to this one

copyFlowRemote void stationName Copy primary attributes (composition,

weight flow, total condition, and

reference state) from another station

anywhere in the model to this one

copyFlowStatic void stationName Copy primary and static attributes

(composition, weight flow, total and

static conditions, and reference state)

from another station in the same object

scope to this one

getStationType string Returns FlowStation type

("REFPROPFlowStation")

setRefState void Tref, Pref,

hRef, sRef

Sets the fluid's reference state

temperature, pressure, enthalpy, and

entropy (Tref, Pref, hRef, sRef).

Default reference state is 518.67 R,

14.696 psia, 0.0 Btu/lbm, 0.0 Btu/lbm*R.

Use with caution because the "add"


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function requires that the two fluids

being added have the same reference

state.

setTotalTP void Tt, Pt Sets fluid total conditions based on

total temperature and total pressure

setTotal_hP void ht, Pt Sets fluid total conditions based on

total enthalpy and total pressure

setTotal_hS void ht, s Sets fluid total conditions based on

total enthalpy and entropy

setTotalSP void s, Pt Sets fluid total conditions based on

entropy and total pressure

setTotalTsPsMN void Ts, Ps, MN Sets fluid total and static conditions

based on static temperature, static

pressure, and Mach number

setTotal_hsPsV void hs, Ps, V Sets fluid total and static conditions

based on static enthalpy, static


setTotalTsPsV void Ts, Ps, V Sets fluid total and static conditions

based on static temperature, static


setTotal_xT void xt, Tt Sets fluid total conditions based on

total condition two-phase quality (mass

basis) and total temperature

setTotal_xP void xt, Pt Sets fluid total conditions based on

total condition two-phase quality (mass

basis) and total pressure

NPSSTM Software © Copyright 2003. The U.S. Government, as Represented by the Administrator of the National

Aeronautics and Space Administration (NASA);

NPSSTM Software © Copyright 2008, 2009, 2010. The Ohio Aerospace Institute, on behalf of the NPSSTM

Consortium. All rights reserved. Includes content licensed from the U.S. Government, National Aeronautics and

Space Administration under United States Copyright Registration Numbers V3503D364 and V3482D344.

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