Contents - Index


Brines

 

Brines are also called secondary refrigerants.  These fluids are mixtures of water and another substance that results in a reduction of the freezing point of the fluid.  The property functions applicable to brines and the units of the value that the function returns are:

 

Cp [kJ/kg-K] or [Btu/lbm-R]

Conductivity [W/m-K] or [Btu/hr-ft-R]

Density [kg/m^3] or [lbm/ft^3]

Enthalpy  [kJ/kg] or [Btu/lbm]

FreezingPt [C], [K], [F], or [R]

IntEnergy [kJ/kg] or [Btu/lbm]

MolarMass_soln [kg/kmol or Btu/lbmol]

Prandtl [-]

SpecHeat [kJ/kg-K] or [Btu/lbm-R]   (same as Cp}

Viscosity [Pa-s] or [lbm/ft-hr]

Volume [m^3/kg] or [ft^3/lbm]

Pressure [Pa], [kPa], [bar], [MPa], [psia], or [atm], depending on EES setting for pressure

 

The first parameter for all of these property functions must be the name of the mixture provided as a string constant or string variable.  (Quotes around the string constant are not required.)  The fluid mixture names for which data are provided are:

 

Name Complete Name Temp. Range Conc. Range

CACL2 Calcium Chloride-Water -40C - 40C 0 to 30%

EA Ethyl Alcohol-Water -45C - 40C 0 to 60%  

EG Ethylene Glycol-Water -51C - 125C 0 to 60%

GLYC Glycerol-Water -40C - 40C 0 to 60%

K2CO3 Potassium Carbonate-Water -40C - 40C 0 to 40%  

KAC Potassium Acetate-Water -33.5C - 40C 0 to 45%

KFO Potassium Formate-Water -33.5C - 40C 0 to 48%

LICL Lithium Chloride-Water -75C - 40C 0 to 24%

MA Methyl Alcohol-Water -73C - 40C 0 to 60%

MGCL2 Magnesium Chloride-Water -33.5C - 40C 0 to 30%

NACL Sodium Chloride-Water -33.5C - 40C 0 to 23%

NH3W Ammonia-water -40C - 30C 0 to 30%

PG Propylene Glycol-Water -50C - 135C 0 to 60%

 

The next one, two or three parameters are the temperature,  mass concentration, expressed as a percentage, and the pressure.  Concentration (in % on a mass basis) is required for all of the property functions.  The FreezingPt and MolarMass_soln functions require no other parameters.   The temperature must be supplied for all functions other than FreezingPt and MolarMass_Soln in the units specified in the Unit System dialogThe pressure is required only for the Enthalpy function.  It is ignored with a warning message if it is provided for any of the other property functions.  These parameters can be provided in any order. 

 

If EES is configured in molar units, then the specific properties of a brine solution will be returned on a molar basis.  However, the concentration must always be supplied in % on a mass basis. 

 

Example:

$UnitSystem SI C kPa kJ

rho=density(EG,T=25 [C],C=20 [%])

{Solution: rho=1022 [kg/m^3]}

 

Note that the FreezingPt function requires only one parameter in addition to the fluid name, e.g.,

$UnitSystem SI C kPa kJ

FP=freezingPt(EG,C=20 [%])

{Solution:  FP=-7.949 [C]}

 

However, the FreezingPt function will accept T as an input and ignore the value.

 

Note that the Enthalpy function requires inputs of temperature, composition and pressure.

$UnitSystem SI C kPa kJ

h=enthalpy(EG,T=25 [C], C=20[%], P=200 [kPa])

{Solution: h=73.56 [kJ/kg]}

 

 

Most of the correlations used in EES for brine properties were obtained from Properties of Secondary Working Fluids for Indirect Systems, IIF/IIR, Melinder, 2010, http://www.iifiir.org/en/details.php?id=1177

 

Vapor pressure data are from the following sources.

1.  Conde, M., 2009, Aqueous Solutions of Lithium and Calcium Chlorides: - Property formulations for use in Air Conditioning Equipment Design, http://www.mrc-eng.com/Downloads/Aqueous%20LiCl&CaCl2%20Solution%20Props.pdf   (for LiCl and CaCl2)

2.  Patil, K.R., Tripathi, A.D., Pathak, G., and Katti, S.S., "Thermodynamic Properties of Aqueous Electrolyte Solutions.  2. Vapr pressure of Aqueous Solutions of NaBr, NaI, KCl, KBr, KI, RbCl, CsCl, CsBr, CsI, MgCl2, CaCl2, BaBr2, CaI2, SrCl2, SrBr2, SrI2, BaCl2, and BaBr2", J. Chem. Eng. Data, (1991), 36, 225-230 (lfor MgCl2)

3. Soujanya, J, Satyavathi, B., and  Prasad, T.E. Vittal, "Experimental (vapour + liquid) equilibrium data of (methanol + water), (water + glycerol) and (methanol + glycerol) systems at atmospheric and sub-atmospheric pressures", J. Chem. Thermodynamics, 42 (2010) 621-624 {for methanol and water and glycerol and water}

4. Fujuta, T. and Kikuchi, S, "Vapor pressure of Aqueous Solutions of Ethylene Glycol", Trans. of the Japan Society of Refrigerating and Air Conditioning Engineers, (2011), Vol 6, pp. 183-186 (for ethylene glycol and water}

5.  Verlinde, J.R., Verbeeck, R.M.H., and Thun, H.P., "Density and Vapour Pressure of the Propylene Glycol-water system from 15C to 15C", Bull. SOC. Chim. Belg. vol. 84/11. 11/1975 {for PG}

6.  Springer International Publishing AG 2017 235  T. Elmer, A Novel SOFC Tri-generation System for Building Applications, Springer Theses, DOI 10.1007/978-3-319-46966-9 {for KFO}

7.  Chou, J.C., Thermodynamic Properties of Aqueous Sodium Chloride SOlutions from 32 F to 350 F, PhD thesis, Oklahoma State University, July 1968  {for NACL}

 

 

The enthalpy change of mixing for calcium chloride solutions is from M. Conde Engeering, 2009, "Aqueous Solutins fo Lithium and Calcium Chlorides: Property Formulations for use in Air Conditioning Equipment Design", http://www.mrc-eng.com/Downloads/Aqueous%20LiCl&CaCl2%20Solution%20Props.pdf

 

Specific internal energy and specific enthalpy are available for some brines for which enthalpy of mixing information data were available.  In this case, the specific internal energy is referenced to 0 for pure water at 0C.  The specific internal energy at a specified temperature and concentration is found by adding the enthalpy of mixing at 0C (and low pressure) at the specified concentration to the integral of the specific heat capacity with temperature.  Specific enthalpy is determined as the sum of the specific internal energy and the product of pressure and specific volume, in consistent units.

 

A plot of brine properties versus temperature at specified concentrations can be automatically generated with the Property Plot command.

 

Note:  Brine properties in older versions of EES were provided with the BrineProp2 external procedure.  The brine property data in EES is based on newer correlations than used in BrineProp2.  However, BrineProp2 is provided with EES for backward compatibility.