Solutions
Solutions in EES refer to a binary mixtures consisting of a solid or liquid (the solute) that are dissolved in water (the solvent). Solutions are often used as a secondary refrigerants (sometimes referred to as brines) since the addition of a substance to water can result in a reduction of the freezing point. The property functions applicable to solutions and the units of the result 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]
NormalBoilingPt [C], [K], [F], [R]
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
Saturation% [%]
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 -40 C - 40 C 0 to 30%
EA Ethyl Alcohol-Water -45 C - 40 C 0 to 60%
EG Ethylene Glycol-Water -51 C - 125 C 0 to 60%
GLYC Glycerol-Water -40 C - 40 C 0 to 60%
K2CO3 Potassium Carbonate-Water -40 C - 40 C 0 to 40%
KAC Potassium Acetate-Water -33.5 C - 40 C 0 to 45%
KFO Potassium Formate-Water -33.5 C - 40 C 0 to 48%
KOH Potassium Hydroxide 0 C - 200 C 0 to 50%
LICL Lithium Chloride-Water -75 C - 40 C 0 to 24%
MA Methyl Alcohol-Water -73 C - 40 C 0 to 60%
MGCL2 Magnesium Chloride-Water -33.5 C - 40 C 0 to 30%
NACL Sodium Chloride-Water -33.5 C - 40 C 0 to 25%
NaOH Sodium Hydroxide 0 C - 200 C 0 to 50%
NH3W Ammonia-water -40 C - 30 C 0 to 30%
PG Propylene Glycol-Water -50 C - 135 C 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 except for the Saturation% function which return the concentration at saturation and requires only the temperature. The FreezingPt, NormalBoilingPt and MolarMass_soln functions require no other parameters. The temperature must be supplied for all other functions in the units specified in the Unit System dialog. The 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 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]}
"!Note that the Saturation% function requires only one parameter,i.e., temperature, in addition to the fluid name, e.g.,"
$UnitSystem SI C
SatC=saturation%(NaCl,T=0 [C])
{Solution: SatC=26.28 [C]}
Most of the correlations used in EES for solution properties (excepting KOH and NaOH) were obtained from: Properties of Secondary Working Fluids for Indirect Systems, IIF/IIR, Melinder, 2010
Data for KOH and NaOH are from:
1. Damien Le Bideau et al., Review of necessary thermophysical properties and their sensivities with temperature and electrolyte mass fractions for alkaline water electrolysis multiphysics modelling
Internaltional Journal of Hydrogen Energy 44 (2019 ) 4553-4579
2. Sergii Bespalko, Experimental Study of the Thermal Effect of the Dissolution Reaction for Some Alkalis and Salts with Natural Mixing and Forced Stirring
E3S Web of Conferences 118, 01026 (2019) https://doi.org/10.1051/e3sconf/201911801026
3. J. BALEJ, Water Vapour Partial Pressures And Water Activities In Potassium And Sodium Hydroxide Solutions Over Wide Concentration and Temperature Ranges
Int. J. Hydrogen Energy, Vol. 10., No. 4, pp. 233-243, 198gen Energy, Vol. 10, No. 4, pp. 233-243, 1985.nt. J. Hydrogen Energy, Vol. 10, No. 4, pp. 233-243, 1985.es IN
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 (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 15 C to 15 C", 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}
Saturation% data are from the following sources.
1. https://en.wikipedia.org/wiki/Solubility_table
2. https://www.proquest.com/docview/302415843?pq-origsite=gscholar&fromopenview=true.
The enthalpy change of mixing for calcium chloride solutions is from M. Conde Engeering, 2009, "Aqueous Solutions for Lithium and Calcium Chlorides: Property Formulations for use in Air Conditioning Equipment Design".
Specific internal energy and specific enthalpy are available for some solutions for which enthalpy of mixing information data were available. In this case, the specific internal energy is referenced to 0 for pure water at 0 C. The specific internal energy at a specified temperature and concentration is found by adding the enthalpy of mixing at 0 C (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 solution properties versus temperature at specified concentrations can be automatically generated with the Property Plot command.