packagePropyleneGlycolWater
Extends from Modelica.Media.Interfaces.PartialSimpleMedium.
Information
This medium package models propylene glycol - water mixtures.
The mass density, specific heat capacity, thermal conductivity and viscosity are assumed constant and evaluated at a set temperature and mass fraction of propylene glycol within the mixture. The dependence of the four properties are shown on the figure below.
The accuracy of the thermophysical properties is dependent on the temperature variations encountered during simulations. The figure below shows the relative error of the the four properties over a 10 °C range around the temperature used to evaluate the constant properties. The maximum errors are 0.8 % for mass density, 1.5 % for specific heat capacity, 3.2 % for thermal conductivity and 250 % for dynamic viscosity.
The figure below shows the relative error of the the four properties over a 20 °C range around the temperature used to evaluate the constant proepties. The maximum errors are 1.6 % for mass density, 3.0 % for specific heat capacity, 6.2 % for thermal conductivity and 950 % for dynamic viscosity.
The enthalpy is computed using the convention that h=0 if T=0 °C.
Limitations
Density, specific heat capacity, thermal conductivity and viscosity are constant. The propylene glycol/water mixture is modeled as an incompressible liquid. There are no phase changes. The medium is limited to temperatures below 100 °C and mass fractions below 0.60. As is the case for BuildingSystems.Media.Water, this medium package should not be used if the simulation relies on the dynamic viscosity.
Typical use and important parameters
The temperature and mass fraction must be specified for the evaluation of the constant thermophysical properties. A typical use of the package is (e.g. for a temperature of 20 °C and a mass fraction of 0.40):
Medium = BuildingSystems.Media.Antifreeze.PropyleneGlycolWater(property_T=293.15, X_a=0.40)
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Temperature | property_T | Temperature for evaluation of constant fluid properties | |
| Modelica.Units.SI.MassFraction | X_a | Mass fraction of propylene glycol in water |
Contents
| Name | Description |
|---|---|
| BaseProperties | Base properties |
| density_TX_aprotected | Evaluate density of antifreeze-water mixture |
| dynamicViscosity_TX_aprotected | Evaluate dynamic viscosity of antifreeze-water mixture |
| fusionTemperature_TX_aprotected | Evaluate temperature of fusion of antifreeze-water mixture |
| polynomialPropertyprotected | Evaluates thermophysical property from 2-variable polynomial |
| specificHeatCapacityCp_TX_aprotected | Evaluate specific heat capacity of antifreeze-water mixture |
| thermalConductivity_TX_aprotected | Evaluate thermal conductivity of antifreeze-water mixture |
Revisions
-
October 26, 2018, by Filip Jorissen and Michael Wetter:
Now printing different messages if temperature or mass fraction is above or below its limit, and adding instance name as JModelica does not print the full instance name in the assertion. This is for #1045. -
March 16, 2018, by Massimo Cimmino:
First implementation.