Thermal Liquid Properties (TL)

Preset fluid properties for the simulation of a thermal liquid network

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  • Simscape / Fluids / Thermal Liquid / Utilities

Description

The Thermal Liquid Properties (TL) block applies to a thermal liquid network the properties of a fluid selected from a preset list. Preset fluids include pure water, aqueous mixtures—of saline, glycol and glycerol compounds, commonly used in heat transfer applications as coolants and antifreeze solutions—and fuels such as diesel and aviation-grade Jet A. Use this block as a simple alternative to the Thermal Liquid Settings (TL) block, to define a fluid without having to specify in detail all of its properties. Every thermal liquid network in a model must contain one instance of either of these blocks.

The preset fluid properties are defined in tabular form as functions of temperature and pressure. The table data is sourced from Coolprop—an open-source fluids database—or, in the case of seawater, from a computational model developed by (and proprietary to) MIT. The values of the properties are set during simulation by linear interpolation of the nearest tabulated breakpoints. The effect of concentration is factored into the property calculations for mixtures (with mass or volume fraction providing the necessary measure of concentration).

All the fluid properties commonly specified in the Thermal Liquid Settings (TL) block are defined in the block. These properties include density, the bulk modulus and thermal expansion coefficient, the specific internal energy and specific heat, as well as the kinematic viscosity and thermal conductivity. The properties are valid over a limited region of temperatures and pressures specific to the fluid selected and dependent, in the cases of mixtures, on the concentration specified. Simulation is allowed within this validity region only.

Data Visualization

A data visualization utility provides a means to graph the fluid properties defined in the block. Use it to examine the temperature and pressure dependencies of those properties or to ascertain the bounds of their validity regions (equal in the visualizations to the bounds of the plots). To open the visualization utility, right-click the block and from the context-sensitive menu select Fluids > Plot Fluid Properties. The plot updates automatically upon selection of a fluid property from the drop-down list. Use the Refresh button to regenerate the plot whenever the fluid selection or any of its required parameters are changed.

Visualization of density data for a 10% glycerol aqueous mixture

Validity Regions

The validity regions are defined in the block as matrices of zeros and ones. Each row corresponds to a tabulated temperature and each column to a tabulated pressure. A zero denotes an invalid breakpoint and a one a valid breakpoint. These validity matrices are internal to the block and cannot be modified; they can only be checked (using the data visualization utility of the block).

In most cases, the validity matrices are extracted directly from the tabulated data. Glycol and glycerol mixtures are a partial exception. Their pressure bounds are not available from the Coolprop data (where they are treated as incompressible fluids) and must therefore be obtained explicitly from block parameters. The figure shows an example of a validity region, that of pure water. Shaded squares are outside of the validity region.

Water

The properties of water are valid at temperatures above the triple-point value (273.160 K) up to the critical-point value (647.096 K). They are valid at pressures above the greater of the triple-point value (611.657 Pa) on one hand and the temperature-dependent saturation value on the other, up to the critical-point value (22,064,000 MPa). Pressures below the saturation point for a given temperature row are assigned a value of 0 in the validity matrix.

Seawater (MIT model)

The properties of seawater are valid at temperatures above 0°C up to 120°C (273.15 K to 393.15 K); they are valid at pressures above the saturation point up to a maximum value of 12 MPa. Pressures below the saturation point for a given temperature row (and at the specified concentration level) are assigned a value of 0 in the validity matrix. Mixture concentrations can range in value from 0 to 0.12 on a mass fraction basis.

Ethylene glycol and water mixture

The properties of an aqueous ethylene glycol mixture are valid over a temperature domain determined from the mixture concentration; they are valid at pressures within the minimum and maximum bounds specified in the block dialog box (extended horizontally to span the width of the temperature rows).

The lower temperature bound is always the lesser of the minimum temperature extracted from the Coolprop data and the freezing point of the mixture (the mixture must be in the liquid state). The upper temperature bound is always the maximum temperature extracted from the Coolprop data. Mixture concentrations can range in value from 0 to 0.6 if a mass-fraction basis is used, or from 0 to 1 if a volume fraction basis is used.

Propylene glycol and water mixture

The properties of an aqueous propylene glycol mixture are valid over the temperature and pressure ranges described for the case of Ethylene glycol and water mixture. Mixture concentrations can range in value from 0 to 0.6 if a mass-fraction basis is used, or from 0.1 to 0.6 if a volume fraction basis is used.

Glycerol and water mixture

The properties of an aqueous glycerol mixture are valid over the temperature and pressure ranges as described for the case of Ethylene glycol and water mixture. Mixture concentrations can range in value from 0 to 0.6 on a mass-fraction basis.

Diesel fuel

The properties of diesel fuel are valid at temperatures above -34.95°C up to 417.82°C (238.20 K to 690.97 K); they are valid at pressures above the saturation point up to a maximum value of 2.29 MPa. Pressures below the saturation point for a given temperature row are assigned a value of 0 in the validity matrix.

Aviation fuel Jet-A

The properties of Jet A fuel are valid at temperatures above -50.93°C up to 372.46°C (222.22 K to 645.61 K); they are valid at pressures above the saturation point up to a maximum value of 2.41 MPa. Pressures below the saturation point for a given temperature row are assigned a value of 0 in the validity matrix.

Density Calculations

The aqueous mixtures of glycol and glycerol compounds are treated in the Coolprop database as incompressible substances. Their bulk moduli are unavailable from the data and must instead be obtained from the block parameters (where they are specified as constants). The pressure dependencies of their thermal expansion coefficients are likewise missing and must therefore be calculated (using the bulk modulus provided). Let density be:

ρ(T,p)=dT(ρ(T,p)T)p+dp(dρ(T,p)dp)T,

where ρ is density, T is temperature, and p is pressure.

The solution has the form:

ρ(T,p)=ρ(T)exp(ppRβ),

where ß is the isothermal bulk modulus, and where the subscript R denotes a reference value, here the atmospheric pressure at which the bulk modulus is specified. The partial derivative of density with respect to temperature is:

(ρ(T,p)T)p=(ρ(T)T)Texp(ppRβ).

The thermal expansion coefficient is defined as:

α(T,p)=1ρ(T,p)(ρ(T,p)T)p,

Equivalently:

α(T,p)=1ρ(T,p)(ρ(T)T)Texp(ppRβ).

The block provides the thermal expansion coefficient in this form to the thermal liquid network of which it is a part.

Ports

Conserving

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Node identifying the thermal liquid network for which to define the necessary fluid properties. The fluid selected in this block applies to the entire network. No other Thermal Liquid Properties (TL) or Thermal Liquid Settings (TL) block may be connected to the same network.

Parameters

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Choice of preset fluid whose properties to use in the calculations of the connected thermal liquid network. The fluid properties are automatically set using an internal database derived from the Coolprop fluids library. The fluids provided include pure water, aqueous mixtures, and fuels.

Ratio of the mass of salt present in the saline mixture to the total mass of that mixture.

Dependencies

This parameter is active only when Seawater (MIT model) is selected as the working fluid.

Quantity in terms of which to specify the concentration of ethylene glycol in its aqueous mixture. This parameter is active only when either Ethylene glycol and water mixture or Propylene glycol and water mixture is selected as the working fluid.

Volume of ethylene glycol present in the aqueous mixture divided by the total volume of that mixture.

Dependencies

This parameter is active when Ethylene glycol and water mixture is selected as the working fluid and Volume fraction is selected as the concentration type.

Mass of ethylene glycol present in the aqueous mixture divided by the total mass of that mixture.

Dependencies

This parameter is active when Ethylene glycol and water mixture is selected as the working fluid and Mass fraction is selected as the concentration type.

Volume of propylene glycol present in the aqueous mixture divided by the total volume of that mixture.

Dependencies

This parameter is active when Propylene glycol and water mixture is selected as the working fluid and Volume fraction is selected as the concentration type.

Mass of propylene glycol present in the aqueous mixture divided by the total mass of that mixture.

Dependencies

This parameter is active when Propylene glycol and water mixture is selected as the working fluid and Mass fraction is selected as the concentration type.

Bulk modulus of the aqueous mixture at constant temperature. The bulk modulus measures the change in pressure required to produce a fractional change in fluid volume.

Dependencies

This parameter is active when either Ethylene glycol and water mixture, Propylene glycol and water mixture, or Glycerol and water mixture is selected as the working fluid.

Lower bound of the pressure range allowed in the thermal liquid network connected to this block.

Dependencies

This parameter is active when either Ethylene glycol and water mixture, Propylene glycol and water mixture, or Glycerol and water mixture is selected as the working fluid.

Upper bound of the pressure range allowed in the thermal liquid network connected to this block.

Dependencies

This parameter is active when either Ethylene glycol and water mixture, Propylene glycol and water mixture, or Glycerol and water mixture is selected as the working fluid.

Absolute pressure of the external environment in which the thermal liquid network is assumed to run. The default value is the standard atmospheric pressure measured at sea level on Earth.

References

[1] Massachusetts Institute of Technology (MIT), Thermophysical properties of seawater database. http://web.mit.edu/seawater.

[2] K.G. Nayar, M.H. Sharqawy, L.D. Banchik, J.H. Lienhard V, Thermophysical properties of seawater: A review and new correlations that include pressure dependence, Desalination, Vol. 390, pp. 1-24, 2016.

[3] M.H. Sharqawy, J.H. Lienhard V, S.M. Zubair, Thermophysical properties of seawater: A review of existing correlations and data, Desalination and Water Treatment, Vol. 16, pp. 354-380.

[4] I.H. Bell, J. Wronski, S. Quoilin, V. Lemort, Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp, Industrial & Engineering Chemistry Research, Vol. 53 (6), pp. 2498–2508, 2014.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Introduced in R2018a