THERMOPTIM® software

Overall presentation What's new The interactive charts THERMOPTIM® software

Principles of model building List of available pure substances Distribution addresses A new educational philosophy

Overall presentation

The THERMOPTIM series is a set of software tools dedicated to the learning and better understanding of applied thermodynamics. It is comprised of:

• initiation modules in the form of Java applets
• easy to use interactive charts: ideal gases, vapors, mixtures of an ideal gas and of water vapor (psychrometrics)
• a modeling environment including four closely interconnected working environments : a diagram editor (graphical modeler), a simulator, the interactive charts, and an optimization tool

Whereas the analysis of energy technologies and thermodynamics are generally considered as difficult fields, it is possible to greatly simplify matters by separating the overall system description, which is generally vrather simple, from the study of the various components considered one by one.

The overall description is very useful at the qualitative level: it is visual and allows one to understand the role of each component in the whole system. On the instructional level, it is of basic importance to understand the design principles of these technologies. Once the overall structure of an engine or a refrigeration device is well understood, it is much easier to study its components one by one because one knows how each is included in the system and what its function is.

If one has access to an appropriate graphical environment such as that which is provided in THERMOPTIM, the internal structure of any system can be very easily described. The qualitative or diagrammatic representation which is obtained is full of engineering information that can subsequently be quantified it by setting the numerical thermodynamic parameters of the various components.

Thanks to this novel approach separating qualitative and quantitative aspects, THERMOPTIM's users are allowed to easily calculate even complex thermodynamic systems without writing an equation or programming a single line of code.THERMOPTIM is applied thermodynamics software whose objective is to allow one to easily calculate complex thermodynamic cycles without making very simplistic hypotheses or without being involved in tedious calculations. Initially it has been developed to help solve problems encountered in teaching applied thermodynamics. Its present functionalities make it possible to use it for also solving much more complicated problems such as industrial schematic design (for instance it has been used for the system integration of advanced electricity generation production plants involving several hundreds of components).

What's new

Since April 1998, when Thermoptim was first distributed, the main improvements that have been made have focussed first on vapor modeling. New equations have been used in order to achieve significant accuracy gains in the vapor zone for pressures close to or greater than the critical pressure.

Initially developed under 4th Dimension ® (ACI SA), THERMOPTIM has now been translated (1999) into Java ®.
The automatic recalculation engine of this version allows one to easily perform sensitivity analyses on complex systems: THERMOPTIM is indeed able, when the user modifies one of the various component parameters or state variables, to automatically derive which elements have to be recalculated and in which order the recalculation should be done. This powerful function allows one to optimize systems much more easily than before.

A graphical interface was developed in 2000. This diagram editor, which allows one to qualitatively describe the systems under investigation includes a palette comprised of any Thermoptim's components; these can be displayed (process-points, heat exchanges, compressors, expansion devices, combustion chambers, throttling expansion valves, mixers, dividers, separators) on a working panel in which these components are located and connected by links. This graphical environment provides a user-friendliness of great interest for viewing large projects and controlling internal linkages. Furthermore, it allows for simpler data entry when creating a new project.

The interactive charts

The interactive charts have been developed with a view to replace classical paper thermodynamic charts. Indeed, whatever care is taken by editors in the choice of color sets for distinguishing the various curves shown on the classical charts, it is always difficult to read them, and interpolation may lead to significant errors. New THERMOPTIM charts allow one, by a simple mouse click, to display all relevant thermodynamic properties of the fluid, thus providing better accuracy. Their main asset is to be very easy to use: the thermodynamic properties are immediately displayed on the screen, a user-friendly point editor allows the user to refine his/her cycle analysis and to export the values in spreadsheets or text editors.

As of this release, the following charts are available:

- vapor charts, which cover, either in temperature/entropy (T,s) or in enthalpy/pressure (h,p) coordinates, the liquid, liquid-vapor equilibrium and vapor zones, for seventeen pure substances, including steam.

- ideal gas temperature/entropy (T,s) charts in which one can modify the gas composition.

- psychrometric charts in which one can modify either the pressure or the dry gas composition (for air as well as pure or compound gases, such as combustion flue gases).

The THERMOPTIM software package

THERMOPTIM provides a modeling environment comprised of closely interconnected simulation functions as well as an optimization method allowing one to easily vary the whole set of characteristics of the system under investigation.

Since energy conversion technologies can be represented as an assembly of interconnected components, their system analysis can be based on a combination of a system design for the studied project, which allows one to bring to the fore its main functional elements and their interconnections, and a steady-state thermodynamic modeling of its various elements. To make these calculations one needs:

• each functional element represented by an appropriate Thermoptim basic type (substance, point, process, node, heat exchanger) which has its own characteristics and coupling variables

• the whole system model assembled from these types using an interactive interface

• the system simulation of the whole made possible thanks to an automatic recalculation engine which exploits the system properties that were implicitly described when the system was initially modeled (in the Java version).

THERMOPTIM has been developed to help solve some difficulties related to the learning and better understanding of applied thermodynamics. Its objectives are the following:

• motivate beginners by avoiding initial calculation difficulties while enabling them to study examples complex enough to represent real world cases

• facilitate the understanding of the software thanks to a powerful user interface and the inclusion of a large number of features

• provide advanced users with a powerful calculation environment allowing them to improve their productivity

Applied thermodynamics is indeed a relatively complex science, the physical laws being very nonlinear. Thermodynamic fluids are either ideal gases or vapors. The first are relatively easy to model as compared to the second because they are governed by much more complex equations.

These fluids undergo various transformations, themselves also nonlinear, from the simplest like compressions or expansions, to more complex ones leading to composition changes, such as combustion or moist gas condensations.

Main functions of the software

THERMOPTIM allows one to calculate the complete state of different fluids (temperature, pressure, mass volume, enthalpy, internal energy, entropy, exergy and quality), for ideal gases and condensable vapors. These fluids can undergo various transformations or processes:

• compression and expansion, in open or closed systems. These can be adiabatic or polytropic, and are characterized by their isentropic or polytropic efficiency.

• combustion, also in a closed or open system, at set pressure, volume or temperature. Fuel can be introduced into the combustion chamber separately from the oxidizer, or premixed. The dissociation of the carbon dioxide can be taken into account.

• heat exchanges with other fluids: the software is able to calculate the UA product or the overall heat transfer coefficient across the surface of a heat exchanger for the following configurations: counter flow, parallel flow, cross flow or (p-n) type. Once a heat exchanger is designed, its off design operation can also be determined.

• throttling

Fluid networks are represented by nodes (mixers, dividers and separators), which conserve enthalpy and mass flow-rate. The other elements (compressors, turbines, combustion chambers, heat exchangers) can be easily connected into these networks.

Fluid mixtures can be made. These are considered to be ideal gases. Specifically, THERMOPTIM allows one to process water vapor / gas mixtures and provides six types of processes to study them (heating, cooling, humidification, supply conditions, desiccation).

The software possesses a database of thermophysical properties of substances most commonly used in applied thermodynamics.

Thermoptim demonstration version

The Thermoptim demonstration version is distributed as a freeware. It has the following restrictions:

• restricted number of substances,

• number of points and processes limited to 10,

• all data saving functions are disabled, but it is possible however to read any already composed Thermoptim project (whatever its size),

• chart intercativity is suppressed, but the charts can still be used to plot cycles designed in the simulator

Principles of model building

Building the model of a thermodynamic system with Thermoptim is a very simple two step process:

• one starts by qualitatively describing the system graphically representing it as a set of components (more generally functionalities) connected together by links corresponding to fluid conduits and heat exchangers.
• then one subsequently quantifies the model obtained by setting values of the parameters of the various basic types involved.

The diagram editor enables the user to undertake a qualitative design: at this stage the user enters a minimal amount of information requested to logically define the project (implicitly the types of the components selected on the palette, and explicitely their names, the outlet points and substances associated, as well as the flow rate involved). Subsequently, when a user connects these components together, key information is automatically transferred (for instance the inlet point of a component is set equal to the outlet point of the upstream component to which it is connected).

Once this phase is completed, it is possible to transfer the components to the simulator in order to instantiate the necessary primitive types, along with a default setting of their thermodynamic parameters. The model can then be quantified in detail with each simulator element being displayed easily by double-clicking either on the component in the diagram editor, or in a table within the main project frame.

Advantages and limits of THERMOPTIM

As compared to other existing software in this field, THERMOPTIM presents the following advantages and limits:

• it provides a consistent modeling environment combining the inputs of systemic and analytical approaches. With a relatively small initial time investment, necessary to understand the underlying logic of the tool, itself rather natural and intuitive, it allows one to adopt readily a rigorous analysis method leading to significant productivity gains. The models developed can easily be documented, saved and modified.

• its basic component set enables one to easily model a large variety of different thermodynamic systems, from simple cycles to complex utilities. Very rapidly, the modeler is able to easily represent an energy technology in a way which is at the same time close to reality and calculable by the software.

• the description of the problem is made by using natural engineering concepts, the primitive types having a clear physical feel. The modeler can therefore concentrate on the physical analysis of the system because the mathematical and numerical translation of the model is created automatically by the software.

• the modeler does not write a single line of code, nor does he solve any equation, Thermoptim takes care of the coding of the project described. The user thus gets realistic results without any programming errors. If he or she wants to make calculations which are not included in the software, this is possible by using the output files provided, with a spreadsheet for example.

• as fluid properties are automatically calculated, the modeler can get very accurate results without being hindered by calculation difficulties nor by making unrealistic assumptions.

• thanks to its recalculation engine, the user can automatically simulate complex processes and cycles.

The two main limits of THERMOPTIM are the following:

• generally in the current version, pressures and flow rates are not automatically calculated by the software: the modeler has to set them in each of the primitive types used. by the software: the modeler has to set them in each of the primitive types used.

• the modeling is for steady state conditions. To make more detailed studies, in particular in transient conditions, it is necessary to use specialized tools.

List of available pure substances

Vapors

Water*, Ammonia*, Nitrogen, Butane*, Ethane, Carbon dioxide, Helium, Methane*, Propane*, R11* (trichlorofluoromethane CCl3F), R12* (dichlorodifluoromethane CCl2F2), R123 (2,2-dichloro-1,1,1-trifluoroethane CHCl2-CF3), R13* (chlorotrifluoromethane CClF3), R134a* (1,1,1,2-tetrafluoroethane C2H2F4), R141b (1,1-dichloro-1-fluoroethane CH3Cl2-CF), R22* (chlorodifluoromethane CHClF2), R245fa (1,1,1,3,3-pentafluoropropane C3H3F5)

Ideal gases

Ar*, CO*, CO2*, H2*, H2O*, H2S*, He*, N2*, O2*, SO2*, SO3*, CH4* (methane), C2H6* (ethane), C3H8* (propane), C4H10* (n-butane), C5H12 (pentane), C6H14 (hexane), C7H16 (heptane), C8H18 (octane)

Note : the substances with an * are available in the demonstration version, the others not.

Distribution addresses

The professional distribution of the THERMOPTIM series is made by:

interactive charts and Java version (CSTB)

• interactive charts on CD-ROM (Techniques de l'Ingénieur)

• interactive charts and Java version via Internet (PSCICO Inc)

A new educational philosophy

Instructors know that teaching thermodynamics can be significantly improved by the use of Educational Software Tools. Applied thermodynamics is indeed a relatively complex science, as the physical laws are nonlinear and the thermodynamic properties of the fluids are difficult to model, in particular for vapors.

Students are often faced from the beginning with complex calculation problems which may discourage them because the final goal of these efforts is not clear at the start of the course. For want of adequate tools, teachers are often led, in order to get an analytical solution, to make unrealistic hypotheses (for example perfect air cycles for internal combustion engines which students know to be far too simple if one is interested in air pollution...). At the other extreme, in the industrial world, engineers and scientists have access to powerful computerized environments.

A tool like Thermoptim allows one to overcome this kind of problem and makes possible a revival of new educational methods in the field of thermodynamics.

A Club named Educational Software Tools for Applied Thermodynamics is being set up. Its objective is to gather together educators belonging to higher education institutions and universities who wish to promote the development of software tools in this field and the exchange of experience on the various ways that they can efficiently be put in practice.

The members of the Club can have preferential access to the tools included in the Thermoptim series. If you are a teacher and wish to get more information on this Club, please send an e-mail to the following address : thermoptim@cenerg.ensmp.fr