Step 3 Module for self-training to energy powered systems

The first two steps have allowed you, in twenty hours or so, except for reminders and supplements, to acquire a fairly comprehensive overview of the basics of energy conversion, but it is clear that they do not cover much for the whole subject. The third step opens a much wider scope of activities, so that you can define a work program to meet your aspirations, depending on your objectives and personal time you have, and on advice given by those who supervise you.

The third step will allow you:

• firstly to perform further studies in addressing issues more complex than those you have studied before, such as cycles involving gas whose humidity varies. Your knowledge in thermodynamics will allow you to start writing your own equations for your models. You will find a number of indications about this in the textbook (Gicquel, R. Energy Systems, CRC Press, 2011). You will also discover the potential of the external class mechanism , which allows a user to extend the potential of Thermoptim by designing his own components for modeling technologies not available in the core of the package ;

• secondly to put in practice by yourself the knowledge gained in the previous steps, exploring innovative cycles, conducting mini-projects alone or in groups, or even by conducting discussions on the prospects of technology.

This page is under construction and will be gradually modified to take into account digital resources available in the future.

The external classes are elements of Java code that allows users to customize their work environment by building their own components (processes, mixers and dividers) or their own substances. They facilitate the interoperability of the software with the outside world, especially with other applications developed in Java.

Once created, the external classes become part of Thermoptim screens as the elements of the core, and can be used to model complex energy systems. This limits the modeling work and allows users to enjoy the features of the Thermoptim environment, resulting in easier and safer modeling.

Diapason session S07En_ext "Introduction to the use and programming of external classes" will allow you to get started with this mechanism. Specific documents present more complex features, such as those that allow you to perform calculations on wet gases or for combustion.

Since its inception, Thermoptim has functions for calculating properties of moist gases and points, but these are generally used for particular calculations, decoupled from standard thermodynamic cycle calculations, such as for air conditioning treatment. It is for this reason that moist processes have no symbol in the diagram editor.

Since a number of thermodynamic cycles involve changes in the humidity of gases, it was unfortunate not to be able to model them easily Thermoptim. That is why functions for calculating Thermoptim properties of gases and wet points were made available from external classes. A document explains how to use them.

You can also directly study in Thermoptim, without writing code, summer or winter air conditioning cycles , using the screens dedicated to the wet mixtures.

The analysis of various technologies performance leads in a conventional manner to calculate their energy balance. When seeking to optimize a system, the establishment of their exergy balances is of great interest, as it quantifies the irreversibilities. Building an exergy balance poses no particular problem but needs to be done carefully otherwise errors can be committed. Various tools to conduct exergy balances are proposed in Section Exergy analysis : a methodological guide and a spreadsheet for simple systems, the use of productive structures for complex systems.

If you disregard the relatively complex theory that this method is based on (pinch method with distinction of component and systems irreversibilities), the Thermoptim optimization method is relatively easy to present and use.

Let us start by saying that this is a variant of the Linnhoff method applied to energy systems. The Linnhoff method is used when designing complex exchanger system with a great many streams, for chemical engineering applications for example.

To choose a powerful exchanger configuration, thermal integration methods appear to be the best. They also have the advantage of appealing to analysts' physics sense, whereas purely automatic methods requiring working by trial and error.

Liquid absorption cycles involve at least two fluids: a solvent and a solute (the coolant). While other couples are studied, the only ones used in practice for almost all applications are the two couples LiBr-H2O and H2O-NH3.

The main interest of the liquid absorption refrigeration cycles is that they require only low power compared to their counterparts in mechanical vapor compression (less than 1%). Using a three-temperature thermodynamic cycle, they allow direct use of medium or high temperature heat to produce cooling, requiring little or zero mechanical energy input. As such, their theoretically total efficiency in terms of primary energy is greater than that of vapor compression cycles.

The modeling of a LiBr-H2O cycle is proposed.

For the time being, as only a limited number of thematic pages and guidance pages for practical works have been translated, we suggest that you choose personal works in parts 4and 5 of the book Energy Systems .