a. Equilibrium daemons: Many equilibrium problems involving isolated systems can be solved by various daemons by maximizing entropy as illustrated in the examples section.

However, for chemical equlibrium at a given pressure and temperature, the Gibb's function must be minimized to determine the equilibrium composition. TEST equlibrium daemons are built on this principle. If you are familiar with the equilibrium program STANJAN, then you can learn to use these daemons in minutes.

The equilibrium daemons are available both for closed processes and open steady devices. The equilibrium temperature of a combustion reaction in a closed system or a steady state reactor can be calculated quite easily with these daemons. At present these daemons handle only gas mixtures, not just for combustion reactions, but any type of reactions.

In most equilibrium analysis, the composition of the reactants is assumed given. As you launch the equilibrium daemon, the composition panel (see Fig. 1 below) is displayed by default. Work on the Reactants block first. Select the Reactants by simply clicking on the respective checkboxes. You can change the default proportion of 1 kg by clicking on the amount and changing it (either mass or moles). To delete a species from the selected list, simply uncheck it.

Suppose methane and 20% excess air are the reactants. Then you can use any of the non-premixed (separated) combustion daemon to balance the reaction (or do it manually) and then enter the moles of methane (1 kmol), oxygen (2.4 kmol), and nitrogen(9.03 kmol). Note that the mass and mole fractions are calculated on the fly as you change the reactant amount. Also, each reactants are included in the product list automatically. You can select as many species in the product list as you want by simply clicking the selection checkbox (in this case we selected CO2, H2O, CO, NO, NO2 and OH). Finding the amount of each species is one of the goals of equilibrium calculations.

Once the reactants mixture is specified, its state can be found by entering known properties such as temperature and pressure in the state panel. Make sure that the Reactant radio button is selected for that. For a total mass flow rate of 1 kg/s, the reactants state is shown in Fig. 2 for 100 kPa, 25 deg-C.

Now suppose the products are leaving at 1500 deg-C, 100 kPa. For the products state, State-2, enter p2=p1 and T2, select the Products radio button and Calculate the state.

Browse the Example section for a number of solved examples.

With the reactants and products state obtained, a device analysis can be carried out just like any other single-flow daemon to calculate the heat transfer (see Fig. 5). Note that for a closed process, a similar analysis can be performed.

Browse the Example section for a number of solved examples.