Smart Thermodynamic State Calculator: Ideal Gas

 |Intro| |Instructions| |Ex.1| |Ex.2|
Introduction:
Welcome to the Smart Thermodynamic Table: Ideal Gas page, part of the 'Utility Applets' library of TEST, The Expert System for Thermodynamics. TEST is a network of HTML pages with embedded Java Applets that helps users solve thermodynamic problems and perform parametric studies visually without any programming.

An Ideal gas can be simply defined as a gas (or liquid) that obeys the ideal gas equation p=rho.R.T. All gases under low pressure (compared to the critical pressure) and/or high temperature (about 250K or more) can usually be treated as ideal gases. Gases covered by the Ideal Gas Calculator include: Air, Nitrogen(N2), Oxygen(O2), Hidrogen (H2), Carbon-di-Oxide(CO2), Carbon-monoxide (CO), Argon(Ar), Neon(Ne), Helium(He), Methane(CH4), Ethane(C2H6), Ethylene (C2H4), Propane(C3H8), Butane (C4H10) and Steam(H2O).

The Smart Thermodynamic Table is more than a visual thermodynamic state calculator for Ideal gases. In this ideal gas table a state is visually presented (see the examples below) as a collection of variables (such as p, T, v, h, s etc.). A gas is chosen from a selection of gases and known variables are entered in any order and in any units (the applet checks for redundancy of inputs, converts units internally, provides balloon help and generates suitable warnings when appropriate) and a click on the 'Calculate' button evaluates the states partially or fully if sufficient information is known. The calculated states are auto-saved and can be plotted on a 'p-V', 'T-s' or other thermodynamic diagrams by choosing a plot-type from the diagram selector.

While evaluating a state related to another (say, isentropic states), algebraic expressions involving state variables can be used. For instance, to evaluate State-2, isentropic to State-1, one can enter s2 as '=s1'. Once a series of states are evaluated, updating all calculations for a change in any input variable is a snap. Simply change the value and click on the 'Super-Calculate' button. The smart table takes care of the rest making it an exciting visual design tool for the 'What-If' people. A more comprehensive introduction can be found in the Introduction/Tutorial page (linked at top) and is highly recommended for all users.

The examples below contain images of the ideal gas table in action. Once you get a rough idea about how the smart table works, you can start using the real thing by following these instructions.

 |Intro| |Instructions| |Ex.1| |Ex.2|
Instructions:
There are two ways of doing anything, the quick way and the right way.

If you are in a hurry, do the following: (a) Browse the examples below (takes only a minute), and (b) Launch the customized Java applet (called a daemon) by clicking the appropriate link at the top of this page. If you have a modern browser (Netscape 4.5 or better, Microsoft IE 4.0 or better), the daemon will appear in about 10-50 seconds (1 second if you are running from a locally installed TEST) and you can start exploring.

To fully exploit TEST follow thest steps: (a) Start the Introduction/Turorial for the Expert System by clicking the link at the top of this page. (b) Explore a few daemons as explained in the tutorial. (c) Browse a few topics of your choice from the Slide Show. (d) Once you understand the algorithm TEST applies for locating the right daemon for a given problem, you can use the TEST-Map to quickly launch a desired daemon. Of course, all these may take better part of an hour - but, trust me, you will not regret it.

 |Intro| |Instructions| |Ex.1| |Ex.2|
Examples:

Example-1: The air in an automobile tire with a volume of 18 ft3 is at 90oF and 25 psig. Determine the amount of air to be added to bring the pressure up to 30 psig. Assume the atmospheric pressure to be 14.7 psia and the temperature and volume to remain constant.

Solution: To bring up the appropriate daemon (applet) navigate to TEST Home Page, Test, Daemons, States, and Ideal Gas in sequence (or directly using the 'Smart Ideal Gas Applet' link at the top).

The daemon page will be displayed on the upper frame and a help page will appear on the lower frame of the browser window. As the daemon gets loaded, you may see its shadow for about 5-15 seconds.

 Fig. 1. Image of the Smart Table (Ideal Gas Daemon) producing solution to Example 1.

Choose the working fluid (air is the default gas), air, from the fluid selector. Enter the values of the known variables, volume of the tire, temperature and pressure (note the use of equation), and click the 'Calculate' button to obtain the complete state. All the properties have a suffix '0' as the state is identified as 'State-0'. Note that mass is only one of the unknown variables calculated by the daemon to give a complete picture of the state. The Ideal gas table offers many other smart features like this, some of which are highlighted in the slide show (link at the top margin) and some are left for the users to explore.  Fig. 2. Image of the Smart Table (Ideal Gas Daemon) completing solution to Example 1.

Choose 'State-1' from the state selector, enter the new pressure, temperature and volume, and 'Calculate' the new mass.

 |Intro| |Instructions| |Ex.1| |Ex.2|

Example-2: How would the answer in Ex. 1 change if the temperature is 30oF instead?

Solution: After Example 1 has been solved, simply change the temperature in 'State-0', click the 'Calculate' button to register the change and 'Super-Calculate' button to update all calculations. The simplicity of performing a parametric study is the real strength of the Smart Ideal Gas Table.   Fig. 2. Image of the Smart Thermodynamic Table (Ideal Gas Daemon) producing solution to Example 2.

These examples are only meant to give the reader the flavor of a daemon (applet). Many more examples of solved problems, grouped into fifteen different chapters, can be found under TEST Home Page> TEST> Problems page. Before you start using this particular applet, it is strongly recommended that you take a look at the 'Slide Show' to get a feel for the breadth of thermodynamic topics TEST covers. Besides more examples and a visual tour, you will also find a visual manual for the daemons explaining different buttons and widgets found in the daemons. You will see how a wide range of thermodynamic problems can be visually solved and parametrically studied without the need for a single line of programming.

 |Intro| |Instructions| |Ex.1| |Ex.2|