Welcome to the Smart Thermodynamic Table: Real 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.

A real gas can be simply defined as a gas (or liquid) that obeys the compressibility equation p=Z.rho.R.T. (For Z=1, the gas is called an ideal gas). All gases under high pressure (about 100 atm or more) and/or low temperature (about 200K or less) should be treated as real gases. Gases covered by the Real Gas Calculator include: Nitrogen(N2), Oxygen(O2), Carbon-di-Oxide(CO2), Argon(Ar), Neon(Ne), Helium(He), Methane(CH4), Ethane(C2H6), Propane(C3H8), Steam(H2O) and Refrigerant-12(R-12).

The Smart Thermodynamic Table is more than a visual thermodynamic state calculator for real gases. In this real 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 (including the phase composition of the real gas) 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 real 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.

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.

 

Example-1: A 10 gallon tank contains 9 gallon liquid propane and the rest vapor at room temperature (30oC). Calculate the pressure inside.  Solution: To bring up the appropriate daemon (applet) navigate to TEST Home Page, Test, Daemons, States, and Real Gas in sequence (or directly using the 'Smart Real 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.  Trouble Shooting: If the daemon (as pictured below) does not show up even after a minute, may be your browser is unable to run Java applications. I know of three reasons for this. (i) Your browser has not been updated since the Jurassic age, (ii) Java is turned off, (iii) Security is set to 'high' (in case of Internet Explorer). Because TEST takes advantage of JDK 1.2 (the latest Java revision), you will need Internet Explorer 4.0 or Netscape 4.5 (not 4.05) to run TEST effectively. If you do not want to update your browser, you can still use TEST-2.01, a relatively primitive version. Instructions for how to rectify these problems and links to download the latest version of the browsers (Navigator or Explorer) can be found in the Troubleshooting/FAQ file on the TEST Home Page. If the daemon looks 'broken' (happens occasionally with Explorer 4.0) close (not exit) and open the browser to refresh the display.  Fig. 1. Image of the Smart Table (Real Gas Daemon) producing solution to Example 1. Choose the working fluid, C3H8, from the fluid selector. Enter the values of the known variables, volume of the tank, temperature and volume fraction of the vapor (Velocity and height z are set to 0 by default), and click the 'Calculate' button to obtain the complete state. It is that simple. All the properties have a suffix '0' as the state is identified as 'State-0'. Note the use of volume fraction y as a property just like the quality x. Without this property the solution of this problem would be much more difficult. The real 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.

 

Example-2: How would the answer in Ex. 1 change if the working fluid is ethane (C2H6) instead? Solution: After Example 1 has been solved, simply choose the new real gas from the fluid selector. You are done. The simplicity of performing a parametric study is the real strength of the Smart Real Gas Table.  Fig. 2. Image of the Smart Thermodynamic Table (Real Gas Daemon) producing solution to first part of 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.