A. Welcome to TEST - The Expert System for Thermodynamics! This hands-on tutorial will introduce you to some of the core features of TEST. If you do not like tutorials, we recommend that you browse at least the Getting Started and My First TEST Solution sections linked from the Tutorial home page. Beside this tutorial, there are two other resources, Visual Tour and Examples, that can help you master TEST.

TEST is a one-of-a-kind webware for learning, teaching, and practicing thermodynamics. It covers the entire range of topics taught in a typical engineering thermodynamics class - from property evaluation through steam power, psychrometry, chemical equilibrium and gas dynamics.

TEST is a visual platform where you can look up traditional charts and tables (try Map>Tables&Charts) , visualize thermodynamic principles and systems through animations (try Animations link), browse fifteen chapters of examples (with manual and TEST solutions) and problems (manual solutions accessible to approved users), and summon up the daemons - the embedded thermodynamic calculators (java applets) which can help you solve even the most complicated thermodynamic problem visually. Once a problem is solved, states can be plotted on thermodynamic diagrams, a solution report can be generated, and the solution can be shared with other users through generated TEST-codes. More importantly, since all variables are visually exposed, any combination of input parameters can be changed and any number of what-if scenarios can be pursued by clicking a single button.

Created with web-friendly tools, TEST is platform independent (Windows, MacOS, Unix), browser independent (Firefox, IE, Safari, Opera), can be locally installed for speed, or accessed over the Internet.

Although TEST is perpetually under construction, several articles have been written about it, a book introducing TEST has been published by Prentice Hall , and a textbook that integrates TEST with the traditional approach is nearing completion (expected publication date: Dec. 2008). The biggest success of TEST, however, is its expanding user base - more than 2000 educators, 10000 students and 3000 professionals have registered  to use TEST.  Translated into Spanish and Japanese, the complete web site is mirrored in more than ten countries, and hundreds of educators from 52 countries have installed TEST locally for use in their classrooms.

The reward for working on the TEST project comes from some of the "thank you" letters I receive from users from all over the world (some of those are posted on Comments section at the bottom of the Tutorial page), and knowing that this work is benefiting so many. Whatever fund is raised from licensing fees is put right back into the TEST project .

D. TEST Solution Briefly here is how TEST works. A problem solving session begins with the most general system - an open, unsteady system. You start to simplify the system by selecting an appropriate branch (open vs. closed, for instance) that best describes the problem from an exhaustive list of choices offered by a series of simplification  tables. As more specificity is added to the system (steady vs. unsteady,  for instance), the changes in the system (shown by an animation) and governing equations (mass, energy, and entropy balance equations) are displayed. Finally, you are asked to select a material model (ideal gas vs. phase-change model, for instance) for the working substance. At that point,  a daemon (see Fig. 1 above), aware of the material properties of the working substance and the governing equations for this particular system, is launched. (Takes about 10-60 seconds over the Internet and less than 5 seconds when locally installed).   

Use of Microsoft Excel type algebraic expressions makes it easy to construct related states. For instance, entropy for state-2, isentropic to state-1, can be entered as '=s1'. Standard algebraic functions can be used in such expressions.

The calculated states are then imported into the problem specific device or process panels as inlet, exit, beginning, or finish states - the anchor states - for a device or a process. The known device (or process) variables such as heat and work transfer are then entered. As the Calculate button is clicked, the mass, energy and entropy balance equations, displayed in their customized form in the device (or process) panel, are solved, information is passed back to the state panels and all the states are updated, completing the energy and entropy analysis. A separate panel is used for exergy analysis.  In the analysis of cycles, multiple devices (or processes) are imported into the cycle panel, where the cycle variables are calculated from the constituent device (or process) panels.

But the fun begins after you solve a problem. Because all the variables are visually exposed, you can study any conceivable what-if scenario by simply changing one or more variables and updating all calculations by a single click (as in a spreadsheet). A simple problem of finding the mass of water vapor in a room can be converted to a humidifier design exercise by studying the water requirement to achieve a desired relative humidity. A study of how condenser pressure affects the thermal efficiency of a Rankine cycle can be instantly turned around to see the effect of boiler pressure, or the turbine efficiency, or the maximum temperature - all without a single line of programming. 

TEST produces a complete solution rather than a narrow answer (for instance, in a problem to determine exit velocity in a nozzle, the nozzle exit area is also calculated), providing insight to a problem. With the click of a button the visual solution generates detailed printer-friendly output, spreadsheet-friendly property table and a set of instructions called TEST-codes that can be used  to jump-start the visual solution. Using TEST-codes students can collaborate on a solution  remotely by emailing partial solutions to each other.

1. The Unit Converter and the DeskCal scientific calculators are good daemons to start with. The DeskCal appears in a floating window and can be used even after the TEST window is closed. It uses the familiar syntax of Microsoft Excel equations (Sin(30), ln(2+4*5^3), etc.), and you can scroll, cut and paste expressions - features that your calculator probably lacks. Try 0/1 or, better, 0/0. (By the way, NAN stands for Not a Number).

2. The VT module of TEST contains hundreds of animations and pedagogic discussions to explain theoretical concepts and how thermodynamic systems work. For instance, you may find Anims. 1.F.zerothLaw and 2.C.energyBalanceEqn (to locate an animation go to VT, select the chapter, the section, and then the particular animation) insightful while learning about the zeroth law and the first law of thermodynamics. Similarly, while studying turbine, you can visualize the effect of an increase of the inlet temperature or pressure by simply selecting the appropriate radio button in Anim. 4.A.turbine. The organization of the animations are keyed to the textbook being written by Bhattacharjee. Browsing animations on a topic before it is discussed in the class can greatly prepare you to follow a lecture.

3. Learning to evaluate thermodynamic properties accurately is the key to thermodynamic problem solving. You will find tables and charts in Daemons>Basics>Tables page and the state calculators in the Daemons>States>System page. In the TEST approach, you must select a material model to get to the table or daemon. By forcing you to select a model first, silly mistakes such as using pv=RT (IG model) for a PC (phase change) fluid can be averted. While seeking a property, ask "what model am I going to use" rather than "what formula or what table should I use". The right model will always lead you to the right formula or the right table.

4. Browse the property tables organized according to the underlying material models in Daemons>Basics>Tables page. You may find these tables friendlier than the static tables in the back of your textbook.

5. While evaluating a property from a table, use the corresponding state daemon to verify your answer. Not only will it help you catch silly mistakes, you will also improve your skill for interpolation through quick eye estimates.

6. When you evaluate a property using a state daemon, the entire state, consisting of material, thermodynamic, extrinsic, and even some system properties, are evaluated at once. With this wholesome approach, you can learn about groups of properties and how they are related. You can use the state daemons to explore how properties such as v, u, s, depend on easily measurable properties p and T for different working substances.

7. After you evaluate a state, try one of the standard thermodynamic plot (T-s, p-v, etc.). You can draw constant property lines on these plots and gain a deeper understanding of the relationship among thermodynamic properties for different material models.

8. Start solving a system problem starting at the Daemons>Systems page. As you simplify the problem (closed vs. open systems, steady vs. unsteady, etc.) watch how the system animation and governing equations simplify. The final system daemons also display the customized mass, energy, and entropy equations in its device or process panel. Verify your manual solution with the output of the TEST solution.

9. Once you obtain a TEST solution for a system problem, you can perform what-if (parametric) studies for further insight. For instance, after obtaining the power produced by a steam turbine, you can change the inlet temperature and see how it affects the output. Such studies are at the heart of thermal system design.

10. A complex problem such as a combined power cycle or a cascading refrigeration problem may involve tens of state and device calculations. The solution can be saved at any stage by generating solution macros called TEST-codes. TEST-codes can be saved as a text file and used at a later session to recreate the solution. TEST-codes can also be shared in group collaboration.

11. While solving a problem from your textbook find a similar problem from the Problems page. The animation and TEST-codes that accompany most problems can be quite useful in guiding you through the solution.

12. Got a technical question or a comment? Please write to the author directly at support@thermofluids.net.