Thermodynamic State Calculator: Refrigerant R-134a (H2FC-CF3 )
Welcome to the The Expert System for Thermodynamics (TEST) : H2FC-CF3
module of the thermodynamic property tables (calculators) to evaluate states and properties of hundreds of working substances. 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.
The Smart Thermodynamic Table is more than a visual
thermodynamic state calculator for H2FC-CF3 . In this refrigerant (H2FC-CF3 ) property table,
a state is visually presented (see the examples below) as a collection
of properties (such as p, T, v, h, s etc.). Known properties are entered
in any order and in any units (see Fig. 3) and a click on the Calculate button evaluates the states partially or fully (including phase composition)
if sufficient information is entered. The calculated states are auto-saved
and can be plotted on a p-V,
other thermodynamic diagrams by choosing a plot-type from the diagram selector
(see Fig. 2). The solution can be saved or shared through TEST-codes, which are generated when the Super-Calculate button is pressed.
While evaluating two related states (say, two
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
(see Fig. 4) button. In addition to update all calculations, a printer-friendly
output is generated on the Output window of the daemon (see Fig. 2).
Because all the State variables are exposed,
changing one or more input variables and evaluating their effects is really
a matter of two clicks (Calculate and Super-Calculate)
, making TEST an exciting visual design tool for the what-if
people. The working fluid as well as the material model (ideal gas vs. phase-change model, for instance) used can be changed without much effort.
A more comprehensive introduction can be found
in the Tutorial page which is highly recommended for all users.
The examples below contain images of the H2FC-CF3 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 (beginning TEST 7.5, registration is required for all users). If you have a modern browser (Netscape 6.1 or better, Microsoft
IE 6.0 or better), the daemon will appear in about 10-50 seconds (1-5 second
if locally installed from a TEST-CD). (c) Begin exploring (a tour of the Tutorial/Slide Show is strongly recommended even for those who hate manuals).
To fully exploit TEST follow these steps: (a)
Browse the Slide Show (at least the first 20-30 slides); (b) Read the Introduction and Navigation sections of the Tutorial. (c) Explore a few daemons
systematically as explained in the Tutorial. (d) Browse the Problems page to see what kind of problems these thermodynamic calculators can help you solve. (e) Browse the VT (Virtual Thermo) animations to see how thermodynamic systems work. (f) Once you master the
TEST approach (you will love it or hate it, no in between!), you can use the TEST-Map to quick-start a desired daemon.
Examples : (The
working fluid used in the solutions may be different from H2FC-CF3 , but the
procedures remains the same.)
the enthalpy of liquid H2FC-CF3 (H2FC-CF3 ) at a temperature of 20oC.
What is the final phase composition (quality) and pressure if the refrigerant
is throttled (at constant enthalpy) to produce a temperature of 0oC?
bring up the appropriate daemon (applet) navigate to TEST Home Page, Daemons, States, Volume, and H2FC-CF3 in sequence (or directly using the 'H2FC-CF3
Applet' link at the top).
The daemon page will be displayed in about 30-60 seconds (the more you use these calculators the faster the access speed becomes due to cashing by modern browsers). You may open a separate window and browse the Tutorial while waiting for the daemon to load in the other window.
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. There may be several reasons: (i) Your browser has not been updated since the Jurassic age
(you need Netscape 4.5+ or IE 4.0+), (ii) Java is turned off, (iii) Security
is set to 'high' (in case of Internet Explorer). (iv) Your computer is
behind a firewall that filters Java Applets. (v) The connection is too
poor for the demanding Java applications to be loaded. Most of these problems (except the access speed) can be remedied by downloading a new version (Window update or download from www.netscape.com) of a modern version of the browser, then download java from www.java.com (Sun's one click java installation), and Flash Player from www.macromedia.com. If you acquire a TEST-CD, speed is no longer a problem; also, you can install TEST on your notebook or desktop and work off line.
|Fig. 1. Image of the PC (phase-change) volume state daemon. Select R134a (H2FC-CF3 ) from the list.
Enter the values of the known variables,
temperature and quality (x=0 for saturated liquid) (Velocity and height
z are set to 0 by default), and click the 'Calculate' button to obtain
the complete state. All the properties have a suffix '1' as the state is labeled as 'State-1'.
|Fig. 2. Image of the Smart Table (H2FC-CF3
Daemon) producing solution to Example 1.
Now choose 'State-2' from the state
selector, enter the known temperature and enthalpy (note the use of algebraic
expression rather than absolute value), and click the 'Calculate' button
to obtain the complete state. Note that the phase composition is evaluated
as part of the solution. The H2FC-CF3 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. 3. Instructions for calculating a State.
More details can be found in the Slide Show and Tutorial pages.
would the answer in Ex. 1 change if the initial temperature is 50oC
Example 1 has been solved, simply change the temperature T1 in State-1
to 50 C, click the 'Calculate' button to register the change and then the
'Super-Calculate' button to update all calculations. The ease with which
a parametric study can be performed without any programming is one of the
many features of the H2FC-CF3 (Refrigerant R134a) property calculator. Some of these features are highlighted
in the slide show (link at the top margin) and some are left for the users
|Fig. 4. Image of the Smart Thermodynamic
Table (H2FC-CF3 Daemon) producing solution to Example 2.
Note: These examples are only meant to give the reader
the flavor of a daemon (applet). Go to the Problems pages to see the range of thermal systems problems that the TEST can help you solve. The property tables will be updated in the future to include thermal conductivity, viscosity, etc.