you do not see aat the bottom of
this page, click here
to go to the parent page and click on R-22.)
Thermodynamic State Calculator: Refrigerant-22
Welcome to the Smart Thermodynamic
software module, part of the 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.
The Smart Thermodynamic Table is more than a visual
thermodynamic state calculator for refrigerant-22. In this R-22 table
a state is visually presented (see the examples below) as a collection
of variables (such as p, T, v, h, s etc.). Known variables 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).
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
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
, making TEST an exciting visual design tool for the What-If
A more comprehensive introduction can be found
in the Tutorial page and is highly recommended for all users.
The examples below contain images of the R-22 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 from a TEST-CD) and you
can start exploring.
To fully exploit TEST follow these steps: (a)
Browse the Slide Show (at least the first 20-30 slides); (b) Start the
Tutorial and get a hands-on training on your favorite daemon (do not forget
to read both the Theory and Practice pages). (c) Explore a few daemons
systematically as explained in the tutorial. (e) Once you understand the
TEST algorithm, you can use the TEST-Map to quick-start a desired daemon.
(f) If you like using the software, please register (from the Home page)
as a courtesy. (g) For better speed and service, acquire a TEST-CD or a
site license. Of course, all these may take better part of an hour - but,
trust me, you will not regret it.
Examples : (The
working fluid used in the solutions may be different from R-22, but the
procedures remains the same.)
the enthalpy of liquid R-22 (Refrigerant-22) 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, Test,
Daemons, States, and R-22 in sequence (or directly using the 'R-22
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 about 4 reasons
for that. (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. Instructions for
how to rectify the first three problems can be found in the Help section.
For the last two problems, you need a TEST-CD. A TEST-CD will give you
native performance with virtually no wait time for loading pages (applets
takes a couple of seconds at most as opposed to minutes over the net).
|Fig. 1. Image of the Smart Table (R-22
Daemon) producing solution to Example 1.
Taking advantage of a classical
simplification, a Liquid can be treated as saturated liquid (at the same
temperature) within acceptable errors. 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
identified as 'State-1'.
|Fig. 2. Image of the Smart Table (R-22
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 refrigerant-22 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 Tutorial section.
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 R-22 smart table. 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 (R-22 Daemon) producing solution to Example 2.
These examples are only meant to give the reader
the flavor of a daemon (applet). For a systematic exploration of TEST,
start with the Slide Show, then the Tutorial and then start solving problems.