ByHrishikesh Gadre

Email: hgadre1@lsu.edu

Session IIntroduction to EES

Department of Mechanical Engineering

Louisiana State University

Engineering Equation Solver Tutorials

Spring 2004

Session 1 Outline

What is EES

What EES can do for you

Getting started with EES

Solving a thermodynamics problem.

About Windows menu.

What is EES

Engineering Equation Solver.

Solves large sets of non-linear algebraic equations.

Built-in functions for thermodynamic and transport properties.

Highly popular software in teaching courses like

Thermodynamics, Heat Transfer and Fluid Mechanics.

What EES can do for you

Solve set of simultaneous algebraic equations

Can be used to solve differential and integral equations

Generate publication-quality plots.

Capable of doing linear and non-linear regression.

Check unit consistency, do optimization etc.

EES over other equation-solving programs

Automatically identifies and groups equations that must

be solved simultaneously.

Provides many built-in thermodynamic and mathematical

functions.

Also, allows user to enter his/her own functions

Getting started with EES

To get familiar with EES, let’s start with a simple example

Solve set of 3 equations with 3 variables simultaneously.

2 2 3

ln( )

1

x x z

x y z

y zx

Starting new program in EES

Start EES

Click File menu Click on New

Entering the equations…

You will get a blank equations window. Equations can be entered in the same manner as for any

word processor.

Formatted equations The entered equations can be seen in the normal mathematical format. For that, go to Windows menu, and click on Formatted Equations. You will see Formatted Equations window like this.

Solving those equations…

To solve these equations, go to Calculate menu and click on

Solve, or directly press F2.

Immediately, you will see

this window before the

solution window appears..

There are few things to

note about this window.

Mainly, it shows the number of blocks, into which it has

divided the total equations, it also shows the time taken for

the calculations.

Solution window

Here is the Solution window as it looks.

It also shows the current unit settings

And if there are any unit consistency or conversion

problems.

Tables… Now, we will see how Tables menu work in EES.

For that, we will consider first and third of our three equations.

The second equation is enclosed within {} brackets. So, it will not be considered while calculation, which is

reflected in Formatted Equation window.

Tables continued…

Go to Tables menu, select New Parametric Table

A dialog box as shown below appears, select all three

variables x,y,z on left, then click Add and then OK.

Then, you get a blank table like this.

Go to Tables menu and select Alter

Values.

The dialog box as shown appears.

Select ‘x’ in the left window. Input

the First Value as 1, then select Last

value option from drop down list

and enter 20 as the last value. Then

click Apply.

Solving the table

You can see column of x

filled with 10 values equally

spaced within 1 and 20.

Then go to Calculate menu

and click Solve Table.

Enter First run as 1 and Last

Run as 10 and it calculates

values for y and z according

to the two equations.

Plots

Go to Plots menu, click New Plot Window and select X-Y plot.

Select x as X-Axis and y as Y-Axis, and click OK.

Plots continued…

You will get a plot like this.

This plot plots the column y

against column x.

Seen on the right side is the

toolbar. With the Add text

button on it, we can add text

items on the plot.

Plot over plot

Go to Plots menu again and select Overlay Plot.

Choose x as X-Axis and z as Y-Axis and select Y2 (right

Y-scale) from drop-down list.

You get a overlay plot (both

plots in same window) as

shown.

Here you can also see the

example of adding text items

on the plot.

This completes the discussion of this problem.

A Thermodynamics problem

Example 2-2 from Thermodynamics, 6/e by Wark and

Richards.

A small race car (go-kart) has a mass of 200 pounds with

the rider and is powered by a 3-horsepower engine.

Estimate how long it would take the go-kart to reach a

speed of 40 miles per hour on a level racetrack. Assume

that all of the engine power can be available as

mechanical power to accelerate the go-kart.

Setting the units

Go to Option menu, select Unit System.

It shows the units currently being used by EES.

Make sure the correct units are set and then proceed to

solve the problem.

Equations…

The main equations would be like this:

Power=3 “hp”

m_car=200 “lbm”

V_2=40 “mph”

V_1=0 “mph”

DELTAKE_car=W_mech

DELTAKE_car=m_car*(V_2^2-V_1^2)/2*convert(lbm-

mph^2, ft-lbf)

W_mech=Power*DELTAt*convert(hp-s, ft-lbf)

Use of Convert function

The ‘Convert’ function provides unit conversion.

The format is convert(‘From’,‘To’), where From and To

are Unit designations.

E.g. a=convert(ft,in) will give a=12 as solution.

Formatted equations

This is how Formatted

Equations window will look

like.

Note, here in place of the

function convert, the actual

conversion factor is written.

Calculate-> Solve, will

solve these equations.

Variable information

If you want your final solutions to be displayed with unit,

you can go to Option menu and select Variable Info.

Enter the units manually in Units column.

Also, you can set different things like initial guess, lower and

upper limits and the display format of those variables.

Windows menu

The Windows menu in EES gives different windows

related with the problem.

The interesting point here is worth noting. The ‘Close

Window’ control merely hides the window and doesn’t

actually delete it. That means, a closed window can be

reopened any time by selecting it from Windows menu.

Explore different options available in the menu like Tile,

Cascade etc.

Equations Window

Equation window operates much like a word processor.

Comments are enclosed in braces {} or “ ”. Comments

within {} are not shown in Formatted Equations window

but those in “” are shown.

Equations may be entered in any order. EES will block

these equations and reorder them for efficient solution.

Formatted Equations window

This window displays the same equations as in Equations

window but in a mathematical format which is easy-to-

read.

Examples include DELTA is shown by the symbol

If you write a_1, it will be shown as

1a

Residual windows

The Residual window, gives relative and absolute residual

values.

In addition, it also indicates equation blocking and

calculation order used by EES.

Diagram window

This window has several functions.

Basically, it gives area to display graphics and text

relating to the problem, e.g. a schematic diagram to help

interpret the equations.

Secondly, it can also be used to provide convenient input

and output of data.

Buttons can be located on this window such as Calculate

button to initiate the calculations.

Diagram window continued…

This shows the diagram window for the problem discussed.

It shows example of how diagram window can be used for

input and output of information.

Recap

What we have learnt today.

What is EES, its capabilities and advantages.

Getting started with EES

Solving a thermodynamics problem.

About Windows menu.

Thank You

That’s all for today….

THANK YOU