EES user

[Lc_shi]

HI Sir
Who have used EES ?
I've a demo rev and find it's a really good one,but it's not cheap--1000USD. I want to get some advice from who used it and how about the benefit you can get from it? Then I'll make decision-


regards
LC

[Erik Detroit]

I've been using EES since college days in 1994. The thermophysical properties functions enable very quick and easy writing of refrigeration cycle mathematical models. It also has very good iterative solving capabilties and calculations are very fast. I am a big fan of this software.

[Lc_shi]

Hi Erik
You mean you've been using this software since 1994. You should be very familiar wiht it. Could you tell me some real cases in your work? thx

rgds
LC-

[US Iceman]

Hi LC,

I have been using EES since the early 1990's also. I continue to use it daily in my work. An example of it's capability is to solve the Colebrook equation for friction factors with no problem.

The thermophysical properties are a big reason to use EES. You can simply insert a reference for the specific property you need (specific volume, enthalpy, speed of sound, etc) into your worksheet. The input values can be temperature, pressure, quality, etc.

Very useful to someone who works on refrigeration or air conditioning all of the time. It also has additional capabilities for various glycol properties, air-water functions, steam, etc.

You can create parametric tables and solve for various values to see the relationships of the equations also.

The program also allows you to write software functions such as loops, functions, IF-Then-Else statements. Just about anything you can do in C or Visual Basic you can do in EES.

You can also link other programs such as Excel to EES.

One of the professors who developed this program also worked on the NIST RefProp program for high accuracy refrigerant properties.

In the past I used MathCAD and Excel for everything. Now, I only use EES and Excel.

I would recommend the professional version of the software. It does take some time to become familiar with the program, but once you begin to get comfortable with this program you will be surprised at how much you use it.

I'm currently working on a CO2 project with EES where we are trying to operate just above the triple point.

[Erik Detroit]

LC,
I use the software mostly to perform system modeling calculations, and to solve quick calculations involving refrigerants, psychrometrics, coolants, etc.

An example might be to quickly calculate the cooling capacity required if I know everything happening on the airside of an evaporator (flow rate air, temperature in, temp out, RH in, RH out).

Of course you can just pick up a psychrometric chart and roughly work this out, but the EES functions are very easy, and I make fewer mistakes (like the eye does not follow the correct line).

I also use it to answer theoretical questions. For example: How much power could be extracted from a CO2 expander to recover the throttling losses? How much power would be saved by using a two stage compressor with intercooling? Which refrigerant would have the highest COP for a particular situation? If you combined an air cycle machine with a vapor compression machine, how much condensate would be recovered, what would the overall COP be? For these types of questions, I write models and then create large parametric tables, and vary all of the variables to arrive at the optimums or answers.

For me, the syntax of the equations is very easy and logical, similar to excel, similar to how you'd write equations on paper. It's faster for me to perform a calculation even with writing the model in EES than on paper.

I use the commercial version, and I sometimes think the professional version might be nice for editing equations, but for how I use the software It's not worth it to me.

Regards,
Erik

[US Iceman]

LC,

Here is an example of the syntax: The first line is the comments for the variable. I find it it very useful to write some comments for each varaible, or the calculation. This helps to follow your work in logical steps and also helps with debugging the code/model being developed.

The second line is the actual syntax for for finding the vapor enthalpy of CO2 at some pressure.

" vapor enthalpy at evaporation pressure"
h_g=ENTHALPY(R744,P=P_controlled,x=1)

One thing you do have to watch is the use of parentheses in your equations. You can override the mathematical operator precedence by using parentheses, so you need to be careful with this.

It is the same problem you will find in Excel.

If you do a lot of work with refrigerants or psychrometric charts it is a big asset to have.

I believe you would find this very helpful with your work.

[Lc_shi]

Hi Erik,Iceman
Thanks for your input. I'll spend some time to review the EES demo and get more details.
How about the software upgrade ? is it free?

regards
LC

[US Iceman]

How about the software upgrade ? is it free?

For the first year you have access to program updates. See below quote from the EES website.

EES is an unusual program in that it is under continuous development. New versions appear frequently - often daily. The new versions fix bugs in older versions and add new capabilities. With Instant Update Service, users can download a new version from our server whenever they wish to update. The cost for this service is 20% of current cost of the program per year. (The update cost will be 40% of the current cost for EES versions if you have not updated within the last two years).