EQS – Equation Solver

Type the equations of an engineering problem in any order. EQS solves them, with fluid properties, units checked in every equation, parametric tables and plots.

Free download with a 14-day trial · Mac, Windows and Linux · No account, works offline

EQS: equations of an organic Rankine cycle and their solution with units

Made for engineering courses and engineering work

Thermodynamics, heat transfer, fluid mechanics and energy systems, from the first homework to the design calculation.

Equations in any order

Write the equations as on paper. EQS finds which unknown each equation gives and solves the equations together where they must be.

Units checked

Every number has its unit, and EQS checks each equation. See SI and English units side by side.

Fluid properties

Water, steam, refrigerants, air, gases and mixtures, brines and incompressible liquids, from the open CoolProp library.

Tables and plots

Change one input over a range and see every result. Plot curves, zoom, fit curves, and export to SVG and PNG.

Property diagrams

T-s, P-h, h-s and more, with the states of your cycle drawn on them. The psychrometric chart for humid air.

Cycles as flowsheets

Draw pumps, turbines, heaters and condensers. EQS writes the equations and shows the stream table and the energy balance.

Analysis

Optimisation, uncertainty and sensitivity, and integration in time.

Learn by example

More than 40 worked examples and a built-in guide that teaches EQS step by step.

See EQS at work

All pictures show the real program with the examples that come with it.

A Rankine cycle on the T-s diagram of water.

A parametric table with two plots — Change the boiler pressure; see the efficiency and the turbine exit quality.

The flowsheet window with stream table and energy balance — A cycle drawn as a flowsheet, with its stream table and energy balance.

Humid air mixing on the psychrometric chart — Mixing two humid air streams, on the psychrometric chart.

Formatted equations of a regenerative Rankine cycle — Equations formatted as in a textbook; copy them as LaTeX or as a picture.

Pricing

Try everything free for 14 days. Then buy once; updates stay free.

Mac

€22

one purchase, VAT included · US$19 in the United States · free 14-day trial

From the Mac App Store, with your Apple Account
Apple silicon and Intel Macs, macOS 12 or later
On every Mac where you use the same Apple Account

Buy on the Mac App Store

Universities

Site licence

one faculty or department · per year

Every computer of the laboratories, and the students' and staff's own computers
Windows, macOS and Linux; installers for the laboratories
One licence file, installed once a year, no internet needed

Ask for an offer

Windows and Linux

Licence

for one person

The same EQS as on the Mac
Windows 10 and 11, and current Linux distributions
A trial licence on request

Questions

Do I need an account or an internet connection?

No. EQS runs on your computer, and your models stay in your own files. The Mac App Store version makes no connection of its own.

What can I do without buying?

Open and read every model and example at any time. The free 14-day trial solves without limits. After it, a purchase or a licence file unlocks solving again.

My university has a licence. Does it work on my Mac?

Yes. In EQS, open Help → License Status… → Install License File…, and choose the licence file from your university.

Which fluids and data does EQS have?

The fluids of the open CoolProp library (water and steam, refrigerants, air, gases and their mixtures, brines), humid air, ideal-gas data for combustion, and property tables of common solids.

Where do I get help?

Help → EQS Guide in the program, and the support page.