For weeks, the plant’s vacuum system had been underperforming. The steam ejector, meant to pull a vacuum on the main distillation column, was failing to reach its design critical back pressure. Elias had run every CFD simulation in the book, but the real-world results were stubbornly off by 15%.
Heavier gases are generally easier to entrain than light ones like Hydrogen. 2. Motive Fluid Parameters The motive fluid (usually steam) provides the energy.
Ensure your entrainment ratios align with the Heat Exchange Institute (HEI) curves for steam jet ejectors. ejector design calculation xls fixed
To build a robust calculation sheet, you must define the following input variables: A. Motive Fluid Properties Usually high-pressure steam or air. Temperature ( Tmcap T sub m ): Needed to determine specific volume. Flow Rate ( Wmcap W sub m ): The mass flow available to do the work. B. Suction Fluid Properties Suction Pressure ( Pscap P sub s ): The vacuum level you aim to maintain. Entrainment Ratio ( ): The ratio of suction gas to motive gas ( ). This is the most critical output of your calculation. C. Discharge Conditions Discharge Pressure ( Pdcap P sub d ): The pressure the ejector must overcome (back-pressure). 3. The Step-by-Step Calculation Process
(choked flow assumption)
where Q_s is the secondary fluid or gas flow rate, ρ_m is the mixture density, and v_m is the mixture velocity.
The spreadsheet never warns if the nozzle or diffuser is not choked. Fix: For weeks, the plant’s vacuum system had been
Whether you are designing a steam ejector for a vacuum drier, a gas ejector for a flare gas recovery system, or a liquid ejector for a chemical reactor, demand a fixed spreadsheet. Look for no iterative loops, no hidden macros, and a validation sheet. In the words of senior process engineers: "A fixed ejector XLS is worth a thousand simulations."
This guide explores the underlying principles and provides a practical framework for building or using an xls template to streamline the design of fixed ejectors, transforming a tedious manual process into a powerful, rapid calculation tool. Heavier gases are generally easier to entrain than