An ejector (or eductor) uses a high-pressure motive fluid to entrain and compress a low-pressure suction fluid. Designing an efficient system requires precise calculations of mass flow rates, pressure drops, and nozzle geometry.
Converts the pressure energy of the motive fluid into high-velocity kinetic energy.
Easy to share with team members and include in technical dossiers. Core Components of Ejector Design Calculations
If your XLS sheet calculates a motive steam usage that varies by more than
): Use established correlations like those from Al-Dessouky et al. which use constants (A through J) to relate pressures and expansion ratios. ejector design calculation xls fixed
At=mmPm⋅R⋅Tmγ⋅M⋅(2γ+1)γ+1γ−1cap A sub t equals the fraction with numerator m sub m and denominator cap P sub m end-fraction center dot the square root of the fraction with numerator cap R center dot cap T sub m and denominator gamma center dot cap M center dot open paren the fraction with numerator 2 and denominator gamma plus 1 end-fraction close paren raised to the the fraction with numerator gamma plus 1 and denominator gamma minus 1 end-fraction power end-fraction end-root is the universal gas constant and is the molecular weight. Step 4: Size the Diffuser Throat ( Adcap A sub d
Designing an ejector involves calculating the dimensions of its key components based on thermodynamic and fluid dynamic principles to achieve a desired performance, primarily the entrainment ratio Key Components of an Ejector A standard ejector consists of six main parts: Steam Chest: The inlet for the primary (motive) fluid. Primary Nozzle:
, use iterative calculations to find the optimum geometry for a given set of operating conditions. Literature Guides: Authoritative texts like Steam Jet Ejectors for the Process Industries ASME Digital Collection
) of the motive steam exiting the nozzle throat and tip is calculated using the enthalpy drop during isentropic expansion: An ejector (or eductor) uses a high-pressure motive
For a standard steam jet ejector, a common empirical correlation used in Excel-based models to find the Entrainment Ratio (
A robust ejector calculation spreadsheet should be structured with clearly defined input, calculation, and output sections. A. Input Data Section
The high-velocity jet creates a localized vacuum, drawing in the suction fluid and mixing the two streams.
Go to File > Options > Formulas → Disable "Enable iterative calculation". This stops the #VALUE! crashes. Easy to share with team members and include
, specific constants (A through J) are used in empirical correlations to determine Non-Choked Flow: For compression ratios is less than 1.8 , a different set of constants is applied. Motive Mass Flow Rate: For a fixed nozzle, the mass flow rate (
Finally, a fixed XLS includes a locked "Report" tab that formats all results (throat diameter, mixing length, predicted backpressure, entrainment ratio) into a single-page summary. No cells in this tab are editable, guaranteeing that printed designs are traceable.
Ejectors, also known as jet pumps or ejector pumps, are devices that use a high-pressure fluid or gas to create a low-pressure area, which in turn induces the flow of a secondary fluid or gas. The design of an ejector involves several key parameters, including:
The mixing chamber design parameters are calculated using the following equations: