based on empirical curves or the . This correlation uses correction factors for molecular weight and temperature:
To construct your spreadsheet cells, apply this structured reference layout for your formulas: Excel Formula Template Engineering Description =SQRT(Gamma * (8314 / MW) * Temp) Speed of sound in the fluid medium. Nozzle Throat Area mm2m m squared =(MotiveFlow / (3600 * ThroatDensity * SonicVel)) * 10^6 Minimum cross-sectional area of nozzle. Expansion Ratio =MotivePressure / SuctionPressure Pressure drop driving force across nozzle. Entrainment Ratio =VLOOKUP(ExpansionRatio, HEI_Table, 2, TRUE) Suction capacity per unit of motive fluid. 5. Troubleshooting & Validation Tips
Motive Fluid (High Pressure) │ ▼ ┌───────────────┐ ───────┘ Motiv Nozzle └──────────────┐ Suction ├──────► Discharge (Mixed Fluid) Fluid ┌───────────────┐ │ ───────┐└───────────────┘ Diffuser │ └──────────────────────────────┘ An ejector consists of three primary mechanical sections:
An Excel spreadsheet for ejector design is an invaluable tool for process and mechanical engineers, offering a powerful combination of theory, calculation speed, and flexibility. By mastering the 1-D thermodynamic model and implementing it in Excel, you can perform accurate preliminary designs, conduct sensitivity analyses, and optimize ejectors for a wide range of applications.
: Transvac Engineers offers online software for preliminary ejector screening that mimics these XLS calculations. ejector design calculation xls
The XLS file accompanying this paper includes full formulas, validation cases, and charting macros.
rc=(2γ+1)γγ−1r sub c equals open paren the fraction with numerator 2 and denominator gamma plus 1 end-fraction close paren raised to the the fraction with numerator gamma and denominator gamma minus 1 end-fraction power Step 3: Nozzle Geometry Calculation Rearrange the choked flow equation to solve for area. Nozzle Throat Diameter ( Dtncap D sub t n end-sub ):
Almost all spreadsheet-based ejector design calculations are founded on a . This model simplifies the complex, 3D, turbulent, and often supersonic flow inside an ejector into a set of algebraic equations. The "1-D" assumption means that flow properties (pressure, temperature, velocity) are considered uniform across any cross-section and only vary along the ejector's axis.
Steam ejector (El-Dessouky et al., 2002) based on empirical curves or the
What you plan to use (e.g., steam, air, or hydrocarbon vapor).
Before diving into the calculations, let's review the basic components of an ejector:
Remove 200 kg/h of air (suction) from a vacuum column at 0.3 bar abs, compressing to 1.2 bar abs, using 8 bar g steam.
If you do not have access to Steam Table functions in Excel, you can use the empirical curves converted into formulas. 1. Fundamental Principles of Ejector Operation
[ R = \fracW_suctionW_motive ] Used to determine ejector type (single-stage, multi-stage).
The high-pressure motive fluid enters the converging-diverging nozzle, expanding to a supersonic velocity (
First, calculate the Target Entrainment Ratio: [ Er = \frac\dotm_s\dotm_p = \frac100 \text kg/h500 \text kg/h = 0.2 ]
Designing or troubleshooting an ejector requires precise aerodynamic and thermodynamic equations. Engineers rely heavily on specialized Excel spreadsheets to automate these complex iterations. This article provides a comprehensive deep dive into the engineering principles of ejector design and outlines how to construct a robust tool. 1. Fundamental Principles of Ejector Operation