By ensuring your spreadsheet distinguishes between these modes and correctly handles compressibility and area ratios, you can reliably predict the behavior of these elegant, motiveless machines.
Engineers often turn to Excel (XLS) for these calculations because the physics involves complex, iterative loops. A "fixed" calculation sheet is the "Holy Grail" for a process engineer. Designing an ejector requires balancing: ejector design calculation xls fixed
This section calculates the pressures, areas, and velocities. This logic assumes an ideal gas and isentropic flow (standard for first-pass design). Area Ratio ( cap A cap R Cr=PcPecap
For critical flow (choked) of steam: [ Dt = \sqrt\fracW_m0.0408 \times P_m ] In Excel (Dt in mm): = SQRT( W_m / (0.0408 * P_m) ) ejector design calculation xls fixed
When using a calculation spreadsheet or manual method, the following parameters are critical: Entrainment Ratio ( The ratio of the mass flow rate of the secondary fluid ( ) to the mass flow rate of the primary fluid ( Compression Ratio ( cap C cap R The ratio of discharge pressure to suction pressure. Area Ratio ( cap A cap R
Cr=PcPecap C r equals the fraction with numerator cap P sub c and denominator cap P sub e end-fraction Pccap P sub c = Pressure of exiting vapor ( kPak cap P a Correlation for Choked Flow
This article provides a masterclass in ejector calculations and explains what makes a "fixed" XLS file a non-negotiable tool for process engineers.