(also known as jet pumps or eductors) are simple yet highly effective devices that use a high-pressure fluid (motive fluid) to entrain and compress a lower-pressure fluid (suction fluid). They are widely used in chemical plants, HVAC systems, vacuum distillation, and wastewater treatment.
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Spreadsheet calculations are approximate. Always:
The area where the low-pressure process gas enters and mixes with the motive steam. ejector design calculation xls
What are your specific (e.g., steam and air)? What is your target operating suction pressure ?
: Specifically used for steam locomotives to maximize draft, these spreadsheets use "trial and error" solvers to optimize the chimney throat diameter against the tuyere (nozzle) area. Gas/Gas Ejectors : Used in oil and gas for energy recovery, these often use CFD-validated correlations to predict discharge pressure within a 2% accuracy range. Key Reference Formulas For a typical steam ejector, the Entrainment Ratio ( under choked conditions is often modeled as:
An ejector uses a high-pressure motive fluid to entrain and compress a low-pressure suction fluid. The process relies entirely on the conversion of pressure energy into kinetic energy, and back into pressure energy, without any moving parts. Key Components (also known as jet pumps or eductors) are
is the diffuser efficiency (typically between 0.75 and 0.85), and is the Mach number of the mixed fluid. 3. Structuring your Excel ( .xls ) Calculation Sheet
For compressible fluids: [ A_t = \fracW_motiveP_1 \cdot \sqrt\frac\gammaR_gas T_1 \cdot \left(\frac2\gamma+1\right)^\frac\gamma+1\gamma-1 ] (Implemented as Excel formula with named constants)
Engineers rely heavily on Excel spreadsheets ( .xls or .xlsx ) to automate these complex formulas. This guide explains the core engineering principles, step-by-step mathematical calculations, and structural design needed to build a robust tool. 1. Fundamentals of Ejector Operation This link or copies made by others cannot be deleted
+-----------------------------------------------------------+ | EJECTOR DESIGN CALCULATION XLS | +-----------------------------------------------------------+ | [Input Data Block] | | --> Motive Fluid Props (P, T, Mw) | | --> Suction Fluid Props (P, T, Mw) | | --> Discharge Target Pressure | +-----------------------------------------------------------+ | [Thermodynamic Engine] | | --> Isentropic Expansion Calculations | | --> Sonic Velocity & Mach Number Checks | +-----------------------------------------------------------+ | [Geometric Output Summary] | | --> Nozzle Throat Diameter (Dt) | | --> Nozzle Exit Diameter (De) | | --> Diffuser Throat Diameter (Dd) | +-----------------------------------------------------------+ Step 1: Input Parameters
): The mass flow rate of entrained vapor divided by the mass flow rate of motive steam. The ratio of discharge pressure ( Pccap P sub c ) to entrained vapor pressure ( Pecap P sub e ). Choked flow is generally defined as Expansion Ratio ( ): The ratio of motive steam pressure ( Ppcap P sub p ) to entrained vapor pressure ( Pecap P sub e Geometry Sizing: Determining the nozzle throat area ( A1cap A sub 1 ), nozzle outlet area ( A2cap A sub 2 ), and diffuser cross-sections. Foundational Research Papers
A spreadsheet tool becomes significantly more complex when dealing with two-phase (liquid-vapor) fluids. Two-phase models often rely on a (rather than a full 1D CFD model) where conservation equations and real fluid properties are used. The model may assume Homogeneous Equilibrium (HEM) —that the liquid and vapor phases are perfectly mixed and in thermal equilibrium. Another strategy for two-phase nozzles is to bypass the complicated two-phase sound speed calculation and instead maximize the mass flow rate at the throat .
Design a single-stage steam ejector to pull 100 kg/h of air from a vessel at 0.2 bar_abs, discharge to 1.0 bar_abs. Motive steam at 5 bar_g, 150°C.