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ejector design calculation xls
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Calculation Xls | Ejector Design

Limitations:

Recommendations:

Motive nozzle exit Mach (choked):
[ M_e = \sqrt\frac2\gamma-1\left[ \left(\fracP_mP_exit\right)^\frac\gamma-1\gamma -1 \right] ]
Excel: =SQRT((2/(gamma-1))*((P_m/P_exit)^((gamma-1)/gamma)-1))

Area ratio from Mach:
[ \fracAA^* = \frac1M\left(\frac2\gamma+1\left(1+\frac\gamma-12M^2\right)\right)^\frac\gamma+12(\gamma-1) ]
Excel: = (1/M)*((2/(gamma+1))*(1+((gamma-1)/2)*M^2))^((gamma+1)/(2*(gamma-1)))

Entrainment ratio from momentum (constant-area mixing, no shock):
Implemented via iterative Goal Seek or explicit solve. ejector design calculation xls

| Row | Column A (Label) | Column B (Value) | Column C (Units) | | :--- | :--- | :--- | :--- | | 1 | SUCTION CONDITIONS | | | | 2 | Suction Pressure ($P_s$) | [Input Value] | bar(a) | | 3 | Suction Temperature ($T_s$) | [Input Value] | °C | | 4 | Suction Mass Flow ($M_s$) | [Input Value] | kg/hr | | 5 | Molecular Weight (MW) | [Input Value] | kg/kmol | | 6 | MOTIVE STEAM CONDITIONS | | | | 7 | Motive Pressure ($P_m$) | [Input Value] | bar(a) | | 8 | Motive Temperature ($T_m$) | [Input Value] | °C | | 9 | DISCHARGE CONDITIONS | | | | 10 | Discharge Pressure ($P_d$) | [Input Value] | bar(a) |

Once you have the mass flows converged, calculate the geometry.

1. Nozzle Throat Diameter ($d_t$): $$d_t = \sqrt\frac4 \times M_m\pi \times \rho_throat \times V_throat$$

2. Diffuser Throat Diameter ($D_t$): This is often sized based on a specific velocity (Mach 1) at the mix pressure. A common heuristic formula used in XLS sheets for steam: $$D_t \approx \sqrtd_t^2 \times \left( \fracP_mP_s \right)^0.5 + \textSuction Area Factor$$ (For exact calculation, you must determine the specific volume of the mixture at the diffuser throat). Limitations:

Ejectors (also known as jet pumps, eductors, or siphon pumps) are simple yet highly efficient devices that use the Venturi effect to transport fluids, gases, or slurries. Unlike mechanical pumps, ejectors have no moving parts, making them ideal for harsh environments, high-temperature applications, and explosive atmospheres. However, designing an ejector is a delicate balance of fluid dynamics, thermodynamics, and empirical correction factors.

For decades, engineers have relied on specialized software or complex hand calculations. But with the power of Microsoft Excel, you can create a transparent, flexible, and accurate ejector design calculation spreadsheet (.xls). This article provides a comprehensive guide to the theory, step-by-step calculations, and the structure of a professional-grade .xls tool.

[ CR = \fracP_3P_2 \quad \text(absolute pressures) ]

Assume isentropic expansion. For an ideal gas: $$M_m = \sqrt \frac2k-1 \left[ \left( \fracP_mP_s \right)^\frack-1k - 1 \right] $$ Recommendations:

In Excel formula (for k=1.4, air): =SQRT((2/0.4)*((P_m/P_s)^(0.4/1.4)-1))

But wait – if $P_m/P_s$ exceeds the critical pressure ratio (approx 1.89 for air), Mach is >1. Most ejectors operate supersonically (M=1.5 to 4.0). Your XLS should cap Mach using the critical ratio.

This Excel sheet is built upon the One-Dimensional Flow Theory and the Conservation of Energy and Mass.