The search for is not about finding a lazy shortcut. It is about finding a transparent, iterative, engineering-driven tool that respects the laws of gas dynamics while giving you immediate feedback on geometry changes.
An ejector consists of three primary components: a motive nozzle, a mixing chamber, and a diffuser. The system relies heavily on and the Ideal Gas Law to function.
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 ):
A robust spreadsheet typically follows these sequential calculations: Key Formula/Logic Compression Ratio ( CRcap C cap R ) Assess performance feasibility 2 Expansion Ratio ( ERcap E cap R ) Determine motive energy 3 Entrainment Ratio ( ) Calculate suction capacity (Use semi-empirical constants A–H) 4 Nozzle Sizing Find throat ( A1cap A sub 1 ) & outlet area ( A2cap A sub 2 and isentropic expansion 5 Mixing & Diffuser Find mixing diameter ( A3cap A sub 3 Function of combined mass flow and Pccap P sub c 3. Critical Formulas for Excel Use these semi-empirical equations (valid for ) in your cells: Entrainment Ratio ( ): Constants (approximate): Nozzle Throat Area ( A1cap A sub 1 ): 4. Implementation Resources ejector design calculation xls
Combines the high-velocity motive stream with the low-pressure suction stream.
The zone where momentum transfer occurs between the motive and suction fluids, often resulting in a normal shock wave that increases static pressure.
[ CR = \fracP_3P_2 \quad \text(absolute pressures) ] The search for is not about finding a lazy shortcut
dt=4⋅Atπd sub t equals the square root of the fraction with numerator 4 center dot cap A sub t and denominator pi end-fraction end-root 5. Limitations of Empirical XLS Models
A proper XLS tool must first define the process conditions for both the Motive Fluid (driving force) and the Suction Fluid (entrained load). Motive Pressure ( cap P sub p ) & Temperature ( cap T sub p Typically high-pressure steam. Suction Pressure ( cap P sub e ) & Temperature ( cap T sub s The required vacuum level. Discharge Pressure ( cap P sub c The pressure at the outlet, often directed to a condenser. Entrainment Ratio ( Ratio of suction mass flow ( ) to motive mass flow ( ScienceDirect.com 2. Core Calculation Steps
When downloading from independent sites, always validate the results against a known case or a commercial tool before using them for final design. The system relies heavily on and the Ideal
If steam condenses during expansion in the nozzle, ideal gas equations fail.
To begin an XLS calculation, you must define the following operating conditions: Pressure ( Pmcap P sub m ), Temperature ( Tmcap T sub m ), and Molecular Weight ( MWmcap M cap W sub m Suction Fluid: Pressure ( Pscap P sub s ), Temperature ( Tscap T sub s ), and Molecular Weight ( MWscap M cap W sub s Discharge: Required Discharge Pressure ( Pdcap P sub d 2. The Calculation Process
Ejector Design Calculation XLS: A Comprehensive Guide to Spreadsheet-Based Optimization
(using techniques from ScienceDirect ). 4. Why Use an XLS-Based Approach?