) is calculated using the continuity equation based on the mixture density ( ρmixrho sub m i x end-sub ) and critical velocity at diffuser conditions:
With the theory established, let's build the spreadsheet. The following section outlines a practical, step-by-step approach to creating an Excel-based design tool.
Mixing in the mixing chamber (momentum and energy balance)
The diffuser converts the high-velocity mixed fluid's kinetic energy back into pressure. Its design is key to achieving the desired discharge pressure. ejector design calculation xls
, the following framework details the core calculations required for a professional-grade XLS design tool. 1. Key Design Parameters (Inputs)
Motive Fluid (High Pressure) \ v |‾‾‾\ ==================| \_____ _____________________ Suction Fluid --> | _____| / \ ===> Discharge (Low Pressure) | / \_____________________/ (Intermediate) |___/ Nozzle Throat Diffuser (Mixing) Key Components
Ensure mixing velocities do not exceed sonic speeds inappropriately (unless designed to). Optimize Motive Flow: Minimize Wmcap W sub m for the required Wscap W sub s to reduce energy costs. Benefits of the XLS Approach Speed: Instant recalculation when changing inputs. ) is calculated using the continuity equation based
Once corrected, you calculate the required Motive Steam Flow ( ) using the target Entrainment Ratio ( ) for your specific pressure lift ratio ( Step 3.2: Motive Nozzle Sizing (Throat Area)
A diverging section that slows down the mixed fluid, converting kinetic energy back into static pressure higher than the suction pressure. 2. Essential Design Inputs for your XLS Tool
A robust Excel template typically incorporates the following fundamental equations: 1. Entrainment Ratio ( Its design is key to achieving the desired
A sample chart generated from the spreadsheet shows that increasing ( P_m ) from 5 to 10 bar raises ω by ~40% for constant back pressure.
Utilize Excel's Data Table tool or VBA arrays to plot the relationship between suction pressure and entrainment ratio. This creates the characteristic curve of the ejector. 4. Excel Implementation Matrix
w=mempw equals the fraction with numerator m sub e and denominator m sub p end-fraction