Ejector Design Calculation Xls Fixed • Verified Source

Higher temperatures increase the volume, requiring a larger ejector.

Sizes the constant area section to ensure effective momentum transfer between the motive and suction fluids. Diffuser Geometry:

To build a robust calculation sheet, you must define the following input variables: A. Motive Fluid Properties Usually high-pressure steam or air. Temperature ( Tmcap T sub m ): Needed to determine specific volume. Flow Rate ( Wmcap W sub m ): The mass flow available to do the work. B. Suction Fluid Properties Suction Pressure ( Pscap P sub s ): The vacuum level you aim to maintain. Entrainment Ratio ( ): The ratio of suction gas to motive gas ( ). This is the most critical output of your calculation. C. Discharge Conditions Discharge Pressure ( Pdcap P sub d ): The pressure the ejector must overcome (back-pressure). 3. The Step-by-Step Calculation Process

Calculates the area required for the motive fluid to expand and create a vacuum. ejector design calculation xls fixed

For a fixed nozzle, the motive steam flow is calculated based on the nozzle throat diameter and the motive fluid's pressure and temperature. A common formula for motive flow involves:

, the flow is choked, and you must use the sonic flow equation for Atcap A sub t detailed in Section 2. 4. Hardcoded Efficiency Factors

: $$A_t = \frac\dotm_mP_m \times \frac1C_d \times \sqrt \fracR T_mk \left( \frack+12 \right)^\frack+1k-1 $$ Excel Formula (assuming $R=8314/M_m$ and $C_d = 0.95$): =(B11/B2) * (1/0.95) * SQRT( ( (8314/B7)*B5 / B9 ) * ((B9+1)/2)^((B9+1)/(B9-1)) ) Higher temperatures increase the volume, requiring a larger

) will lead to 'choking' or 'backflow' in fixed-nozzle designs." Efficiency (

This article breaks down the essential steps for ejector design and how to effectively use Excel-based tools to streamline the process. Why Use an Excel-Based Ejector Design Tool?

To generate an accurate design, the following parameters must be entered into the spreadsheet: Motive Fluid Data: Pressure ( cap P sub m ), Temperature ( cap T sub m ), and Flow Rate ( cap W sub m Suction Fluid Data: Pressure ( cap P sub s ), Temperature ( cap T sub s ), Molecular Weight ( cap M cap W ), and Flow Rate ( cap W sub s Discharge Data: Required Discharge Pressure ( cap P sub d System Constraints: Compression Ratio ( ) and Expansion Ratio ( 3. Core Calculation Methodology Motive Fluid Properties Usually high-pressure steam or air

An ejector works on the Bernoulli principle, where a high-pressure passes through a converging-diverging nozzle, creating a high-velocity, low-pressure jet. This jet entrains a suction fluid , mixes with it, and then decelerates in a diffuser to a higher discharge pressure.

: $$P_m^* = P_m \times r_c$$ Excel Formula: =B2 * [Critical_Ratio_Cell]

) does not exceed the "critical discharge pressure." If it does, the shockwave will move back into the throat, and the ejector will stop suctioning (breaking the vacuum). 4. Structuring Your XLS for Accuracy

Em=MWactualMWair⋅TairTactualcap E m equals the square root of the fraction with numerator cap M cap W sub a c t u a l end-sub and denominator cap M cap W sub a i r end-sub end-fraction end-root center dot the square root of the fraction with numerator cap T sub a i r end-sub and denominator cap T sub a c t u a l end-sub end-fraction end-root 4. Step-by-Step Architecture for your XLS Spreadsheet