The document summarizes the operating principles and characteristics of a steam ejector. It describes how a steam ejector can function as either a feedwater heater or feedwater pump. As a heater, steam condensation transfers energy to water being heated. As a pump, the velocity of steam through a convergent nozzle lifts water from a suction tank to a delivery tank. Key equations are provided relating the efficiency of the ejector to process parameters like steam and water flow rates, temperatures and pressures. Test data from an ejector rig is summarized in a table showing parameter measurements at different operating pressures. Engineering drawings and definitions of key concepts like vacuum are also requested.

1. Steamejectorcharacteristics
1- Apparatusused
1- Electrical boiler.
2- Ejectorrig.
2-Theory
The ejectorunitcan performtwofunctions.Itcan act as feedwaterheateror a feedwaterpump.When
consideredasa feedheater,the energygivenupthe steamupon condensingisabsorbedbywater.The
efficiencyof thisheattransferisgivenby:
𝑒𝑓𝑓𝑐𝑖𝑒𝑛𝑐𝑦 =
𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑚𝑝𝑎𝑟𝑡𝑒𝑑 𝑡𝑜𝑤𝑎𝑡𝑒𝑟
𝑒𝑛𝑒𝑟𝑔𝑦 𝑔𝑖𝑣𝑒𝑛 𝑏𝑦 𝑠𝑡𝑒𝑎𝑚
𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =
𝑚𝑤𝐶𝑝𝑤(𝑡2 − 𝑡1)
𝑚𝑠[𝑥. ℎ𝑓𝑔 + 𝐶𝑝𝑤(𝑡𝑠𝑎𝑡. − 𝑡2)]
Where
mw = Mass of water persecond.
Ms = Mass of steamper second
Cp = Specificheatcapacityof water,kJ/kg.K
hfg = Latent heatof evaporationatsteampressure,kJ/kg.
x = Steamquality.
Ts = Saturationtemperature of steam,K.
T1 = Temperature of watersuppliedtoejector,K.
T2 = Temperature of waterdeliveredbyejector,K.
And
𝑚𝑠 =
𝐴𝑡 𝑃𝑜
√𝑇0
√𝑘
𝑅
(
2
𝑘+1
)
𝑘+1
𝑘−1
Where:
K = steamindex =1.133 forsteaminitiallywet.
Po = stagnationsteampressure,pa.
To = stagnationtemperature,k.
R = specificsteamconstant= 0.461 kJ/kg.Kforsteam.

2. At = throat area, m2
Whenacting as a feedwaterpumpthe flow of steamthroughthe convergentnozzle causesachange
frompressure energytovelocityenergy.The increasedvelocityof steamisacomposedbya reduction
inpressure sufficienttocause the waterinthe lowertankto be liftedthroughthe waterinletpipe.
Condensationof the steamflowingthroughthe nozzlebyflow of waterfurtherreducesthe pressureat
the top of the inletpipe andincreasesthe flow of water.The energygivenupbythe steamasit passes
throughthe ejectorisusedto liftthe waterfromsuctiontank tothe deliverytank.
Energygivenupby the steam= Enthalpyof evaporation +enthalpyof liquid
= 𝑚𝑠[𝑥.ℎ𝑓𝑔 + 𝐶𝑝𝑤(𝑡𝑠𝑎𝑡. − 𝑡2)]
Work done inliftingwater=force * distance
= gravitational force onmassof waterlifted*meanheadlifted
Where, g = gravitational acceleration,9.8m/s2
.
H = meanheadlifted,m
= pressure head + meansuctionhead
1 bar = 10.3 m of water.
pump =
work done
energy supplied
pump =
𝑚𝑤.𝑔.𝐻
𝑚𝑠[𝑥. ℎ𝑓𝑔 + 𝐶𝑝𝑤(𝑡𝑠 − 𝑡2)]
3-Measurement:
The followingparametersare measuredduringthe ejectorrigtestas summarizedinthe table
below:
Parameter
pressure
1 bar 2 bar 2.5 bar 3 bar 3.5 bar 4 bar
Duration(sec)
Initial suctiontanklevel,cm
Final suctiontanklevel,cm
Initial deliverytanklevel,cm
Final deliverytanklevel,cm
Suctionwatertemperature, o
C
Deliverywatertemperature, o
C

3. Notes:
Tank capacity 958 ml/cm
Suctionlevel 75 cm
4-Requirements:
1- Draw the relationbetweenthe sreampressrure andthe efficiencyof the ejectorasa pumpand
heatexchangeranddiscussthe results.
2- What are the advantagesof steamejectorasusedin powerplantstations?Draw the
engineeringdrawingof the ejector.
3- Define vacuum?Howcan itbe obtained?Explaininbrief.
Ejectorrig schematicdiagram:
Suction tank
Deliverytank
Deliverypressure
temperature
pressure
Flow meter
Steam ejector
Deliverytemperature