Answer / syed shahid

The steam pressure in the last stage of the steam turbine
is very low after performing the work. To make the steam
flow to the condenser to convert into condensate
(liquid/water)it is necessary that the pressure be much
lower in the condenser to make the steam flow to the
condenser.Therefore, vacuum is maintained in the condenser
using either vacuum pump or steam ejector.

Answer / sethu

How vacuum is created?

Basic vacuum created in the LPT exhaust side is because of condensing process. Phase change is occurring at the exhaust side i.e. conversion of steam into water. Specific volume of water is much lower than the steam.Hence when the condensing process happens, volume of steam reduces and basic vacuum is created.

Apart from this, vacuum pumps are provided to remove non condensable gases/air ingress which reduces heat transfer effectiveness.

Why vacuum is created?
To improve LPT cylinder efficiency & thus the load/work done shall be improved.

Effect of over vacuum?
It causes sub-cooling effect where hot well temperature reduces more than design which required to be added in boiler leads to heat loss. Also flow accelerated erosion in LPT last stages.

Effect of under vacuum?
LPT efficiency reduction which causes lesser work done & leads to reduced load output.

Answer / jahanzaib

If we answer it in simole way then we just answer that to
avoid back pressure on steam turbine we maintain vacuum in
condensor......(This is the answer Why we create vacuum in
condensing turbine)
Second question some one ask what happend if vacuum loss
occure in condensor then we explain that
.)work done by steam turbine will reduced that will
eltimately reduce the effency of steam turbine.
.)LP turbine side temperature will start risisng casuning
damage to LP side turbine blades.

Answer / rajkumar

vacumm is only maintaining for rising the turbine workdone,
how means it will reduce turbine outlet temperature due to
long time expansion wih out condensation of steam on last
turbine stages corresponding to the vaccum pressure,
that means max heat will be recoverd on turbine,
and also already temp less of turbine exhaust so condensor
cooling water flow also needed less

Answer / jk gangwar

Its main purposes remove for non condense gas's in steam. If here is not vaccum then may be steam condensate drops collected on turbine blades and can damage turbine blades and turbine casing. Overall turbine work efficiency will increase if vaccum apply in surface condenser. In Common case we use Steam injector's in series with primary and secondary injector's and condenser.

Answer / venkatesh

Vacuum is created in condensor because in LPT turbine steam having less pressure after expansion so we need that steam to convert into water.So at 1 atm and 100 deg water will convert into steam.At lower temp we need to convert steam in to water so we used vacuum pump to create negative pressure.if we achived Ideally -1 vacuum then their is no loss of water but practically it is not possible max we can reach -0.9 vacuum.
concl:Vaccum is needed to convert low temp stm into water.

Answer / anirban

Vacuum is created in condenser due to regular flow of steam in turbine nd create it's condensate.as much lower the pressure is it helps to built more condensate by using ejectors or hogger

Answer / c.reddi sankara

Sudden expansion of steam in the condenser space which is higher enough to drop the pressure below then atmospheric pressure is the cause to create negative pressure or vacuum.(And air pumps are also used to create vacuum).
As we know any gas will expand and cooled immediately in vacuum due to negative pressure.
Hence when the pressured steam expanded suddenly in in vacuum and cooled then the cycle efficiency will increases.

Answer / ragi sunil chowdary

more
kinetic
energy get
from more
pressure
difference
so if we
create
vaccume in
condenser
max pres
dif wil b
created. By
dat
efficiency
wil
improove.
If dere is
no pressure
difference
between
turbine
inlet and
outlet
(condenser)
how steam
flows?

Answer / hmt

to let no ionization occur there is vaccum inside the
condenser.

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