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8 comments
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Join Date: Jan 2010
Posts: 9

Using a Vacuum in a Condenser in a Thermal Power Plant

01/25/2010 11:46 AM

sir, i want to know how the pressure inside the condensor will effect the other parameter if it exceeds from rated value, tell me in detail how the condensor pressure effect the turbine efficiency

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#1

Re: use of vaccume in condensor in thermal power plant

01/25/2010 11:57 AM

Its use may be discovered in textbooks on Thermodynamics. However, the simple principle is that, by condensing the steam coming off a turbine, one pulls a vacuum on that turbine and therefore gets more work out of the steam for the same charge of fuel compared to not pulling that vacuum. The lower the condenser temperature, the higher the efficiency. The increase is marginal, though worth it for a medium-to-large installation.

Clearly the device itself needs to be rated for full vacuum.

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#2

Re: Using a Vacuum in a Condenser in a Thermal Power Plant

01/25/2010 7:43 PM

'exceeds from rated value' is vague. Are you asking what happens to the condenser if it is exposed to excessive pressure, or are you asking what happens if the plant runs with less than ideal vacuum ?

By the way, if this is homework, you are setting yourself up for failure. You need to understand this and you won't be able to ask someone it really counts.

First case: If the condenser experiences sufficient pressure, condenser tube integrity may be diminished. If leaks occur and not repaired, then when vaccuum is eventually drawn, air and other impurities will enter. Steam plant chemistry will be thrown out of whack. Your chemist will be pissed. Your boilers will be at risk. Efficiency will be in the crapper because air entering the system won't allow a decent vacuum, but especially because you have to shut down to repair the condenser.

Second case: Lower than optimal vacuum.... The short answer is that the plant will generate less for the same heat input. Higher pressure in the condenser means higher enthalpy leaving the turbine...so delta H is smaller.. less available to do what you need. If vaccuum is poor, there is a cause... fouling of condenser tubes, air leak, high cooling water temp, low cooling water flow rate, manatee poop or jellyfish...no I covered that...

Benbenben

p.s. Often, the quickest way to destroy a lazy man is to give him exactly what he thinks he wants.

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Power-User

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#3

Re: Using a Vacuum in a Condenser in a Thermal Power Plant

01/26/2010 5:33 PM

I don't mean to insult your intelligence with this but it is best visualized as a series of water falls down a mountain, if you put a water wheel at each water fall you will capture the energy at each level. The vacuum is as if you were to dig an additional water fall then you could add another water wheel.

If you are questioning why your plant was designed to have less than what would appear to be a perfect vacuum you may want to look at your station elevation.

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Participant

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#4

Re: Using a Vacuum in a Condenser in a Thermal Power Plant

01/28/2010 8:49 AM

Condenser pressure must be lower than atmospheric pressure so the suction of steam from turbine exit will not create back pressure on turbine blade which directle leads to turbine efficiency. Temperature and pressure both at turbine exaust are low then inlet due to expansion of steam. condensor cools the steam to water and resubmit it to bolier.

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Member

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#5
In reply to #4

Re: Using a Vacuum in a Condenser in a Thermal Power Plant

01/28/2010 11:30 AM

sir,ok but i want to know what will happen if we maintain less than the required pressure my mean if we maintain more vaccum than required

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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#6
In reply to #5

Re: Using a Vacuum in a Condenser in a Thermal Power Plant

01/29/2010 9:12 AM

The vacuum will be the liquid-vapour transition pressure ("boiling"/"condensing") for water at that temperature. The cooler the condenser, the stronger the suck. See steam tables: Mayhew & Rogers "Thermodynamic Properties of Fluids", Perry "The Chemical Engineer's Handbook" any edition, "Kempe's Engineers' Yearbook" any edition, etc., etc., yada yada......

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Anonymous Poster
#7
In reply to #5

Re: Using a Vacuum in a Condenser in a Thermal Power Plant

01/29/2010 9:14 AM

Check here only for study.

If you are playing with turbine, leave it to OEM, the components are designed for a parameter and if you experiment, these may fail.

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Anonymous Poster
#8
In reply to #7

Re: Using a Vacuum in a Condenser in a Thermal Power Plant

02/25/2010 3:20 PM

we use Vacuum in a Condenser in a Thermal Power because we want maximum amount of work to be done by steam on the same heat

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