28-06-2012, 06:06 PM
Condensers
Condensers.ppt (Size: 11.01 MB / Downloads: 783)
Flow of Presentation
Rankine cycle
Necessity of Condenser
Condensation and its modes
Condenser description and its classification
Constructional features
Condenser sizing
Performance testing
Necessity of Condenser
As per Rankine Cycle the maximum thermal efficiency of a power system is given by
ή = 1- t2 / t1 (t1 and t2 are supply and exhaust steam temp).
To increase cycle efficiency,
Increase supply steam temp.(t1) to maximum, however it is limited by material consideration.
Decrease Turbine exhaust steam temp ( t2 ) to minimum
The temp t2 can be reduced if the exhaust of the turbine takes place below the atmospheric pressure in closed vessel known as CONDENSER, where pressure is maintained below the atmospheric pressure by condensing the steam with circulation of cold water.
What is condensation?
Change in the phase of matter from the gaseous phase (of an element/ chemical species) into liquid droplets or solid grains of the same element/ chemical species.
It occurs when saturated/unsaturated vapor comes in contact with a surface at lower temperature.
Drop wise condensation:-
Vapor condenses into small liquid droplets of various
sizes which fall down the surface in random fashion.
Occurs if surface is coated with a substance that
inhibits wetting. Drops form in cracks, pits and
cavities on surface and may grow and coalesce
together though continued condensation.
Very high heat transfer coefficient compared to
Film wise condensation. But the values can
degrade to values in the range of film wise values.
This mode is promoted by:- Surface coating (e.g.. with PTFE)
Surface Condenser Components:
Steam condensing shell
Water box and CW Connections for Circulating water
Tubes, Tube sheet and support plates
Condensate hot well and CEP connections
Connection to vacuum creating devices (i.e. SE/VP)
Connections for make up DM water supply
Auxiliary connections
Constructional features:
Condenser divided into two parts (by placing two water boxes) to take half condenser into service if required.
Manholes provided for routine maintenance and visual inspection.
Venting and draining arrangement provided for water boxes
Tubes arranged so that there is equal distribution of steam on tube nest with minimum resistance to steam flow
Non condensable gases are continuously sucked with the help of steam ejector/vacuum pump
LP Heaters 1,2 are located inside the upper part of condenser neck.
Condenser is supported on springs in order to allow expansion along height
Baffle plates are provided to guide the steam on the tube nest.