What are Condensing Turbines and Back Pressure Turbines
Condensing turbine get their name from their ability condenses steam in one of their outlet. Condensing turbine has two outlets from which one is used to utilize the medium pressure steam for heating process and other outlet do condensation process by utilize the low pressure steam. At the outlet (where medium pressure steam is utilize to get heating) on control value is present which is used to control the flow of steam over that outlet. By controlling the steam flow over that outlet the production of condensation process can be increased or decreased. The second outlet moves the steam to the condensation chamber where water flow over this steam. When water flow over high temperature steam, it absorb heat from the steam and get condense and then that condense water is moved toward boiler of the condensing turbine.
The condensing turbine process starts with the entry of the high pressure and high temperature steam into the turbine section where it is utilize by the blades of the turbine to produce power. After the production of power the portion of steam which have moderate pressure is move out through first outlet to be utilized for heating and the portion of the steam whose pressure is to low to be used for any type of power production is move out through second outlet towards the condenser. In condenser water remove heat from steam and condense water is again move towards the boiler of the turbine.
Back Pressure Turbine
The back pressure steam turbine is one in which steam at high pressure and high temperature enters the turbine and that steam is used to rotate the turbine blades for power production. Back pressure steam turbine is also called the condensing steam turbine and reason for that is this turbine does not have condenser at its outlet and it has only one outlet.
Working of back pressure steam turbine start with the entry of the high pressure steam into turbine power generation section where blades are present. Blades absorb power from steam and use it to product rotation in shaft of turbine. After providing power for shaft rotation, steam at low pressure and temperature exit the turbine from the outlet into the atmosphere and this is also the main difference between condensing and back pressure turbines. In back pressure turbine the outlet pressure of steam is so low that it cannot be used for any work. This outlet pressure depends on the load on turbine.