IDEAL REGENERATIVE RANKINE CYCLE

• IT RAISES THE TEMPERATURE OF WATER LEAVING THE PUMP (FEED WATER) BEFORE IT IS FED TO BOILER.

• EXTRACTING OR BLEEDING STEAM FROM TURBINE AT A POINT. THIS STEAM WHICH COULD BE USED TO PRODUCE MORE WORK BY EXPANSION IN TURBINE IS USED TO HEAT FEED WATER INSTEAD. THE DEVICE WHERE THE FEED WATER IS HEATED BY REGENRATION IS CALLED REGENERATOT OR FWH.

IDEAL REGENRATIVE RANKINE CYCLE

• IT IMPROVES THE THERMAL EFFICIENCY OF POWER PLANT. • IT PREVENTS DEAREATING- HEATER AT HIGHER PRESSURE

THAN ATMOSPHERIC. IT REMOVES ANY DISSOLVED GASES, PARTICULARLY O2 FROM WATER BEFORE IT IS FED INTO BOILER

• IT IS OPEN OR DIRECT AND CLOSED FWH.• FWH IS A HEAT EXCHANGER WHERE HEAT IS TRANSFERRED

FROM THE STEAM TO THE FEED WATER EITHER BY MIXING THE TWO FLUID STREAMS OR WITHOUT MIXING THEM.

• ADDL BENEFITS----------

OPEN WATER & CLOSE WATER HEATER

BENEFITS OF REGENERATION

• STEAM FLOW TO CONDENSOR ARE REDUCED HENCE;

• SMALLER CONDENSOR AND BOILER• DIFFICULTY OF PASSING LARGE VOLUME OF

STEAM THROUGH THE LAST STAGES IN TURBINE IS LESSENED.

• INCREASED BLADE HEIGHTS TO ACCOMMODATE THE INITIAL STEAM CONSUMPTIONS

• TURBINE LESS EXPOSED TO EROSION.

COMPARISON OF REGENRATIVE WITH REHEAT

• REHEAT LARGE AND LONG PIPES ARE NEEDED WHICH MEANS EXTRA COST.

• LARGE PRESSURE DROPS OCCURS IN THE PIPING.• PROVISION FOR EXPANSION AND CONTRACTION OF

PIPES JOINTS IS TO BE MADE..• REHEAT IS COMPLICATED SYSTEM AS…• DETERMINATION OF SUITABLE REHEAT PRESSURE LEVEL

IS PROBLEM AND ENTAILS NO OF CONSIDERATIONS• LOW HEAT INPUT HENCE LOWER EFFICIENCY IN REHEAT

v

NUMERICAL/ASSIGNMENT NO 3

• CONSIDER A REGENRATIVE VAPOUR POWER CYCLE WITH ONE FEED WATER HEATER. STEAM ENTERS THE TURBINE AT 8 MPa, 480° C AND EXPANDS TO .7 MPa, WHERE SOME OF THE STEAM IS EXTRACTED AND DIVERTED TO THE OPEN FEED WATER HEATER OPERATING AT .7 MPa. THE REMAINING STEAM EXPANDS THROUGH THE SECOND STAGE TURBINE TO THE CONDENSOR PRESSURE OF .008 MPa. SATURATED LIQUID EXISTS THE OPEN FEED WATER HEATER AT .7 MPa.ISENTROPIC EFFICIENCY OF EACH TURBINE STAGE IS 85 % AND EACH PP OPERATES ISENTROPICALLY. IF THE NET POWER OUTPUT OF THE CYCLE IS 100 MW, DETERMINE. A. thermal efficiency B. mass flow rate of steam entering the first turbine stage in kg/h.

NUMERICAL/ ASSIGNMENT 4

• STEAM IS WORKING FLUID IN AN IDEAL RANKINE CYCLE WITH SUPERHEAT AND REHEAT.STEAM ENTERS THE FIRST STAGE TURBINE AT 8 Mpa 480 CELSIUS AND EXPAND TO .7 Mpa. IT IS THEN REHEATED TO 440 CELSIUS BEFORE ENTERING THE SECOND STAGE TURBINE, WHERE IT EXPANDS TO THE CONDENSOR PRESSURE OF .008 Kpa. THE NET POWER OUTPUT IS 100 MW. DETERMINE

• THERMAL EFFICIENCY 2.MASS FLOW RATE OF THE STEAM IN KG/H 3. RATE OF HEAT TRANSFER FROM THE CONDENSING CYCLE AS IT PASSES THROUGH THE CONDENSOR IN MW. DISCUSS THE EFFECT OF REHEAT ON THE VAPOUR POWER CYCLE?