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Generation of Most Eligible Steam for Rankine Cycle. P M V Subbarao Professor Mechanical Engineering Department. Means to AchieveQualities of Working Fluid Preferred by Sir Carnot …. Reheating : A Means to implement High Live Steam Pressure. Supercritical. 593/621 0 C. 593/593 0 C.
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Generation of Most Eligible Steam for Rankine Cycle P M V Subbarao Professor Mechanical Engineering Department Means to AchieveQualities of Working Fluid Preferred by Sir Carnot …..
Reheating : A Means to implement High Live Steam Pressure Supercritical 593/6210C 593/5930C 565/5930C 565/5650C 538/5650C Improvement in Efficiency, % 538/5380C
3sup 3sub T More Bottlenecks to Achieve Supercritical Steam Cycle 2 4sup 4sub 1 s
Quality and Saturated Liquid-Vapor (Wet) Mixture • Now, let’s review the constant pressure heat addition process for water shown in Figure. • The state 3 is a mixture of saturated liquid and saturated vapor. • How do we locate it on the T-v diagram? • To establish the location of state 3 a new parameter called the quality x is defined as
Adiabatic Expansion of Steam • The liquid in the LP turbine expansion flow field is seen to progressively appear, with lowering pressure, in four forms, namely as: • A fine mist (or fog) suspended in the steam; • As a water stream running in rivulets along the casing (mainly OD); • As a water film moving on the surface of the blades (mainly stator; not particularly evident on the rotor blades owing to centrifugal-flinging action); • As larger droplets created when the water flowing along the surface of the blades reaches the trailing edge.
3sup 3sub T More Bottlenecks to Achieve Supercritical Steam Cycle 2 4sup 4sub 1 s
Ill Effects of High Pressure Cycles x Pressure, MPa
Philosophical Recognition of Working Fluid Organic Substances must be selected in accordance to the heat source temperature level (Tcr < Tin source)
Reheating of Steam to Enhance Quality at the Turbine Exit Single Turbine drum
Analysis of Reheat Cycle • Consider reheat cycle as a combination of Rankine cycle and horn cycle. • Cycle 1-2-3-4-5-6-1 = Cycle 1-2-3-4-4’-1 + Cycle 4’-4-5-6-4’. • Therefore, 4’ 6
Clues to Achieve Double Benefit Consider the ratio of Define Increment in efficiency
Selection of Reheat Pressure pmax= 15 MPa Tmax= 550 0C Tsat= 342.20C
Effect of Reheat Pressure on New Tm,in pmax= 15 MPa Tmax= 550 0C Tsat= 342.20C
Effect of Reheat Pressure Dh,% 1.0 0.2 0.4 0.6 0.8 ~0.3 prh/pmax
Reheating : A Means to implement High Live Steam Pressure Supercritical 593/6210C 593/5930C 565/5930C 565/5650C 538/5650C Improvement in Efficiency, % 538/5380C
Reheater Pressure Optimization forDouble Reheat Units 97bar 69bar 110bar
21st century Rankine Cycles Improvement in Efficiency, %
Double Reheat Super Critical Plants Net efficiency on natural gas is expected to reach 49%. Net efficiency on coal is expected to reach 47%.
FUTURE ULTRA SUPERCRITICAL PLANT – UNDER DEVELOPMENT EFFICIENCY 55 %
h Steam Generation : Explore more Causes for Wastage x=s
6 4 6’ 3 2 Synthesis of Rankine Cycle with OFWH 5 T p2=p6 1 7
Analysis of mixing in OFWH y h6 (1-y) h2 Constant pressure mixing process Consider unit mass flow rate of steam thru the turbine h3 Conservation of energy:
Performance of OFWH Cycle ~ 12MPa htotal pbleed, MPa