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									Effect of Reheating and Feed Water Heating
            on Steam Generation




                   P M V Subbarao
                      Professor
          Mechanical Engineering Department




       Good to Turbine and Cycle…..
      What about Steam Generator ???
Dh,%   Effect of Reheat Pressure




       0.2          0.4     0.6   0.8   1.0

             ~0.3
                     prh/pmax
Selection of Optimal Reheat Point
Reheat Supercritical Rankine Cycle

                 3       5




     2s          4



2

                          6
 1
Reheating : A Means to implement High Live Steam
                     Pressure
                               Supercritical
Improvement in Efficiency, %



                                               593/6210C
                                                593/5930C
                                               565/5930C
                                                565/5650C
                                               538/5650C
                                               538/5380C
Single-Reheat Ultrasupercritical Product Line
                 GE Power
Super Critical Cycle ~ 1990
Double Reheat Ultra Super Critical Cycle




8
Reheater Pressure Optimization for
       Double Reheat Units
Improvement in Efficiency, %
 Scope for Double Reheat in Ultra CriticalCycles

                   6100C


                   5380C



           6100C


               5380C


150                    P,bar                       350
Super Critical Cycle of Year 2005
          Double Reheat Super Critical Plants




Net efficiency on natural gas is expected to reach 49%.
Net efficiency on coal is expected to reach 47%.
Super Critical Cycle of year 2010




       > 50 %
Double-Reheat Ultrasupercritical Product Line
                 GE Power
Ultra Supercritical Installations of The World
Reassessment Thru Carnot Model
                         4500C




             3110C

               ~273
               ~2500C
               Non-Isentropic Expansion !!!



                                          4
        A Macro Carnot Cycle !!!!

           3                              5
T



    2
                                    6

    1
                                    7
Ideal Regenerative Cycle

4

     5
                           6

                               7
      3




                       2           1
                                     Regenerative Turbine
                             
                             Q REGEN
                                 3
                                           T

                                                4
                                                   
          SSSF : CM :  min  min

                                                m                               
                                                                                          
Q CV   m in  h  V 2  gz                   in
                                                            out      h  V 2  gz   out
                                                                                            W CV
Regenerative heat transfer. Change in kinetic and potential energies are negligible
                                                                            
              Q REGEN   min  hin   m out  hout  W CV
         Assuming a single fluid entering and leaving…
                                                                           
    W CV   Q REGEN  m hin  hout   m h4  h7   m h3  h2 
Analysis of Regeneration Cycle
                                                                                          4
          
   Q in  mh4  h3                                                       3

                                                            T                           5

   Q out  mh7  h1 
                                                                       2
                                                                                    6
   W turbine  mh4  h7   h3  h2                               1
                                                                                      7
                  
   W pump  mh2  h1                                                          s

                                  Net Power output
        Efficiency of the cycle
                                 Rate of Heat addition
                                       
                           
                                       mh4  h3   h7  h1         h7  h1 
                   h      W net
                                                                    1
                            
                           Q in
                                              
                                             mh4  h3                  h4  h3 
 
S  m s

								
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