integrated brayton and rankine cycle

integration of rankine and bra\yton cycle

1. A Presentation on integration of Rankine and Brayton Cycle Presented by: Manish Kumar Jaiswal Upendra Yadav Vikas Upadhyay Pushpendra Mishra Vamshi Kanuganti Amit srivastave Instructor :Dr Laltu Chandra

2. Outline Block & T-s diagram of combined cycle Calculations for inputs of heat exchanger Working Principle for heat exchanger Design Principles for heat exchanger Calculations for dimensions

3. Exhaust gases from Brayton at 650ċ is used to superheat the saturated steam coming out of boiler at 311.1ċ because irreversiblity in superheater is lesser when compared to other parts. From energy balance Heat lost by exhaust gasses=heat gain by steam Exhaust temprature of gases comes to be 613k. So this exhaust can be used in regeneration of Brayton Cycle

4. T1 C SG &E T2 CD CP HI =HEAT INPUT T1= BRAYTON TURBINE SH=SUPER HEATER RG=REGENERATOR C= COMPERSOR IC= INTER COOLER T2=RANKINE TURBINE CD=CONDENSOR CP=CONDESATE PUMP SG&E=STEAM GENERATOR AND ECONOMISER HI RG SH IC

5. T 3 4 T2=47.89 ᴼC 1 6 5 f e g h a b c i d a-b=isentropic compression a-c=non isentropic compression c- i =heat recovered in regeneration i -d=heat added in heat exchanger d-e= isentropic expansion d-f= non isentropic expansion f-g= heat transfer to saturated steam in super heater g-h= heat transfer from hot fluid in regenerator h-a=heat rejected to inter cooler 1-2= isentropic pump 2-3= heat added in economizer 3-4= heat added in steam generator 4-5= heat added in super heat exchanger 5-6= turbine expansion 6-1= isobaric heat rejection

6. Temperature ‘C Enthalpy(KJ/Kg) 1 45.8 191.8 2 45.8 201.89 3 311.11 1407.6 4 311.11 2724.7 5 400 3096.5 6 45.8 1966.38 Rankine cycle Design Parameters

7. Parameter Value Compressor Type Radial Centrifugal Compressor Pressure Ratio 4.8:1 (Optimum) Compressor Inlet Temp. 339K Compressor Outlet Temp. 578.6K Isentropic efficiency of Compressor 80% (assumed) Fuel type Natural Gas Calorific Value 12,500Kcal/kg Turbine Type Radial Turbine (ABB MT100) Turbine Inlet Temp. 1223K Turbine Outlet Temp. 923K Isentropic efficiency Of Turbine 85% (Assumed) Brayton Cycle Design Parameter

8. CALCULATIONS Heat required to produce 1000kw by Rankine cycle =2573kw Heat supplied in superheater section=330.64 Heat supplied in steam generator section=1170.9019 Heat supplied in economiser section=1205.8

9. Working principle of superheated steam heat exchanger

10. Design procedure for heat exchanger Steps to be followed

11. STEP 6 Select tube material, decide the tube diameter (ID , OD ), its wall thickness (in terms of BWG or SWG) and tube length . Calculate the number of tubes required to provide the heat transfer area.

12. IF calculated error is less than 30 % Y E S NO Yes then go to next step 11 Then go back to step 5 and re calculate the area using calculated U

13. Design Calculations: Mean Temprature of hot fluid=556.80ċ Mean Temprature of cold fluid=355.55ċ Thermophysical Property at mean temprature Property Hot (Air T=550Ċ ) Cold fluid (Steam p=100b;t=355Ċ) Viscosity 2.849*e-5 [pa s] 2.23 887791*e-5[Pa s] Thermal conductivity 4.357 *e-5[KW/m K] 0.067790711[W/m K] Constant Pressure Specific heat 1.0398[kJ/kg K] 3.862395 [kJ/kg K] Density 0.6418[kg / m 3] 43.6832023 [kg/ m 3]

14. Step 2: Heat duty of heat exchanger m˚(h5-h4)=330.708kw Step 3:we assume overall heat transfer cofficient to be 65 w/m ²c step4:LMTD=155.88K ∆ T 2 =89K ∆T1=250K

15. Step 5:A=Q/(U*LMTD*CF) CF=Correction factor=0.95(taken from hmt data book) A=34.268m ² Step 6:Brass is selected essentially as tube material(K=109 w/ mk ) 1 shell and two tube pass is essentially assumed . Considering 14 BWG OD=30 cm Length=37.5 cm Id=21.83 cm No of tubes=total area /surface area of pipe =34.268/( π *d*l)=49 Step7: Calculated U comes to be 5w/ m ²k % error =100*(65-5)/65=92.35% Now we will go to step 3 and will proceed further