First Law Analysis of Steam Power Plants

1. First Law Analysis of Steam Power Plants P M V Subbarao Professor Mechanical Engineering Department Clues to Generate Highly Peroforming Steam …..

2. Laws of Nature for A Control Mass Conservation of Mass : Conservation of Momentum : First law of thermodynamics :

3. Rate Equations for Laws of Nature for A Control Mass Conservation of Mass : Conservation of Momentum : First law of thermodynamics :

4. The Thermodynamic Control Volume • In real engineering devices, we are usually interested in a region of space, i.e, control volume and not particular control mass. • The laws of nature are connected to Control Mass. • Therefore, we need to transform Laws of Conservation for a control mass to a control volume. • This is accomplished through the use of Reynolds Transport Theorem. • Specially derived in thermodynamics for CV .

5. III At time t0+dt II II I At time t0 Reynolds' Transport Theorem III has left CV at time t0+dt I is trying to enter CV at time t0 The control volume may move as time passes.

6. Laws of Nature for A Control Volume • Conservation of mass: • Conservation of momentum: • Conservation of energy:

7. First Law for CV: Steady State Steady Flow Properties of CV are Invariant: • Conservation of mass: NO accumulation or depletion of mass of a CV. • Conservation of energy: No addition or removal of energy for a CV.

8. Let : Rate of Work and Heat Transfers : SSSF Both rate of heat transfer and rate of work transfer are invariant. The work done per unit mass and heat transfer per unit mass are invariant. The specific work transfer at various parts of a CV can be different. The specific heat transfer at various parts of a CV can be different.

9. Layout of Equipment :The Simple Rankine Cycle

10. Pump : ADIABATIC Process 1 2 SSSF: Conservation of mass First Law : No heat transfer, change in kinetic and potential energies are negligible

11. 2 – 3 : Boiler: Isobaric Heating : p3 = p2 QCV 3 2 No work transfer, change in kinetic and potential energies are negligible Assuming a single fluid entering and leaving…

12. 3 T 4 Turbine : Adiabatic Process :s4=s3 No heat transfer. Change in kinetic and potential energies are negligible Assuming a single fluid entering and leaving…

13. 4 – 1 : Condenser : Isobaric Cooling : p4 = p1 QCV 4 1 No work transfer, change in kinetic and potential energies are negligible Assuming a single fluid entering and leaving…

14. Layout of Equipment :The Simple Rankine Cycle

15. Analysis of Rankine Power Plant • First law for a Power Plant:

16. Cost to Benefit Ratio Analysis of Rankine Cycle

17. Cost to Benefit Ratio Analysis of Rankine Cycle

18. Heat Rate: An International Standard • The term “heat rate” simply refers to energy conversion efficiency, in terms of • “how much energy must be expended in order to obtain a unit of useful work.” • In a combustion power plant, the fuel is the energy source, and the useful work is the electrical power supplied to the grid. • Because “useful work” is typically defined as the electricity, engineers tend to work with the net plant heat rate (NPHR). • Units: kJ/kW-hr or kCal /kW-hr

19. Method of Calculation • Net Plant power output : Pnet in kW • Fuel consumption rate: mfuel kg/hr • Higher heating value or higher calorific value: HHV in kJ/kg Generation of most useful steam is first step in enhancing Pnet. Economics of Steam generation plays an importance….

20. Parametric Study of Rankine Cycle 6500C 6000C 5000C 4000C 3000C h P max

21. Parametric Study of Rankine Cycle 23.5MPa 22MPa 18MPa 10MPa 6MPa h 3MPa 1MPa Tmax

23. 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

24. Classification of Rankine Cycles