1. SAL College Of Engineering Opp: Science city, Near Bhadaj, A’bad. Subject:-EngineeringThermodynamics (2131905) 131130119091 Kaushik Santoki 131130119092 Manthan Shah 131130119093 Neer Shah 131130119094 Priyansh Shah 131130119095 Raj Shah Topic:- Comparision of carnot cycle & Rankine Cycle Gudid by :- Asst. Proff Yahadeepsinh Jadeja

2. Comparison of carnot and rankine Cycles The carnot cycle has the maximum possible efficiency for the given temperature limits but it is not suitable in steam power plants. The reversible adiabatic expansion in the turbine, the constant temperature heat rejection in the condenser, and the reversible adiabatic compression in the compressor/pump, are similar characterstic features of both the rankine and carnot cycles. The heat addition process in the rankine cycle is reversible and at constant pressure, in the carnot cycle, it is reversible and isothermal

3. The exhaust steam from the turbine is not completely condensed in condenser in case of carnot cycle, while in case of rankine cycle it is completely condensed.

4. The compressor is used in carnot cycle to handle mixture of water and steam, while in Rankine cycle pump is used to handle water. Consider two carnot cycles in fig, have the same thermal efficiency but since carnot cycle efficiency is grater than rankine cycle efficiency. But the carnot cycle can not be the realized in practice because the compressor work in both the cycle is very large. Superheating of seam is very difficult to achieve in carnot cycle but there is a possibility of superheating. The work ratio is very high in rankine cycle compared to carnot cycle since the pump work is very small compared to compression work in case of carnot cycle.

5. Affecting parameter of rankine cycle

6. 1. Effect of superheating of steam Rankine cycles (1-2-3-4-1) and (1-2’-3’-4-1) using dry saturated steam and super heated steam respectively are shown in fig. It is obvious from the fig. that super heat cycle delivers more work by an amount equal to the shaded area (2-2’-3’-3-2). The heat supply to steam is also increased by an amount equal to area under the curve (2-2’). However the ratio of increase in work output to increase in heat supply to steam is more than the ratio of work done to heat supply for rankine cycle (1-2-3-4-1).Due to with the cycle efficiency increases. Due to the super heating steam the average temperature of heat addition to the cycle increases while the avg. temp. of heat rejection from the cycle remain the same.

7. 2.Effect of increasing boiler pressure

8. Rankine cycle (1-2-3-4-1) and (1’-2’-3’-4-1’) have the same maximum temp. T2’. But Different maximum pressure p1 and p1’ respectively are shown in fig. The condenser pressure P2 is same in both cases. It is obvise from the fig. that due to increase in maximum pressure from P1 to P1’. The net work increase by area shown by the oblique hatching and decrease by the area shown by horizontal hatching due to the increased pressure of the cycle. This two work done are approximately the same but the heat rejection in the condenser decreases by the area (3-3’-M-L-3’) since heat rejection is reduse in the case of increasing boiler pressure. So the rankine efficiency increases.

9. 3.Effect of condenser pressure

10. In fig. two rankine cycle (1-2-3-4-1) at condenser pressure P4 and the cycle (1’-2-3’-4’-1’) with reduse condenser pressure P4’ have the same boiler pressure and Temp. Net work done is increased by the area (4’-1’-1-4-3-3’-4’) due to the reduse condenser pressure and the heat supplied during the cycle increases by the area (L-1’-M).

11. Thank You