This modified Rankine power cycle involves three turbines, an open and a closed

Question

This modified Rankine power cycle involves three turbines, an open and a closed feed water preheater, a condenser, a boiler/superheater, two pumps and a throttle. The schematic is shown above and in the the text book on page 206 Figure 5.6. In this problem, all of the turbines and the pump between streams 5 and 6 are considered reversible. You should be able to do balances around them if were not ideal however. There are 18 parts to the problem but many of the steps should not take very long. The pressures and temperatures are given are P1= 10 MPa, P2= 4 MPa, P3= 2 MPa. T1= 538oC, T8= 215oC, T9= 300oC. Streams m2, m3,and m4 go into the top of the respective preheater/condenser. (a) What is P10(MPa)?

Explanation / Answer

P2 IS GIVEN AS 4MPa. THIS EXTRACTION STEAM FROM FIRST STAGE OF TURBINE IS SENT TO CLOSED FEED WATER PREHEATER TO PREHEAT BOILER FEED WATER. (NOTE: CLOSED PREHEATER MEANS WHERE STEAM & BOILER FEED WATER ARE NOT ALLOWED TO MIX WHEREAS OPEN PREHEATER ALLOWS MIXING OF STEAM & BOILER FEED WATER AS IN DEAERATOR). CYCLE MENTIONED IN QUESTION IS REGENERATIVE RANKINE CYCLE. STEAM USED IN PREHEATER A SHALL EITHER CONDENSE FULLY OR PARTIALLY. THEREFORE, ITS PRESSURE SHALL BE SAME AS INLET PRESSURE P2. THEREFORE, PRESSURE P10 IS 4MPa. ADDITIONALLY, ITS PRESSURE SHALL BE ET DOWN TO 2MPa (PRESSURE P11) WHICH IS EQUAL TO SECOND STAGE EXTRACTION STEAM PRESSURE.& ALLOWED TO MIX WITH CONDENSATE FROM CONDENSER.

THEREFORE, YOUR REQUIRED ANSWER IS PRESSURE P10= 4MPa.

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