Question

Water is the working fluid in an ideal regenerative Rankine cycle with one open feed water heater, Figure 2. Upstream of the high pressure turbine superheated vapour with a mass flow rate of 90 kg/s entres the first-stage turbine at a pressure of 14 MPa Each turbine stage has an isentropic efficiency of 90%. The temperature of the inlet vapour is 520°C. The steam expands through the first-stage turbine to a pressure of 0.9MPa where some of the steam is extracted and diverted to an open feed-water heater. The operating pressure of the feed-water heater is 0.9 MPa. The remaining steam is expanded through a second-stage turbine to a condenser where the pressure is 6 kPa. It is assumed that saturated liquid exits the feed-water heater at 900 kPa and each pump has an efficiency of 90%. Given that the turbine power can be calculated using equation 1, where (y) is a fraction of a unit mass flow: Wmllhi - h2) +(1 -y)h -h) Equation 1 Sleam generator Condenser Open feedwater heater . Pump 2 Pump p2 Figure 2, Regenerative Rankine Cycle a) Draw and label the corresponding TS diagram for Figure 2, with the unit mass and mass fraction flow labelled between the open feed-water heater and the low pressure turbine/condenser circuit. [4 Marks] b) Determine: (i) The net power developed, in kW. 5 Marks] (i) The rate of heat transfer to the steam passing through the boiler, in kW [3 Marks] (ii) The thermal efficiency [3 Marks] (iv) The mass flow rate of condenser cooling water, in kg/s, if the cooling water undergoes a temperature increase of 16°C with negligible pressure change passing through the condenser. 15 Marks]

Answer 1

7 75 T4 (l-y) 3S 3 4- State A lempe line Ti=520c Supef haaed vapout Bom super heated tablo h-3376 午KJ1kq foom suupet heatad toblo» second stage tribuni -23-35 balwn Exit stati-as s-..SJ- = 6.4584 T35- 0- 76

has- hfs t Xs*hfß, @ 6kP - i51-5 +0-76 (24Ib) 1488 22K3lk9 Statt 4 ud at GkPa 15(-5 t D.001006 (0.9 10-6) = 15 2.3 4 Kalka P- 55S-h4 -o-q* 152-34 -151-5 h5 - h4 5-151- h? - 152-43Kjlk9 he - 74-2 6 K3ltg 3 7426 + 0.001121 (14x10-о-љао s h7 - 742-b

2376-14-hi hi-hi 3376-74- - 1488-22 3 - 2127-012 Kjlka By eneigy bolane ui the open fread wates healos 2 h6 open feed wtrs hoatel T4-2-I52-43 2815.C74-1S2.43 a) The net powei davelsped,

97810-135 Kw ol(i - o-216)(I52-43 -15i-5) +- CTSa - 7+2-6 1541.56 kw Wnet- - 47870. 1S1.56 Wre 96328-57 kw 235 596.6 kw a6328 .57 ー0.4088 235596.-6 4088 ท่าเ