Chapter $8$: Vapour Power and Refrigeration Cycles

$221$

Problem $6$: A steam power plant operating on a non$-$ideal Rankine cycle is used to generate power, as shown in the diagram. The steam$/$water flow rate in the Rankine cycle is $1\mathrm{.}5k\frac{g}{s}.$ The boiler is heated by a hot oil stream. The oil has a constant specific heat of $1\mathrm{.}9kJk{g}^{-1}{K}^{-1}.$ The condenser is cooled by a cooling water stream. The temperature of the surroundings may be assumed to be $25C.$ Determine:

a$)$ The power input to the pump $($kW$).-10\mathrm{.}28$ kw

b$)$ The power output by the turbine $($kW$).1193\mathrm{.}3$ S

c$)$ The mass flow rate of oil flowing through the boiler $(k\frac{g}{s})\mathrm{.}15\mathrm{.}52k\frac{g}{s}$

d$)$ The mass flow rate of water flowing through the condenser $(k\frac{g}{s})\mathrm{.}38\mathrm{.}76k\frac{g}{s}$

e$)$ The thermal efficiency of the Rankine cycle. $26\mathrm{.}7\%$

f$)$ The entropy change of the oil stream $(k\frac{W}{K}).-5\mathrm{.}558k\frac{w}{K}$

g$)$ The entropy change of the water stream $(k\frac{W}{K})10\mathrm{.}52K\frac{w}{K}$

h$)$ The entropy generation rate for the Rankine cycle $($kW$/$K$)-4\mathrm{.}962k\frac{W}{k}$

i$)$ The second law efficiency of the Rankine

cycle. $44\mathrm{.}4\%.$

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