2013-3-6 The Rankine Cycle Engineering model: Each component is analyzed as a control volume at steady state. The turbine and pump operate adiabatically. Kinetic and potential energy changes are ignored. The Rankine Cycle Applying mass and energy rate balances Turbine 盘内 (Eq8.) Condenser 一内 (Eg.8.2) Pump 臣友内 (E4.8.3) Boiler 会A内 (Eq.8.4) 1
2013-3-6 11 The Rankine Cycle ►Engineering model: ►Each component is analyzed as a control volume at steady state. ►The turbine and pump operate adiabatically. ►Kinetic and potential energy changes are ignored. Turbine Condenser Pump Boiler The Rankine Cycle 4 3 p h h m W = − & & 1 2 t h h m W = − & & 1 4 in h h m Q = − & & (Eq. 8.3) (Eq. 8.4) (Eq. 8.2) (Eq. 8.1) 2 3 out h h m Q = − & & ►Applying mass and energy rate balances
2013-3-6 The Rankine Cycle Performance parameters Thermal Efficiency _m-/m么-4)--h (Eq.8.5a en/rit (h-h) Back Work Ratio( Back work ratio is characteristically ow for vapor power plants.For instance,in Example 8.1,the power required by the pump is less than 1%of the power developed by the turbine. The Rankine Cycle Provided states 1 through 4 are fixed,Egs 8.1 through 8.6 can be applied to determine performance of simple vapor power plants adhering to the Rankine cycle. Since these equations are developed from mass and energy balances,they apply equally when irreversibilities are present and for idealized performance in the absence of such effects. 12
2013-3-6 12 Thermal Efficiency The Rankine Cycle ( ) ( ) / / bwr 1 2 4 3 t p h h h h W m W m − − = = & & & & (Eq. 8.6) (Eq. 8.5a) ►Performance parameters ( ) ( ) ( ) / / / 1 4 1 2 4 3 in t p in cycle h h h h h h Q m W m W m Q W − − − − = − = = & & & & & & & & η Back Work Ratio Back work ratio is characteristically low for vapor power plants. For instance, in Example 8.1, the power required by the pump is less than 1% of the power developed by the turbine. The Rankine Cycle ►Provided states 1 through 4 are fixed, Eqs. 8.1 through 8.6 can be applied to determine performance of simple vapor power plants adhering to the Rankine cycle. ►Since these equations are developed from mass and energy balances, they apply equally when irreversibilities are present and for idealized performance in the absence of such effects