Energy dissipation in an actual cogeneration plant

Assume that the kinetic and potential energy changes are negligible, and this is a steady-state process. The surroundings are at 540 R. 

In this cogeneration cycle, the steam extracted from the turbine is used in process heat. The liquid condensate from the process heat is combined with the output of the condenser 

From the energy balance around the mixer, we have rit hii =0.2  

Using the reference values for/To = 38.0 Btu/lb and S0 = 0.0745 Btu/(lb R) at 70°F, we estimate the exergy flows 4 = Hi —H0-T0(.S, S0) and ml Ar which are shown along with the other properties below. Table 4.8a shows the state properties of the cogeneration plant. The turbine work output is  

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Example 4.20 Energy dissipation in an actual cogeneration plant A cogeneration plant uses steam at 900 psia and 1000°F to produce power and process heat (see Figure 4.26). The steam flow rate from the boiler is 16 lb/s. The process requires steam at 70 psia at a rate of 3.2 lb/s supplied by the expanding steam in the turbine. The extracted steam is condensed and mixed with the water output of the condenser. The remaining steam expands from 70 psia to the condenser pressure of 3.2 psia. If the turbine operates with an efficiency of 80% and pumps with an efficiency of 85%, determine the work loss at each unit. 

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