Question

Problem #2 (30 The steam cycle described in Problem #1 wasted a significant amount of exergy to the cooling water. A real cycle might cascade the energy down to a lower temperature cycle to utilise some of this exergy (regeneration). It might also use the heat to execute an industrial process (cogeneration). The cycle described below does both! inSeam generator Turbine 1.5 bar H20 cycle To industrial process H2OR-134a heat exchanger Turbine Refrigerant cycle R-134a cycle Pump Condenser Pump Return flow from industrial process I bar, 60°C P2 Shown is a schematic diagram for a co-generation cycle. In the steam cycle, superheated vapour enters that turbine at 2 kg/s at 80 bar, 600°C, and expands isentropically to 1.5 bar 25% of the flow is then extracted for industrial process heating. The rest of the steam passes through a heat exchanger, which serves as the boiler of the R-134a cycle and the condenser of the steam cycle. The condensate leaves the heat exchanger as a saturated liquid at 1 bar where it is combined with the return flow from the process, at 60°C and 1 bar, before being pumped isentropically to the steam generator pressure. The R-134a cycle is an ideal Rankine cycle with refrigerant entering its turbine at 16 bar, 80°C, and saturated liquid leaving the condenser at 6 bar. Determine, in kW, a) the rate of heat transfer to the working fluid passing through the steam generator of the steam cycle b)the net power output of the binary cycle c) the rate of heat transfer to the industrial process

Answer 1

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一2

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6 So W ー(·23 2136 kW e c