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Task 3 (25 points) The combined heat and power plant (CHP, states 6 to 8) shown below is operated with fuel B at ambient conditions pu = 1 bar and tu = 5°C. The usable waste heat from the CHP unit (Q1 + QG) is fed to a steam turbine process with organic working medium. (ORC: Organic Rankine Cycle, states 1 to 5). The engine output of the CHP PBHxw = 2.88 MW and the turbine output Pr of the ORC process are transferred to a generator. PBHKW تقضي 0 4 10 Motor and3 Heat exchanger Heat exchanger - Pump Turbine Heat exchanger 1 mo RC Q Ab Changes in condition 12: Irreversible adiabatic pressure increase of the working medium with mass flow MRC from state 1 (p = 0.96 bar) to state 2 (p2 = 7.20 bar). 2 3: Isobaric heating of the working medium with the waste heat flow Q1 = 1.72 MW of the CHP engine up to state 3 (liquid at even boiling point). The heat exchanger is adiabatic to the outside. 34: Isobaric evaporation of the working medium with the waste heat flow Quc. of the CHP exhaust gas to state 4 (just fully evaporated). The heat exchanger is adiabatic to the outside and a temperature difference of AT4,8 = 100 K is set between states 4 and 8. 4- 5:Irreversibleadiabatic expansion of the working medium in the turbine with the isentropic efficiency ns = 0.85 to state 5 (p = p.). 5 1:Isobariccondensation of the working medium up to state 1 (just fully liquefied). 67: Combustion of fuel B (r = 0.24 kg/s) in the CHP engine with the calorific value AV hu = 50.4 MJ/kg (waste heat flow @r is used by the ORC process). 78: Isobaric cooling of the CHP exhaust gas (ING = 4 kg/s) from state 7 (t = 840 ) to state 8 (waste heat flow QG is transferred from the ORC-. process). The exhaust gas is to be regarded as an ideal gas and its htcapacity is constant in the temperature range under consideration with CpAg = 1.1143 kJ/(kg K).

TOOS Sciences a) crit. crit. Point crit Point Point AAA 3 SL /TL s Substance data organic working medium Two-phase pth' s!! bar CkJ/kg kJ/kg kJ/(kg K) kJ/(kg K) 0.96 25.54 227.52 646.68 0.9209 2.3436 7.20 109.98 435.00 778.44 1.5468 2.4888 Single-phase pth S bar-CkJ/kg kJ/(kg K) 0.7198 0.96 0.00 170.40 0.96 24.00 224.28 0.9084 0.96 48.00 685.20 2.4708 0.96 72.00 728.28 2.6040 0.96 96.00 2.7360 773.40 820.68 0.96 120.00 2.8656 0.96 144.00 870.00 2.9952 7.20 0.00 171.00 0.7183 7.20 24.00 224.88 0.9068 7.20 48.00 280.44 1.0898 7.20 72.00 1.2684 338.16 398.52 7.20 96.00 1.4448 7.20 120.00 799.92 2.5476 7.20 144.00 852.24 2.6844

Notes: Please give results for entropy and mass flows to four decimal places (e.g. 6.3567), and all other results to two decimal places (e.g. 0.01 or 9.87 or 242.00)! [2 P] [1 P] a) Determine the evaporation and condensation temperature (in K) of the working medium in the ORC process. b) Determine the temperature (in K) of the CHP exhaust gas emitted to the environment (condition 8). c) is state point 5 in the homogeneous region or two-phase region? Explain this on the basis of the entropy. d) Justify which of the three given T, s diagrams corresponds to the above. The ORC process described in the report is qualitatively correct. e) Determine the enthalpy (in kJ/kg) of states 1, 3, 4 and 5. [1.5 P] [3 P] [5 P] Use only the following enthalpy values for the following parts of the task: 1 3 4 5 State points h/kJ/kg 251 479 857 775 f) Determine the mass flow rate of the ORC process narc (in kg/s). [5 P] Use only the mass flow rate NRC = 8.18 kg/s for thollowing parts of the task. g) Determine the enthalpy (in kJ/kg) of state 2. [3 P] Use only the enthalpy h2 = 280 kJ/kg for the following parts of the task. h) Determine the pump and turbine power in kW) . [2P] Only use the following services and blows for the following parts of the task: IPBHK WI IPP 1 IP 1 IQ Q MI AGI 3089 kW 2880 261 738 1720 i) Determine the percentage exergetic efficiency of the total pores (CHP+ORC). [2.5 P] Notes: The pump is driven by the turbine. The exergetic expenditure is given by the calorific value. 7