Andreasen, Jesper Graa

Gabrielli, Paolo

Haglind, Fredrik

Pierobon, Leonardo

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 20, 2017Performance of ORC turbogenerators using zeotropic mixturesGabrielli, Paolo ; Andreasen, Jesper Graa; Pierobon, Leonardo; Haglind, FredrikPublication date:2014Link back to DTU OrbitCitation (APA):Gabrielli, P., Andreasen, J. G., Pierobon, L., & Haglind, F. (2014). Performance of ORC turbogenerators usingzeotropic mixtures. Poster session presented at  ASME Turbo Expo 2014, Düsseldorf, Germany.ii “poster” — 2014/6/27 — 15:45 — page 1 — #1 iiiiiiPerformance of ORC turbogeneratorsusing zeotropic mixturesPaolo Gabrielli1,*, Jesper Graa Andreasen2, Leonardo Pierobon2, FredrikHaglind21 University of Bologna, Department of Industrial Engineering, Viale del Risorgimento 2, 40136, Bologna, Italy* Corresponding author, Tel.: +39 340 484 9646, Email: paul.gabrielli89@gmail.com2 Technical University of Denmark, Department of Mechanical Engineering, Nils Koppels Allé, Building 403, 2800 Kgs. Lyngby, Denmark1 MOTIVATIONThe performance of organic Rankine cycle(ORC) power units (see Figures 1 and 2)strongly relates with the working fluid se-lection and the expander design. Binaryzeotropic mixtures have the potential to en-hance the system performance. However, theeffects of the mixture composition on the ex-pander efficiency need to be calculated soas to realistically assess the benefits of theaforementioned fluids.2pumpcondensergenerator31evaporator4coolantwaterturbineFigure 1: Layout of the ORC turbogenerator. The heat source isgeothermal water at 120 C.§3403060901201500.5 1 1.5 2 2.5Temperature [°C]Entropy [kJ kg-1 °C-1]Figure 2: Saturation curve of an isobutane/isopentane mixture in aT   s diagram, showing the thermodynamic cycle statepoints for the ORC unit.2 METHODThe study aims at assessing the impact ofthe composition of an isobutane/isopentanemixture on both the thermodynamic cycle per-formance and the expander efficiency.Such task is accomplished by coupling anORC simulator with a one-dimensional com-putational tool capable of designing multi-stage axial turbines. The case study is ageothermal heat source providing liquid wa-ter at 120C [1].3 RESULTSThe results suggest a certain influence ofthe mixture composition on the turbine perfor-mance.0.840.860.880.90.920 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Isentropic efficiency [-]Composition [moli-butane/mol]Figure 3: Isentropic efficiency at different mixture compositions.Figure 3 shows the optimized isentropic ef-ficiency profile which exhibits one absolutemaximum and minimum at the extremes ofthe plot (90.0% for pure isopentane and88.3% for pure isobutane).isobutan/ipentane Mass fraction Mole fraction T in [K] P in [kPa] P out [kPa] m [kg/s] W NET [kW] W NET [kWP ratio eta s S cond simulation with abstol=1e-4Pure ipentane 0 0 344.128849 365.470411 90.1842928 39.6354831 1540.66931 1736.403 4.052484 0.901 0.9001 00.082156023 0.1 346.300079 416.172857 100.048887 40.6088551 1636.98557 1839.055 4.159695 0.8954 0.8971 0.10.167635698 0.2 349.320049 485.967268 122.954962 40.2729607 1593.92927 1791.48 3.952401 0.8961 0.8972 0.20.25664488 0.3 351.308013 555.724531 145.492054 40.1848621 1574.9817 1765.129 3.819621 0.8964 0.8944 0.30.349406779 0.4 352.429973 626.091912 167.770347 40.2979092 1572.39291 1759.976 3.731839 0.8909 0.893 0.40.446163835 0.5 352.781644 697.696063 189.899865 40.5943584 1582.1302 1765.961 3.674021 0.8911 0.8903 0.50.547179827 0.6 352.413745 771.212087 211.990741 41.075269 1602.07492 1783.443 3.637952 0.889 0.8877 0.60.652742282 0.7 351.345159 847.423836 234.153939 41.757587 1631.25285 1811.481 3.619089 0.8885 0.8853 0.70.763165201 0.8 349.610505 928.138089 256.844715 42.6454433 1667.73873 1852.648 3.613616 0.8858 0.8854 0.80.878792185 0.9 347.594093 1023.98497 287.235499 43.4901208 1678.54034 1859.999 3.564967 0.8841 0.8833 0.9Pure isobutan 1 1 345.899938 1154.064 345.578906 43.9130028 1589.928 1763.996 3.339509 0.8843 0.8831 11000150020000 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Power [kW] Mole fraction (isobutane) Net power Net power0.880.8850.890.8950.90.9050 0.2 0.4 0.6 0.8 1 1.2Series10.840.860.880.90.920 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Isentropic efficiency [-] Composition [moli-butane/mol] 150016001700180019000 0.2 0.4 0.6 0.8 1Net power output [kW] Composition [moli-butane/mol] calculated turbine efficiencyconstant turbine efficiencyFigure 4: Organic Rankine cycle net power output at different mix-ture compositions.Figure 4 connects the net power output of theORC power module with the mixture compo-sition for calculated (red line) and constant(blue line) turbine efficiency (i s = 0:8). Thedifference in the power output maxima de-creases owing to the tendency of the ex-pander performance. The trend can be ex-plained by analysing the losses within theturbine [2]. The profile losses are the majorresponsible for the efficiency drop. The profileloss in the rotor presents a minimum at a mo-lar composition equal to 0.0 and a maximumwith pure isobutane, see Figure 5.00.010.020.030.040.050.060 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Efficiency loss [-]Composition [moli-butane/mol]Nozzle profile lossNozzle secondary lossRotor profile lossRotor secondary lossFigure 5: Profile and secondary losses at different mixture compo-sitions.4 CONCLUSIONSThis w rk demonstrates the importance ofembedding simulation tools for turbine de-sign in the thermodynamic cycle calculationwhen using binary mixtures as working flu-ids in ORC power units. Results unveil adeviation in the ORC net power output fordifferent mixture compositions when employ-ing the constant and the calculated turbineefficiency.5 REFERENCES[1] Heberle, F., Preißinger , M., Brüggemann,D. (2012). Zeotropic mixtures as workingfluids in Organic Rankine Cycles for low-enthalpy geothermal resources. RenewableEnergy, 37, 364 - 370.[2] Craig, H. R. M., & Cox, H. (1971). Per-formance estimation of axial flow turbines.Proceedings Institution of Mechanical Engi-neers, 71, 185 - 232.

Performance of ORC turbogenerators using zeotropic mixtures

http://orbit.dtu.dk/ws/files/97082598/Performance_of_ORC.pdf

Performance of ORC turbogenerators using zeotropic mixtures

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology