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1 ORCNext – WP4 Development of supercritical technologies Catternan Tom 1

2 ORCNext – WP4 Development of supercritical technologies Transcritical ORCs – Literature review 2

3 Transcritical ORCs Best efficiency and highest power output when temperature profile of HS and WF match  lower exergy destruction (Larjola et al.). 3 Better thermal matching  driving force LMTD↓  UA↑

4 Screening criteriaCycle criteria Safety (ASHRAE 34)Thermodynamic PI Environmental (GWP, ODP, ATL)Heat exchanger PI Stability working fluidCost PI Compatibility with materials Thermophysical properties Availability and cost Selection of working fluids Wide range of applications and ranges  no consensus for best working fluid. 4

5 Selection of working fluids 5 Physical dataSafety dataEnvironmental data NameTypeT crit (°C)p crit (bar) Molecular weight (g/mol) ASHRAE 34 safety groupATL (yr)ODP GWP (100 yr) HFC-23Wet26,1448,3070,01A1270014800 R-747 (CO 2 )Wet31,1073,8044,01A1>5001 HFC-125Wet66,0236,20120,02A12903500 HFC-410A-70,2047,9072,58A116,9502088 PFC-218Isentropic71,8926,80188,02A1260008830 HFC-143aWet72,7337,6484,04A25204470 HFC-32Wet78,1157,8352,02A24,90550 HFC-407C-86,7945,9786,20A11565701800 HFC-134aIsentropic101,0340,56102,03A11401430 HFC-227eaDry101,7429,29170,03A134,203220 PFC-3-1-10Dry113,1823,20238,03-260008600 HFC-152aWet113,5044,9566,05A21,40124 PFC-C318Dry115,2027,78200,03A13200010250 HFC-236eaDry139,2234,12152,04-10,701370 PFC-4-1-12Dry147,4120,50288,03-410009160 HFC-245faIsentropic154,0536,40134,05B17,60900 HFC-245caDry174,4239,25134,05A16,20693

6 Heat exchanger design Influence ORC parameters on HX design (Schuster and Karellas, 2012) R134a, R227ea and R245fa Jackson correlation (1979): Water and CO 2 HTC decreases with increasing supercritical pressure and temperature  HX area increases Relatively unknown heat transfer mechanisms around C.P.  need further investigation 6

7 ORCNext – WP4 Development of supercritical technologies Forced convective heat transfer at supercritical pressures Literature review 7

8 Supercritical state Critical point ‘c’ Supercritical state For T>T crit  Continuous transition from liquid-like fluid to gas-like fluid (no phase change) 8

9 Thermophysical properties (c p, ,, Pr…)=f(T) Pseudo-critical temperature  T pc = f(p) 9

10 Thermophysical properties 10

11 Literature overview Experimental – H 2 O, CO 2, nitrogen, hydrogen, helium, ethane, R22 – Uniform cross section Circular Recently: triangular and square – Uniform heat flux  electrically  forced T w – Different experimental results Numerical – Only recent 11

12 General characteristics Heat transfer enhancement 12 Variation of the heat transfer coefficient with bulk temperature for forced convection in a heated pipe for carbon dioxide of 78.5bar flowing upwards in a 1.0 diameter vertical pipe.

13 General characteristics Heat transfer deterioration 13 Wall and bulk temperature as a function of the distance along a vertical heated 1.6 cm diameter pipe for water at 245 bar (1.11 pcrit). Comparison upward and downward flow – Downward  no unusual behaviour – Upward  deterioration Flow direction 138227Vertical upward 238237Vertical upward 340045Vertical upward 437552Vertical upward 540027Vertical downward 640036Vertical downward 739343Vertical downward 838150Vertical downward Upward flowDownward flow

14 General characteristics Heat transfer deterioration 14 Comparison upward, downward and horizontal flow (1) Horizontal pipe – upper surface (2) Horizontal pipe – lower surface (3) Vertical pipe – upward flow (4) Bulk fluid temperature

15 Influence of parameters 15 Left: Ratio of the experimental heat transfer coefficient to the value calculated via the Dittus-Boelter equation;. Right: Wall temperature behaviour for low and high heat fluxes.

16 Influence of parameters 16 Generalized curves for water at 250bar (Lokshin et al.)

17 Influence of parameters 17 Comparison of heat transfer between an upward and downward flow for CO 2 by Jackson and Evans- Lutterodt

18 Influence of parameters 18 Effect of tube diameter on heat transfer coefficient (Cheng X. et al.)

19 Correlations 19 Bringer and Smith (1957) Miropolsky and Shitsman (1959, 1963) Petukhov, Krasnoshchekov and Protopopov (1959, 1961, 1979) Domin (1963) Bishop (1962, 1965) Kutateladze and Leontiev (1964) Swenson (1965) Touba and McFadden (1966) Kondrat’ev (1969) Ornatsky et al. (1970) Yamagata (1972) Yaskin et al. (1977) Jackson (1979) Yeroshenko and Yaskin (1981) Watts (1982) Bogachev et al. (1983) Griem (1995, 1999) … Heat transfer coefficient for supercritical water according to different correlations (Cheng X. et al.)

20 ORCNext – WP4 Development of supercritical technologies Goals and planning for the next 6 months 20

21 Transcritical ORCs Finish literature study (± 10 more papers to read) Model sub – and transcritical cycle (together with WP1) – Choose parameter range – Compare both cycles using the Performance Indicators for several working fluids – Check influence of the variable parameters on the objective functions  sensitivity – Make a list of 3 working fluids, which will be used in the experimental setup 21

22 Supercritical forced convection heat transfer Investigate thermophysical properties under supercritical conditions of the selected working fluids (via REFPROP or EES) Finish literature study – Deteriorated and improved heat transfer regimes – Onset deterioration – Correlations Fundamental understanding heat transfer and occurring flow -  Test setup have to be built: – Prepare setup – Choose materials – Order 22

23 Thank you for your attention. 23

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