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ORCNext – WP4Development of supercritical technologies

Catternan Tom

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ORCNext – WP4Development of supercritical technologies

Transcritical ORCs – Literature review

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Transcritical ORCs

• Best efficiency and highest power output when temperature profile of HS and WF match lower exergy destruction (Larjola et al.).

• Better thermal matching driving force LMTD↓ UA↑

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Screening criteria Cycle criteriaSafety (ASHRAE 34) Thermodynamic PIEnvironmental (GWP, ODP, ATL) Heat exchanger PIStability working fluid Cost PICompatibility with materialsThermophysical propertiesAvailability and cost

Selection of working fluids

• Wide range of applications and ranges no consensus for best working fluid.

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Selection of working fluidsPhysical data Safety data Environmental data

Name Type Tcrit (°C) pcrit (bar)Molecular

weight (g/mol)ASHRAE 34

safety group ATL (yr) ODPGWP

(100 yr)HFC-23 Wet 26,14 48,30 70,01 A1 270 0 14800R-747 (CO2) Wet 31,10 73,80 44,01 A1 >50 0 1HFC-125 Wet 66,02 36,20 120,02 A1 29 0 3500HFC-410A - 70,20 47,90 72,58 A1 16,95 0 2088PFC-218 Isentropic 71,89 26,80 188,02 A1 2600 0 8830HFC-143a Wet 72,73 37,64 84,04 A2 52 0 4470HFC-32 Wet 78,11 57,83 52,02 A2 4,9 0 550HFC-407C - 86,79 45,97 86,20 A1 15657 0 1800HFC-134a Isentropic 101,03 40,56 102,03 A1 14 0 1430HFC-227ea Dry 101,74 29,29 170,03 A1 34,2 0 3220PFC-3-1-10 Dry 113,18 23,20 238,03 - 2600 0 8600HFC-152a Wet 113,50 44,95 66,05 A2 1,4 0 124PFC-C318 Dry 115,20 27,78 200,03 A1 3200 0 10250HFC-236ea Dry 139,22 34,12 152,04 - 10,7 0 1370PFC-4-1-12 Dry 147,41 20,50 288,03 - 4100 0 9160HFC-245fa Isentropic 154,05 36,40 134,05 B1 7,6 0 900HFC-245ca Dry 174,42 39,25 134,05 A1 6,2 0 693

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Heat exchanger design

Influence ORC parameters on HX design (Schuster and Karellas, 2012)• R134a, R227ea and R245fa• Jackson correlation (1979): Water and CO2

• HTC decreases with increasing supercritical pressure and temperature HX area increases

• Relatively unknown heat transfer mechanisms around C.P. need further investigation

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ORCNext – WP4Development of supercritical technologies

Forced convective heat transfer at supercritical pressuresLiterature review

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Supercritical state

• Critical point ‘c’• Supercritical state• For T>Tcrit Continuous transition from liquid-like fluid to gas-

like fluid (no phase change)

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Thermophysical properties

• (cp, , m r, l, Pr…)=f(T)• Pseudo-critical temperature Tpc= f(p)

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Thermophysical properties

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Literature overview

• Experimental– H2O, CO2, nitrogen, hydrogen, helium, ethane, R22– Uniform cross section

• Circular• Recently: triangular and square

– Uniform heat flux electrically forced Tw

– Different experimental results• Numerical– Only recent

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General characteristicsHeat transfer enhancement

Maximum HTC

• ↓• ↑• Due to variation of

thermophysical properties

(1) Theory (∆) Experimental: = 140±4.4 kg/h; q = 1.44 W/cm²

(2) Theory(x) Experimental: = 140±3.1 kg/h; q = 2.73 W/cm²

(3) Theory (○) Experimental: = 280±5.6 kg/h; q = 3.32 W/cm²

(4 Theory (●) Experimental: = 280±7.8 kg/h; q = 5.20 W/cm²

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.

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General characteristicsHeat transfer deterioration

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 direction1 382 27 Vertical upward2 382 37 Vertical upward3 400 45 Vertical upward4 375 52 Vertical upward5 400 27 Vertical downward6 400 36 Vertical downward7 393 43 Vertical downward8 381 50 Vertical downward

Upward flow Downward flow

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General characteristicsHeat transfer deterioration

Temperature distribution as a function of local bulk enthalpy along heated vertical and horizontal pipes (1.6 cm diameter) for water at 245 bar (= 1.11 pcrit): and

• 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

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Influence of parameters

• Heat flux

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.

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Influence of parameters

• Heat flux • Mass flow

Generalized curves for water at 250bar (Lokshin et al.)

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Influence of parameters

• Heat flux • Mass flow • Flow direction

Comparison of heat transfer between an upward and downward flow for CO2 by Jackson and Evans-Lutterodt

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Influence of parameters

• Heat flux • Mass flow • Flow direction• Pipe diameter

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

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Correlations• 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.)

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ORCNext – WP4Development of supercritical technologies

Goals and planning for the next 6 months

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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

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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

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Thank you for your attention.