HEAT TRANSFER AT SUPERCRITICAL PRESSURES (SURVEY) 1

Transcription

1 HEAT TRANSFER AT SUPERCRITICAL PRESSURES (SURVEY) 1 Igor Pioro*, Hussam Khartail and Romney Duffey Chalk River Laoratories, AECL, Chalk River, ON, Canada K0J 1J0 Keywords: Supercritical pressure, forced convective heat transfer, water, caron dioxide. Ojectives The ojectives are to assess the work that was done in the area of heat transfer at supercritical pressures, to understand the specifics of heat transfer at these conditions, to compare different prediction methods for supercritical heat transfer in tues and undles, and to choose the most reliale ones. Preliminary Findings The exhaustive literature search, which included hundreds of papers, showed that the majority of correlations were otained in tues and just few of them in other flow geometries including undles. The use of supercritical steam-water in nuclear reactors (Generation IV Nuclear Energy Systems Report 2001) will: Significantly increase thermal efficiency up to 40 45%; Decrease reactor coolant pumping power; Lower containment loadings during loss-of-coolant accidents; Eliminate dryout; and Eliminate steam dryers, steam separators, re-circulation pumps, and steam generators. 1 The presentation is ased on the following papers: 1. Pioro, I.L., Khartail, H.F. and Duffey, R.B., Heat Transfer at Supercritical Pressures (Survey), Proceedings of the 11 th International Conference on Nuclear Engineering (ICONE-11), Shinjuku, Tokyo, Japan, April 20 23, 2003, Paper No , 13 pages. 2. Duffey, R.B., Khartail, H.F., Pioro, I.L. and Hopwood, J.M., The Future of Nuclear: SCWR Generation IV High Performance Channels, Proceedings of the 11 th International Conference on Nuclear Engineering (ICONE-11), Shinjuku, Tokyo, Japan, April 20 23, 2003, Paper No , 8 pages.

2 THERMOPHYSICAL PROPERTIES AT CRITICAL AND SUPERCRITICAL PRESSURES p=22.1 MPa p=25.0 MPa Density, kg/m

3 Specific Enthalpy, kj/kg p=22.1 MPa p=25.0 MPa

4 600 p=22.1 MPa p=25.0 MPa Specific Heat, kj/kg K

5 Volume Expansivity, 1/K p=22.1 MPa p=25.0 MPa

6 0.7 Thermal Conductivity, W/m K p=22.1 MPa p=25.0 MPa

7 Dynamic Viscosity * 10 5, Pa s p=22.1 MPa p=25.0 MPa

8 35 p=22.1 MPa p=25.0 MPa 30 Prandtl Numer

9 KRASNOSHCHEKOV AND PROTOPOPOV (1959, 1960) FOR TUBES = p p w w c c k k Nu Nu µ µ ). Re log. (. ) Pr (. Pr Re Nu = + = ξ ξ ξ w w k T T H H µ ) ( ) ( Pr = w w p T T H H c =.

10 DYADYAKIN AND POPOV (1977) FOR TIGHT 7-ROD BUNDLE WITH HELICAL FINS Nu x = Re 0.8 x Pr 0.7 x ρ w ρ 0.45 x µ µ in 0.2 x ρ ρ in 0.1 x D x hy

11 Heat Transfer Coefficient, kw/m 2 K Bulk Experiment (Shitsman, 1963) Correlation (Dittus-Boelter) Correlation (Shitsman, 1959) Correlation (Kondrat'ev, 1969) Correlation (Krasnoshchekov- Protopopov, 1960) Correlation (Ornatsky et al., 1970) Correlation for finned undle (Dyadyakin and Popov, 1977) Correlation (Bishop et al., 1964) Correlation (Kitoh et al., 1999) Water, circular vertical tue, D=8 mm, L=1.5 m, P=23.3 MPa, q=1084 kw/m 2, G=1500 kg/m 2 s, t pc =378.6 o C, H pc =2148 kj/kg Fluid Enthalpy, kj/kg Heated Length, m

12 Sheath Wall Goran' et al., 1990 Kondrat'ev, 1969 Krasnoshchekov-Protopopov, 1960 Dyadyakin-Popov, 1977 Bishop et al., 1964 Kitoh et al., 1999 Kirillov et al., 1990 CANDU-X Pressure 25 MPa, Mass flux 860 kg/m 2 s Heat flux 670 kw/m 2 Uniform axially and radially D hy =7.71 mm Heated length m 43-element undle 12 undles in string Bulk Fluid Temperature 400 Pseudocritical Temperature Heated Length, m

13 FINAL REMARKS AND CONCLUSIONS A comparison of various correlations for supercritical heat transfer showed that several correlations can e used for preliminary estimations of heat transfer in tues and undles. However, no one correlation is ale to descrie deteriorated heat transfer in tues. Preliminary calculations of heat transfer and temperature profiles in a CANDU- X supercritical water-cooled reactor operating conditions showed that the proposed concept of this reactor is feasile for future development.

14 CURRENT EXPERIMENTAL DATA FOR CO 2 LOOP (NORMAL HEAT TRANSFER) Caron dioxide, P out =8.36 MPa, P=1.5 kpa, G=726 kg/m 2 s, Q=1.5 kw, q=26.8 kw/m 2 (uniform heat flux) Fluid Bulk Enthalpy, kj/kg Inside wall temperature (recalculated from T w ext ) T in Heat transfer coefficient (calculated) HTC (Krasnoshchekov- Protopopov, 1960) cal Tpc = Bulk fluid temperature (calculated) T in, T out, T out mixer, T w ext are measured values Heated length Axial Location, mm o C T out T out mixer Heat Transfer Coefficient, W/m 2 K

15 (NORMAL, DETERIORATED AND IMPROVED HEAT TRANSFER) Caron dioxide, P out =8.37 MPa, P=1.7 kpa, G=823 kg/m 2 s, Q=12.0 kw, q=214.3 kw/m 2 (uniform heat flux) T in Fluid Bulk Enthalpy, kj/kg DHT, q/g= 0.26 kj/kg IHT Heat transfer coefficient (calculated) Inside wall temperature (recalculated from T w ext ) T in, T out, T out mixer, T w ext are measured values Bulk fluid temperature (calculated) Heated length cal Tpc = T out Axial Location, mm o C T out mixer Heat Transfer Coefficient, W/m 2 K