Experimental Study of the Transition from Forced to Natural Circulation in EBR-II at Low Power and Flow

Gillette, J.L.; Singer, R.M.; Tokar, J.V.; Sullivan, John E.

doi:10.1115/1.3244335

Cited by 10 publications

(5 citation statements)

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“…Thus increased power levels increase the peak coolant temperature, but simultaneously the larger axial temperature rise increases the bulk convective flow due to the increased buoyancy of the hotter, less dense fluid. Similar results have been reported by Gillette et al (1979) for actual in-reactor tests.…”

Section: Steady-state Natural Circulation Test Resultssupporting

confidence: 91%

Investigation of combined free and forced convection in a 2 x 6 rod bundle during controlled flow transients

Bates¹,

Khan²

1980

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An experimental study was performed to obtain local fluid velocity and temperature measurements in the mixed (combined free and forced) convection regime for specific flow coastdown transients. A brief investigation of steady-state flows for the purely free-convection regime was also completed. The study was performed using an electrically heated 2 x 6 rod bundle contained in a flow housing. In addition a transient data base was obtained for evaluating the COBRA-We thermal-hydraulic computer program (a modified version of the COBRA-IV code).The objective of the study was to develop an understanding of the thermalhydraulic phenomena at low flows in a rod bundle subjected to lateral power skews. Test conditions included 500-, 300-, 150-and 45-second flow coastdown transients, a Reynolds number range of -90 to -1300, and power skews of 1:0, 2:1, 3:1, and 4:1. The dimensionless group Gr*/Re 2 , which represents the ratio of buoyancy to inertial forces, was varied in the range 0.0 to 2.4 at selected lateral power skews. Flow recirculation zones were detected in the bundle during transient conditions at large ratios of buoyancy to inertial forces as indicated by the measurements of downward flow in the colder subchannels and upward flow in the hotter subchannels. No flow recirculation was detected in the bundle at steady-state conditions except at extremely low Reynolds numbers where heat loss and/or hydraulic effects of the discharge geometry become important. The length of the recirculation zone in the axial direction was observed to be dependent on rod power level, the lateral power skew, and the total flow rate.The data were compared to predictions obtained with the COBRA-We computer code. COBRA-We satisfactorily predicted the measured bundle subchannel velocity and temperature histories. At Reynolds numbers below 450 an improvement in the turbulent mixing model in COBRA-We was required to satisfactorily predict experimental results. This improvement was necessary because as the magnitude of the buoyancy forces increased, thermal plumes grew laterally as they moved axially upward. When adjacent thermal plumes interacted, turbulence was v generated which appeared to promote lateral mlxlng between subchannels. A model incorporating the enhanced turbulent mixing due to the thermal plume interactions was used to improve the COBRA-We predictions at large ratios of Gr*/Re 2 . The enhanced turbulent mixing parameter was correlated as a function of Grashof and Reynolds numbers (Gr/Re 2 ) and the ratio of local heat generating rate to the bundle average heat generation rate.vi ACKNOWLEDGMENTS

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Section: Steady-state Natural Circulation Test Resultssupporting

confidence: 91%

Investigation of combined free and forced convection in a 2 x 6 rod bundle during controlled flow transients

Bates¹,

Khan²

1980

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“…The solutions (8) and (11) are used now to integrate equation (6), where the density is written as p = p e [1 -/? (T -T £ )]:…”

Section: Steady-state Motionsmentioning

confidence: 99%

“…However, recent work on nuclear applications of thermosyphons is mainly concerned with transient behavior and stability of liquid metal fast breeder reactor loops (LMFBRs), cf. [8][9]. 2 Simple loops have also been studied in order to better understand basic phenomona in thermosyphons.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Analytical Investigation of a Natural Circulation System with Parallel Loops

Zvirin

Jeuck

Sullivan

et al. 1981

Journal of Heat Transfer

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A theoretical and experimental study of a natural circulation loop is presented. The analysis is based on a one-dimensional model in which the continuity, momentum, and energy equations are given and solved. Expressions for the steady-state and transient flow rates and temperature distributions are derived. The apparatus consisted of an electricallyheated section and two parallel loops with heat exchangers. Steady-state and transient experiments were conducted to study the effects of core flow resistance, power distribution and upper plenum design. Flow oscillations were observed under certain conditions, which were accompanied by instabilities and flow reversals. Reasonable agreement (±30 percent) is obtained between the analytical and experimental results.

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“…PWR nuclear power plant data was introduced [14][15]. These data primarily consist of the temperatures of the hot and cold legs, the pressures of the primary coolant, and the pressures and water levels of the pressurizer and secondary sides of the steam generators.…”

Section: Introductionmentioning

confidence: 99%

Natural Circulation in a PWR for a Sinusoidal Heat Input: Analytical Model

Abdulrahman¹

2022

Proceedings of the 8th World Congress on Mechanical, Chemical, and Material Engineering

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Natural circulation is a crucial passive heat removal process for all light water reactors. To understand the consequences of decreasing primary coolant inventory on natural circulation, an analytical one-dimensional model has been developed for a sinusoidal input heat distribution, based on solutions to the continuity, momentum and energy equations and expressions for the natural circulation parameters have been derived for PWR plant. The model encompasses all potential types of natural circulation (single-phase, combined single and two-phase, and two-phase). In this paper, it is found that the transition between the different modes of natural circulation with various system inventories is smooth. As the flow mode changes from single-phase (100% mass inventory) to two-phase natural circulation, the loop mass flow rate increases and exhibits a peak within a narrow band of inventory (usually between 60-80%). Also, it is demonstrated that natural circulation in a PWR type system can provide an effective mechanism for the rejection of core decay heat to the secondary over a primary coolant inventory range of 100 to 60%, and a core decay power range of 1.5 to 5% of full power. Comparisons are made between pervious experimental results and prior research and the analytical outcomes are found to be in reasonable accord.

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Experimental Study of the Transition from Forced to Natural Circulation in EBR-II at Low Power and Flow

Cited by 10 publications

References 0 publications

Investigation of combined free and forced convection in a 2 x 6 rod bundle during controlled flow transients

Investigation of combined free and forced convection in a 2 x 6 rod bundle during controlled flow transients

Experimental and Analytical Investigation of a Natural Circulation System with Parallel Loops

Natural Circulation in a PWR for a Sinusoidal Heat Input: Analytical Model

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