UPTF test results: First three separate effect tests

Abstract. The paper covers the results of VVER core reflooding studies in fuel assembly (FA) mockup of 126 fuel rod simulators with axial power peaking. The experiments were performed for two types of flooding. The first type is top flooding of the empty (steamed) FA mockup. The second type is bottom flooding of the FA mockup with level of boiling water. The test parameters are as follows: the range of the supplied power to the bundle is from 40 to 320 kW, the cooling water flow rate is from 0.04 to 1.1 kg/s, the maximum temperature of the fuel rod simulator is 800°C and the linear heat flux is from 0.1 to 1.0 kW/m. The test results were used for computer code validation.

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“…This agrees well with the conclusions of the experiments in the UPTF facility [17,18] in Germany, where no flow choking was observed.…”

Section: Discussionsupporting

confidence: 92%

A study of different cases of VVER reactor core flooding in a large break loss of coolant accident

Bezrukov

Schekoldin

Zaitsev

et al. 2016

EPJ Nuclear Sci. Technol.

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“…The working fluid is water with a bulk temperature of 300 K at atmospheric pressure, a condition that can occur during the LBLOCA. The wall temperature range is shown in Table 11, assuming that the single-phase mixed convection correlations are applied where the wall temperature is lower than 373 K. The characteristic length D h is chosen with reference to the UPTF experiment [52]: a 1 : 1 representation of a PWR primary system. Table 11 shows the Grashof number ranges calculated from ΔT obtained by random sampling.…”

Section: Correlation Applicability To Conditionsmentioning

confidence: 99%

Opposing Mixed Convection Heat Transfer for Turbulent Single‐Phase Flows

Motegi,

Sibamoto,

Hibiki

et al. 2024

International Journal of Energy Research

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Convection, wherein forced and natural convections are prominent, is known as mixed convection. Specifically, when a forced convection flow is downward, this flow is called opposing flow. The objectives of this study are to gain a comprehensive understanding of opposing flow mixed convection heat transfer and to establish the prediction methodology by evaluating existing correlations and models. Several heat transfer correlations have been reported related to single-phase opposing flow; however, these correlations are based on experiments conducted in various channel geometries, working fluids, and thermal flow parameter ranges. Because the definition of nondimensional parameters and their validated range confirmed by experiments differ for each correlation reported in previous studies, establishing a guideline for deciding which correlation should be selected based on its range of applicability and extrapolation performance is important. This study reviewed the existing heat transfer correlations for turbulent opposing flow mixed convection and the single-phase heat transfer correlations implemented in the thermal–hydraulic system codes. Furthermore, the authors evaluated the predictive performance of each correlation by comparing them with the experimental data obtained under various experimental conditions. The Jackson and Fewster, Churchill, and Swanson and Catton correlations can accurately predict all the experimental data. The effect of the difference in the thermal boundary conditions, i.e., uniform heat flux and uniform wall temperature, on the turbulent mixed convection heat transfer coefficient is not substantial. The authors confirmed that heat transfer correlations using the hydraulic-equivalent diameter as a characteristic length can be used for predictions regardless of channel-geometry differences. Furthermore, correlations described based on nondimensional dominant parameters can be used for predictions regardless of the differences in working fluids. The authors investigated the extrapolation performance of the mixed convection heat transfer correlations for a wide range of nondimensional parameters and observed that the Jackson and Fewster, Churchill, and Aicher and Martin correlations exhibit excellent extrapolation performance with respect to natural and forced convection flows, indicating that they can be applied beyond the parameter range validated experimentally.

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“…Unfortunately, no detailed measurement data were available. Therefore only a qualitative comparison of the flow behavior and temperature distribution of the experiment [5] and the CFD calculation was performed.…”

Section: Uptf Test Imentioning

confidence: 99%