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Cooling of the core in fast neutron reactors in accident conditions (ULOF, UTOP) leads to the study of regimes with reduced coolant flow rates or during natural convection in fuel assemblies. The results of experiments on heat exchange and the stability of circulation during boiling of a sodium and sodium-potassium alloy on the models of single and in a system of parallel fuel assemblies with natural coolant circulation are presented. It is shown that the boiling process of liquid metals in fuel assemblies has a complex structure, is characterized by both stable and pulsating regimes with significant fluctuations in flow rate, pressure, temperature, and the occurrence of a heat exchange crisis. The hydrodynamic interaction of the circulation contours can lead to a significant increase in the amplitude of fluctuations in the coolant flow rate in them ("resonance" of flow rate pulsations) and a possible "blocking" or inversion of the coolant flow rate, an increase in the temperature of the coolant, and the cladding of the fuel elements (interchannel instability effect) and crisis. The data of calculated and experimental studies of the liquid metal boiling in FA models are compared. The effect of the surface roughness of the fuel rods on the heat exchange and flow regimes during a liquid metal boiling in bundles is demonstrated. It has been shown experimentally that there is no steaming of the sodium cavity and no change in the boiling regime in the fuel assembly when a sodium cavity is located in a fuel assembly designed to compensate for the positive sodium void reactivity effect during sodium boiling. There is the possibility of continued cooling of the fuel elements in the fuel assembly. The data on heat exchange during boiling of liquid metals in bunches are generalized, and a cartogram of the flow regimes of a two-phase flow of liquid metals in bundles is constructed that differs significantly from the cartogram for water. The boundaries between flow regimes are approximated by simple dependencies. [ABSTRACT FROM AUTHOR]

Abstract: Coordinated Ocean-ice Reference Experiments (COREs) are presented as a tool to explore the behaviour of global ocean-ice models under forcing from a common atmospheric dataset. We highlight issues arising when designing coupled global ocean and sea ice experiments, such as difficulties formulating a consistent forcing methodology and experimental protocol. Particular focus is given to the hydrological forcing, the details of which are key to realizing simulations with stable meridional overturning circulations. The atmospheric forcing from [Large, W., Yeager, S., 2004. Diurnal to decadal global forcing for ocean and sea-ice models: the data sets and flux climatologies. NCAR Technical Note: NCAR/TN-460+STR. CGD Division of the National Center for Atmospheric Research] was developed for coupled-ocean and sea ice models. We found it to be suitable for our purposes, even though its evaluation originally focussed more on the ocean than on the sea-ice. Simulations with this atmospheric forcing are presented from seven global ocean-ice models using the CORE-I design (repeating annual cycle of atmospheric forcing for 500 years). These simulations test the hypothesis that global ocean-ice models run under the same atmospheric state produce qualitatively similar simulations. The validity of this hypothesis is shown to depend on the chosen diagnostic. The CORE simulations provide feedback to the fidelity of the atmospheric forcing and model configuration, with identification of biases promoting avenues for forcing dataset and/or model development. [Copyright &y& Elsevier]

• A novel method is used to get particle velocity and recirculation ratio. • Cyclone negative pressure and circulation stability are closely related. • The longest time lag may be the recirculation ratio and boiler load. • The recirculation ratio can characterize the boiler load changes in advance. A novel particle image trajectory method was developed to determine the velocity of particles entering a cyclone particle separator in a typical circulating fluidized bed (CFB) incinerator burning biomass and industrial waste. Based on particle velocity, the mass recirculation ratio was calculated to characterize the fluidization stability, and its key factors were quantitatively discussed. The results indicated that the proposed method can determine the particle velocity and recirculation ratio rapidly and accurately, and the relative errors of velocity calculation were 4.07 % and 0.04 %. The time lag between the recirculation ratio and the cyclone negative pressure, furnace temperature, and secondary air was 20–70s. We observed that the cyclone negative pressure was most likely related to circulation stability after eliminating the time lag. The longest time lag was between the recirculation ratio and boiler load, which was 230 s. The correlation between the recirculation ratio and boiler load improved (0.220) after the time lag was eliminated. Furthermore, the recirculation ratio could characterize changes in the boiler load in advance and provide predictive information for boiler load feedback control, which can be useful for monitoring and controlling incinerator combustion. [ABSTRACT FROM AUTHOR]