Experimental researches of thermal hydraulic characteristics in the model of sodium$air heat exchanger for fast reactor emergency cooling system

UDC: 
УДК 621.039.526

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Abstract: 

Results of experimental researches of thermohydraulic characteristics in the bundle of finned tubes are presented in the paper. The test section represents a fragment of flow part of sodium-air heat exchanger in the emergency cooling system of a fast reactor, with sodium flow inside the tubes and cooled by lateral flow of air. A great data array of temperature values on the finned tubes surface at different air velocities and hydraulic characteristics of finned tube bundle were gained. Experimental data on heat transfer were processed in two ways: first, on the basis of direct measurements of temperatures on the surface of a finned tube and air flow and, secondly, on mean value of heat transfer coefficient of tube bundle. Analysis of experimental data has shown that a divergence of both approaches does not exceed 19%.
It was found in the tests that the heat flow removed from a finned tube’s surface with a finned surface factor being equal to 7.2 is 3–5 times more intensive than that from smooth surface. In the course of the experiments air overheating was noticed in the intertubularspace in the direction of air flow. Most likely, it is due to formation of stagnant zones caused by small interfin spaces and heat accumulationduring long warming up of the sodium circuit. Experimental data can be used for verification of thermal hydraulic numerical codes for sodium-air heat exchanger in the emergency cooling system of fast reactors. The experimental results application to a full-scale facility is substantiated. Power estimations of a full-scale heat made with regard to the value of experimental heat transfer coefficients have shown that heat removal can be lower (depending on the velocity of air flow) than claimed in the design.

References: 
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