Experimental investigations of thermal hydraulic properties of coolant flow in experimental models of fuel assemblies (FA) were performed. FA models with 7, 19 and 37 pins in hexagonal arrangement were used as test sections. Friction loss coefficients of smooth rod bundles are presented and compared. Hydraulic resistance of spacing grids with different geometry is discussed. Comparison of obtained data with correlations of Rehme and Idelchik is carried out. Averaged heat transfer dependences on distance from spacer grid top end are presented and compared with different dependences. Experimental results for coolant velocity distribution in subchannels of experimental models were obtained using both Pitot pipe technique and laser Doppler annemometry (LDA). It was shown that a strong disturbance of the flow just behind the spacer grid is present. The flow stabilization occurs at relatively small distances from the spacer elements.

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