# Heat Transfer and Hydrodynamics in Gas-Cooled Fuel Rod Assemblies

## Beschreibung

The twenty-seventh volume of the Thermophysics series is devoted to investigations of heat transfer, hydrodynamics and flow mixing in gas-cooled fuel rod assemblies in longitudinal flow with a marked change in geometric characteristics of the cells along the assembly radius. The investigations were conducted at the Lithuanian Energy Institute for a number of years. The book presents data of the experimental and theoretical study of local heat transfer and hydrodynamics in assemblies of smooth and rough rods, spaced using honeycomb spacer grids. Alongside assemblies with spacer grids consideration was given to assemblies with a wire winding.

Extensive experimental data made it possible to develop a number of universal calculating procedures and programs for the analytical cell-by-cell calculation of heat transfer and hydrodynamics in assemblies in longitudinal flow, the calculation of shear stresses at the wetted surfaces of assemblies, and the determination of local resistances of honeycomb spacer grids.

The integrated numerical and experimental study of thermohydraulic characteristics provided an explanation of some specific features of heat transfer and hydrodynamics in such complex systems. The obtained information is needed for improving the reliability of operation of various modern gas-cooled heat-transfer devices and will be useful in developing fuel assemblies of new nuclear reactors with various coolants.

The monograph incorporates results of experimental investigations, conducted by the author together with Dr. I. Kolesnikov (Parts 5 and 6) and Dr. A. Salauskas (Parts 6 and 7).

238 pages © 2005

## Inhaltsverzeichnis:

1.1 Analysis of methods of the thermohydraulic calculation of rod assemblies

2 Thermohydraulic calculation rod assembly (DARS) program

2.2 Calculation of cross flows of the coolant

2.3 Model of the spacer grid

2.4 Determination of the wall temperature of the rod

2.5 Construction of the DARS program

2.6 Approbation of the algorithm of the DARS program

3 Calculating procedures for hydraulic resistance of spacer grids

3.1 Average calculations models

3.2 Cellular calculation model for the spacer grid implemented in the SPATES program

3.3 Cellular model of calculating the spacer grid, implemented in the DIR program

4 Models of calculation of shear stresses

4.1 Model of calculation of the shear stresses implemented in the RKN program

4.2 Model of calculating of the sheat stresses implemented in the RKN-M program

5.3 Data processing procedure

6 Experimental data and their comparison with calculated results

6.2 Shear stresses and velocity fields

6.3 Distribution of the coolant velocities and flow rates over the assembly cross section. The hydraulic resistance of elementary cells

6.4 Calculation of the shape factors of elementary cells

6.5 Effective coefficient of turbulent mixing

6.6 Heat transfer in bundles in longitudinal flow

7 Flow structure in the assembly of rods with wire wrapping

8 Main conclusions and practical recommendations

8.1 Hydraulic resistance of fuel assemblies

8.3 Effective coefficient of turbulent mixing of flow

8.4 Heat transfer of fuel rod assemblies in flow