The twenty-seventh volume of the Thermophysics series is devoted to investigating 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 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 programmes 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 information obtained will improve 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 the results of experimental investigations, conducted by the author together with Dr. I. Kolesnikov and Dr. A. Salauskas.