Reactor fuel elements generally consist of rod bundles with the coolant flowing axially through the bundles in the space between the rods.Heat transfer calculations form an important part in the design of such elements, which can only be carried out if information of the velocity field is available.A one-equation statistical model of turbulence is applied to compute the detailed description of velocity field (axial and secondary flows), the wall shear stress distribution and the friction factor of steady, fully developed, turbulent flows with incompressible, temperatureindependent fluid, flowing through triangular arrays of rods with different aspect ratios (P/D).Also experimental measurements of the distributions of the axial velocity, turbulence kinetic energy and Reynolds stresses were performed using a laser Doppler anemometer (LDA), operating in a "fringe" mode with forward scattering, in a simulated interior subchannel of a triangular rod array with P/D=1.123

Heat exchangers consisting of finned tubes are commonly employed in air conditioning systems, air heaters, radiators, etc. Local measurements of mass transfer coefficients on fins, obtained by Saboya and Sparrow, are very nonuniform. In the present work, an experimental apparatus was set up to measure overall heat transfer coefficients for two-row tube and plate fin heat exchangers. The obtained results, together with Shepherd’s results for one-row exchangers, are used to transform the local mass transfer coefficients into local heat transfer coefficients. A numerical two-dimensional heat transfer analysis has been performed in order to obtain the temperature distribution and fin efficiency. The influences of the Reynolds number and fin material are also analyzed.

No abstract

The fuel element of LMFBR consists of a bundle of rods wrapped with an helical wire as spacer, surrounded by an hexagonal duct. In the present work, a semi-empirical model is developed to calculate bundle average and subchannel based friction factors and flow redistribution. The obtained results were compared to experimental data and they were considered satisfactory for wide range of geometrical parameters

No abstract