Investigation into the efficiency of a fin and wound wire intensifier

The work continues the experimental investigations into heat transfer enhancement carried out at NIU MPEI. To verify the obtained results and extend the range of geometric characteristics of the intensifier, additional systematic experiments were performed. The investigations were carried out under the program of improvement of existing water-cooled water-moderated reactors to create a base of reliable experimental data and design correlations that could be required in developing reactors of the fourth generation. Among the methods for improving the safety of the core and of the overall reactor is the replacement of conventional fuel rods in fuel assemblies with tubular ones and development of spacers that best suit fuel assemblies. A design of an intensifier that can be used in a spacer grid is examined. A brief description of the test section and the design of developed intensifiers with a list of their basic geometric characteristics are presented. New systematic experimental data are given on hydraulic resistance factors and heat transfer coefficients for single-phase convection with the use of a fin-and-wound wire intensifier. This investigation extends the range of intensifier geometric characteristics and operating conditions: the mass flow rate range was ρw = 1000–4000 kg/(m² s), the pressure range was p = 3.0–7.0 MPa, the coolant temperature at the test section inlet was 100°C, and the heat flux range was q = 0.23–0.70 MW/m². The experiments revealed a considerable increase in the heat transfer coefficient on the convex heated surface and dependence of the hydraulic resistance factors and the heat transfer coefficients on the wire winding pitch. The relative pin heights offering a higher increase in heat transfer as compared with an increase in hydraulic resistance were established. Empirical correlations for predicting the heat transfer coefficients and the hydraulic resistance factors as a function of the intensifier geometric characteristics are proposed.