EXPERIMENTAL AND NUMERICAL INVESTIGATION OF HEAT TRANSFER AND PRESSURE DROP IN STAGGERED ARRANGEMENT HELICALLY FINNED-TUBE BUNDLE

摘要

In a new pressurized water reactor nuclear power plant, the heat exchange tube bundle of the Moisture Separator Reheater (MSR) is a new designed staggered arrangement low helically finned-tube bundle. To investigation the thermal hydraulic characteristics of the Reheater part of MSR, the tube bundle test section was designed by using prototype tube and prototype arrangement of the new designed MSR. The experiment was carried out on the test section with steam cross-flowing outside the horizontal tube bundle, same conditions as MSR' operation designing , and electrical heating in the tubes simulating the condensation heat release of the two phase-flow inside. A lot of experimental data on heat transfer and pressure drop were obtained in a broad experiment parameters range of wall heat flux density and steam temperature, pressure and Reynolds number. Based on the present data, empirical average heat transfer correlation and friction factor correlation were proposed for the outside average heat transfer and pressure drop. Comparisons and analysis between these experimental results and some of other investigations were made. The conclusions of this experimental investigation were given. The results are very useful to the design of the heat exchange tube bundle in the MSR, and the validations of the new design. However, experimental studies cannot adequately reveal the detail of flow characteristics, and suitable correlations for this fin geometry are very rare. Thus, numerical simulations should be performed to make up for the deficiency. To perform a detail understanding of the heat transfer and pressure drop characteristics, a three-dimensional geometry was carefully constructed and a fine mesh was generated. The flow across the tubes was assumed to be a steady, incompressible turbulent flow. RNG based k-ε turbulence model was chosen in the simulation. Nusselt number and Euler number of a wide range of Reynolds numbers (based on the steam velocity through the minimum flow area) from 1 ×10~4 to 8×10~4 were calculated by the CFD software ANSYS Fluent. The numerical results were compared with experiment results of the same fin geometry and tube configuration. Also, local flow behavior and local temperature distribution were obtained to show the detail flow features and heat transfer. The velocity and temperature distribution near the fin surface were discussed