HEAT TRANSFER INTENSIFICATION IN THE TUBES WITH CORRUGATED INSERTS OF “BLOCKING UP” TYPE

Abstract

Numerical simulation of the thermal and hydraulic characteristics of the flow in the initial sections of tubes with corrugated inserts “blocking up” the cross section of the tube was carried out. The structure of the flow and the process of disturbance`s generation with a concomitant change in heat exchange at different degrees of clamping of the tube cross section in the range of transitional Reynolds numbers are investigated. The change in the thermal and hydraulic characteristics of tubes with corrugated inserts was shown depending on the degree of cross section local blocking and the Reynolds number in the considered ranges of geometric parameters in a transient flow regime. The features of the disturbances formation in the flow and their relationship with the energy efficiency of the heat exchange surface`s structuring were considered. The influence of the Reynolds number on the stagnant fluid zone formation in the goffers of considered amplitude and length ratio, as well as the effect of this zone on heat exchange processes, was determined. A comparison of the heat transfer intensity and the hydraulic resistance values of partially corrugated tubes with similar parameters in smooth tubes was made. The effect of perturbation generation beginning on the energy efficiency of tubes with a partially corrugated surface compared to smooth tubes in the range of transition Reynolds numbers was shown. The threshold values of the parameter k = a 2 / R 0 and the Reynolds number, at which it is possible to achieve the highest heat transfer intensity with minimal hydraulic losses in the considered range of Reynolds numbers, Prandtl numbers and geometrical parameters were determined.