Abstract:

The shell- side heat transfer and flow characteristics of self- supported rectangular converging- diverging tubes with different inserts (torus and baffle plate) were numerically simulated in a turbulence state with the Rey-nolds number varying from 27900 to 41900,and the results were compared with those without inserts.It is found that the insertion of torus and baffle plate results in the variations of velocity and temperature distribution in the channel and consequently leads to different heat transfer and flow characteristics,that the shell- side heat transfer coefficients of the two enhanced tubes respectively increase by 16.69%～24.32% and 38.01%～46.74% after the insertion,with the associated pressure drop increments achieving 74.02%～89.50% and 68.49%～87.16%,respectively,and that the tube with baffle plate is of the best overall shell- side heat transfer performance,while the baseline is of the worst.Moreover,it is indicated that the key to the heat transfer enhancement of a heat exchanger is to improve the heat transfer of the converging- diverging tube on the two sides of the channel,and that,from the viewpoint of field synergy principle,the reduction of the average intersection angle between the velocity vector and the temperature gradient is one of the essential factors to enhance the heat transfer performance.

Key words: self- supporting, converging- diverging tube, heat transfer enhancement, insert