Abstract:

In this paper,first,the heat transfer and flow resistance characteristics of 98% sulfuric acid in the converging-diverging tubes inserted with twisted tapes are numerically simulated,and the corresponding heat transfer effect are compared with that in the smooth tube and in the single converging-diverging tube. Then,the effects of flow state and thermal physical property on the comprehensive heat transfer performance of the converging-diverging tubes inserted with twisted tapes are analyzed,and the field synergy between velocity and heat flow fields is discussed. The results indicate that the comprehensive performance of the converging-diverging tubes inserted with twisted tapes are higher than that of the single converging-diverging tube under laminar flow,while are lower under turbulent flow,that small twist ratio of twisted tapes is beneficial to the improvement of the comprehensive performance under laminar flow,while large twist ratio is beneficial under turbulent flow,and that the synergetic enhancement
of the heat transfer by the twisted tapes is more significant under laminar flow than that in turbulent flow. In addition,in heat exchangers of converging-diverging tubes inserted with twisted tapes,the fluids with low and very high viscosity are of better heat transfer performance than that with medium viscosity.

Key words: heat transfer enhancement, converging-diverging tube, twisted tape, sulfuric acid, field synergy