The issue of heat transfer enhancement is analyzed for the widely existed problem of the low heat transfer coefficient of laminar convective heat transfer in tubes. A new type of tube with variable cross-section is introduced under the directions of the heat transfer enhancement principles. Models of new tubes with variable cross-section under different parameters and general round tube are established. With large CFD analysis software FLUENT

and the influence on laminar convective heat transfer in tubes of new variable cross-section heat exchange tubes are investigated. Results show that the new tubes with variable cross-section could markedly enhance the laminar convective heat transfer of the tube side with less additional increase of flow resistance

and has a better synthetic performance of heat transfer enhancement. Within the scope of this study

Nu and η of new heat tubes both increase with the decrease of L1/di or L2/di

and η of new heat tubes is greater than 2.22. The results provide a certain guidance and theoretical basis for the enhancement of laminar convective heat transfer in tubes.