The Increase of Efficiency of Bundle of a Circular Finned-tubes with Change of Shape and Geometrical Parameters in Turbulent Flow

In this paper, the increase of efficiency of a compact bundle of finned tubes with circular cross-section used in Shell and Tube heat exchanger are studied. For this purpose, first we study the change of cross-section of one of the rows of without fin tube bundle with an elliptical tube in turbulent flow and investigate the effect of diameter and longitudinal pitch length on the performance of the bundle. Next, we investigate the effect of fins on the performance the bundle. The SST k-ω method is used for turbulence. In tubes with a diameter of 0.02 m, the efficiency increase is about 21%, when altering the fifth row. By reducing the diameter of the pipes to 0.015 m, while longitudinal step length is kept unchanged, it can be seen that the fourth row has more efficiency than the rest (about 31% with an increase in diameter of up to 0.024 m) the alternation of the sixth row boosts performance by about 6%. By decreasing and increasing longitudinal step length, the efficiency is increased by 35%, and 18%, respectively in diameter 0.02m. As a result, it can be said that increase of efficiency depends on both pipe diameter and longitudinal step length, But diameter changes has greater impact on choosing the best row. Also, mixed circular and elliptical tube bundles with circular fins increase efficiency 11% and 12% with diameter of 0.02m and 0.024m, respectively, in comparison to full circular finned-tubes bundle