In order to improve the heat transfer enhancement of serrated spiral-finned-tube

twisted-serrated spiral finned tube was fabricated by changing the deflection angle and the twisted direction of serration. Twisted-serrated spiral finned tube banks with the diameters of 38 mm and 51 mm were researched by numerical simulation combined with modeling experiments. The influence of fin pitch on heat transfer and resistance characteristics of twisted-serrated spiral finned tube was obtained. The results showed that Nu at air-side increased firstly and then decreased with the increase of fin pitch from 3.63—8.47 mm. The effects of fin pitch on Nu at air-side was weaker when the fin pitch was larger than 6.35 mm. Eu at air-side decreased with increasing fin pitch. For twisted-serrated spiral finned tube banks with the diameters of 38 mm and 51 mm

comprehensive performance index Nu·f-1/3 was the maximum when the fin pitch is 6.35 mm. Thus

Pf =6.35 mm was the optimum fin pitch within the range of 3.63—8.47 mm.