Numerical study of laminar flow and heat transfer characteristics in the fin side of the intermittent wavy finned flat tube heat exchanger

The wavy finned flat tube heat exchangers are widely used in air-cooled condensers of power plants. The flow and heat transfer characteristics in the fin side of the wavy finned flat tube heat exchanger are numerically studied and compared with experimental results. The influence of the fin spacing, the wave spacing, the wave amplitude and Reynolds number on the flow and heat transfer performances is investigated. The correlations of the Nusselt number and friction factor are obtained by fitting the numerical results. The results show that the intermittent wavy fin can significantly increase the heat transfer than straight fin. The wavy channel of the intermittent wavy finned flat tube heat exchanger can produce the longitudinal vortices and the transversal vortices. The longitudinal vortices can enhance heat transfer, but the transversal vortices appear negative effect on heat transfer. Both of the intensities of longitudinal vortices and transversal vortices do not uniquely determine Nusselt number for all configurations. The suggestions for improving the heat transfer performance in the fin-side of intermittent wavy finned flat tube are obtained. That is, the fin spacing is 3.0 mm, the wave spacing is 9.5 mm and the wave amplitude is 2.3 mm.