Experimental and numerical study and comparison of performance for herringbone wavy fin and enhanced fin with convex-strips in fin-and-tube heat exchanger

In this paper, a new kind of herringbone wave fin with convex-strips in fin-and-tube heat exchanger is experimentally and numerically studied. For comparison, a herringbone wave fin surface with the same dimension in fin-and-tube heat exchanger was also investigated. Four heat exchanger samples in staggered arrangement are tested: the herringbone wavy fin with two and three rows (F-W2 and F-W3) and the convex-strips herringbone wavy fin with two and three rows (F-C2 and F-C3). At low velocities (2.5 m/s for two rows and 2 m/s for three rows), the heat transfer coefficients of F-C2 and F-C3 increases by 6.6% and 4.6% compared to that of F-W2 and F-W3, respectively. And the pressure drops are correspondingly increased by 7.5% and 8.0%. At higher velocities (4.5 m/s below), 8.2% and 6.5% promotions for the heat transfer coefficients of F-C2 and F-C3 are achieved, respectively. And the pressure drops are correspondingly increased by 11.0% and 10.9%. Correlations of the Nusselt number Nu and friction factor f on the air side are summarized. Numerical results indicate that the induced vortices near the tube wall are the main reason for the enhancement of heat transfer performance. The performance evaluation plot is adopted to describe the comprehensive performance of the four heat exchangers.