Effect of geometric size of curved delta winglet vortex generators and tube pitch on heat transfer characteristics of fin-tube heat exchanger

•Curved delta winglet vortex generator (CDWVG) is experimentally studied.•CDWVG can effectively enhance the heat transfer performance.•Fin pitch has less effect on Colburn factor but obviously affects friction factor.•Decreasing the tube pitch is beneficial to heat transfer enhancement. Vortex generator has received extensive attention and was widely applied for heat transfer enhancement. In order to further improve the heat transfer performance of compact heat exchanger, curved delta winglet vortex generators with different geometric sizes are experimentally studied for circular tube-and-fin heat exchanger in this paper. A total of 15 samples of circular tube-fin exchanger with three fin pitches, two tube pitches and two sizes of curved delta winglet vortex generators with different base length are carried out to find their effect on heat transfer and pressure losing. Colburn factor and friction factor are used to evaluate the performance of circular tube-and-fin heat exchanger with different parameters. The results showed that smaller vortex generator which locates close to the tube has the advantageous to heat transfer enhancement for flow with low Re and the larger vortex generator is more conducive to heat transfer enhancement for flow with large Re. The change of fin pitch has less effect on Colburn factor while friction factor is obviously affected by the change of fin pitch. Decreasing the tube pitch is beneficial to the heat transfer at the cost of increasing pressure loss and the overall heat performance increases when fin pitch is 2.3mm.