Experimental study on the influence of convex structures of a single vertical fin on condensation and frosting under constrained airflow conditions

Uniform frosting on the surface of finned heat exchangers in low temperature and high humidity environments can help alleviate the performance degradation of air source heat pumps. Traditional research has mostly focused on system defrosting strategies and optimization of surface wettability of fins, without paying attention to the study of uniform frosting on individual fins. This study proposes a new strategy aimed at inducing uniform frosting on fins by designing convex structures on the surface of the fins. Through systematic experimental observation, the influence of convex structures with different geometric shapes on the full cycle process of condensation and frost growth was studied. The research results indicate that due to the influence of edge effects and center temperature, droplets and frost on the surface of fins without convex structures are distributed in a W-shaped pattern along the airflow direction. At 60 minutes, the non-uniformity of condensate droplet coverage and frost thickness was 11.3% and 0.023 mm, respectively. The effect of inducing condensation and frosting was significant after adding the protruding structure, but it would block the leeward airflow and suppress condensation and frosting. The non-uniformity of droplet coverage of the vertical linear convex structure fins was reduced by 25.0%. After adding the edge convex structure, the gap is less likely to enter humid air, and the non-uniformity of frosting increases by 26.2%. This study can provide important theoretical basis and innovative technological path for the design and management of surface convex structures during frosting process.