Fin-tube heat exchangers are widely used in building energy systems. Their performance can be limited by the relatively high fin-tube thermal contact resistance and its propensity to initiate galvanic corrosion. Therefore, most commercial fin-tube heat exchangers use tube expansion or brazing to ensure intimate contact is established between the fins and tubes. However, expansion results in manufacturing complexity and mechanical damage to internal heat-transfer-enhancing features within the tube, while brazing increases manufacturing complexity and may cause interfacial reactions. In this work, a selective nickel-electroplating (NEP) strategy was developed to locally bridge copper tubes and aluminum fins through nickel deposition at the joint interface. The selective NEP method is done at room temperature and eliminates the need for tube expansion or brazing. The joint quality, heat transfer performance, and corrosion durability of fabricated prototype heat exchangers using selective NEP were systematically evaluated and compared with heat exchangers fabricated using thermally conductive adhesive bonding and full-surface NEP. Selective NEP significantly reduces the total thermal resistance by more than 70% compared to the adhesive-bonded heat exchanger under dry conditions. Under frosting conditions, the total thermal resistance of the selective NEP heat exchanger decreases by 40% when compared to an adhesively bonded counterpart. Extended exposure to cyclic acidified salt-fog environments (ASTM G85 A3, SWAAT) revealed that the selective NEP heat exchanger maintains excellent structural integrity and corrosion resistance. The selective NEP method enhances fin–tube joint strength by more than threefold relative to adhesively bonded configurations. These results demonstrate that selective NEP provides a low-temperature, mechanically robust, low thermal contact resistance, and corrosion-resistant joining strategy for fin-tube heat exchangers. • Selective nickel electroplating (NEP) developed to form robust tube-fin joints. • Selective NEP allows elimination of tube expansion or tube-fin brazing. • Thermal resistance reduced by 70% (dry) and 40% (frosting) using selective NEP. • Selective NEP demonstrates corrosion resistance after prolonged ASTM G85 A3 tests. • NEP joints show strong shear strength of tube-fin joints.
Zhang et al. (Sun,) studied this question.