Microstructure fabrication and flow boiling enhancement of R245fa in dendritic and spherical copper powder tubes

To investigate the influence of porous structure morphology on enhanced flow boiling heat transfer in tubes, two types of porous-structured tubes were fabricated using 100-mesh copper powder particles with distinct morphologies through a sintering-electrochemical deposition coupling technique: dendritic copper powder surface-enhanced tube (D-SET) and spherical copper powder surface-enhanced tube (S-SET). Experimental studies demonstrate that D-SET exhibits exceptional heat transfer performance. Its maximum heat transfer coefficient reaches 16.26 kW/(m2 K), which is 1.10 times that of the S-SET. Comparative results show that the performance evaluation criterion (PEC) of the D-SET surface is 12% higher than that of the S-SET. The maximum PEC of D-SET reaches 2.72, exceeding the value of the spherical surface. The performance enhancement is attributed to the branched microstructures formed by dendritic copper powder. These structures improve bubble dynamics and delay dryout, which strengthens phase-change heat transfer. Although the pressure drop increases by 12.3%, the D-SET surface still shows superior overall thermal performance. The results confirm that copper powder morphology plays a key role in controlling surface heat transfer. They also offer guidance for the design and application of microstructured surfaces in high-efficiency thermal management systems.