Thermal performance of a boiling and condensation enhanced heat transfer tube-stepped lattice finned tube

It is a challenging job to develop a finned tube that possesses highly efficient condensation as well as boiling heat transfer enhancement. A stepped lattice finned tube (SLFT) with two layers of staggered fins produced on the side wall of spiral grooves of tube surface is designed and fabricated to achieve the goal. The overall heat transfer performance, shell side and tube side heat transfer performance of the SLFT in condensation and boiling conditions are experimentally investigated at the flow velocity ranging from 1 m/s to 3 m/s. The overall condensation and boiling heat transfer coefficients of the SLFT are up to 8.1 times and 5.1 times that of the smooth tube, respectively. Compared with other reported enhanced tubes, the SLFT has better condensation and boiling heat transfer performance. The SLFT with moderate pitch, small step height and small width possesses better condensation heat transfer enhancement whereas the SLFT with large pitch, large step height and moderate width possesses better boiling heat transfer enhancement. The SLFT with superior heat transfer enhancement under both condensation and boiling conditions provides a promising solution to highly efficient and compact heat exchanger integrated refrigerating and heating.