Pool boiling performance of gyroid-structured surfaces subject to R-1233zd(E) refrigerant

This experimental study investigates the pool boiling heat transfer performance of the low-GWP refrigerant R-1233zd(E) on additively manufactured triply periodic minimal surface (TPMS) gyroid lattice surfaces. Two gyroid configurations, with unit cell sizes of 1 mm (GL-1) and 1.2 mm (GL-1.2), were examined and compared with a well-polished copper surface having an average roughness of 0.025 μm. Experiments were conducted at saturation pressures of 1.5, 2.0, and 2.5 bar under both increasing and decreasing heat flux conditions. The results show that gyroid lattice structures significantly enhance pool boiling heat transfer by improving liquid replenishment, separating vapor and liquid pathways, delaying lateral bubble coalescence, and promoting bubble detachment from the heated surface. At low heat flux under increasing heat flux conditions and 1.5 bar saturation pressure, GL-1 and GL-1.2 achieved HTC enhancements of approximately 582% and 183%, respectively, compared with the smooth surface. Under decreasing heat flux conditions at the highest heat flux and the same pressure, the corresponding HTC enhancements were 105% and 112%. The reason for this improvement lies not only in the lattice-structure-enhanced surface but also in the fabrication process. The study also revealed different boiling hysteresis behavior between smooth and gyroid surfaces. For the smooth surface, HTC was higher during decreasing heat flux operation, whereas the gyroid surfaces showed better performance during increasing heat flux operation. Considering the confinement effect, and area-related efficiency the hystersis phenomena was investigated. As the saturation pressure increased, the difference between increasing and decreasing heat flux conditions decreased, indicating suppression of boiling hysteresis. At the highest tested heat flux of approximately 215 kW·m −2 and 2.5 bar, GL-1 and GL-1.2 achieved maximum HTC enhancements of 85% and 101%, respectively.